Honda auto transmissions (1998 - 2006) have been a weak link in what should be a great car. This company prides itself on reliability? At least Honda America extended the warranty on transmissions whereas Honda Australia would have you believe that a rebuild or replacement on a 7 year old car (time of writing) at 18,000 miles to 43,000 miles is normal wear and tear.
Some history, problems and causes.
Honda Motor Co. widened a recall of vehicles in the U.S. and Canada and other locations to 1.14 million units, among its largest, covering Accord and Acura cars that have the same transmission fault that triggered a light-truck recall this year.
The problem results from insufficient lubrication of a transmission shaft that can overheat, potentially damaging gear teeth or causing the gears to break, Honda said in a statement. In rare instances, this condition may lead to gear breakage and possible locking of the vehicle's transmission, creating a potential safety hazard.
Date: 03/08/2004
Supplier Name: Honda Australia Pty Ltd
Product Make: Honda
Product Model: Odessey EXV (V6) variant Accord V6 & V6L variants
Model Years From: 2000-2004
Consequences: Fractured components could lock the transmission possibly causing an accident. Campaign Number: 5CS
Just because you don't read about it on popular Australian forums does not mean that there is not a problem. There are numerous posts in Australia from frustrated owners who vow to never buy a Honda again. The stone-wall arrogant response from Honda Australia is usually the last straw.
If you have a design fault and you refuse to cover any failure outside the warranty period then at least offer a replacement transmission at cost price to the consumer instead of the greedy dealer mark-up price. This is not a plastic clip or disposable part, this is a huge unwarranted expense to the consumer because of Hondas ten year run of problems in these transmissions.
We don't sell the same volume of vehicles as America therefore we don't have the same volume of failures. It has been suggested that overseas outlets for Honda do not seem to be affected with SOME of the transmission problems of the American model. There are quite a few notifications to dealers that indicate certain assembly groups and build locations were, shall we say, a little shabby, and we may have been spared this extra line of faults, however design flaws are present in all locations.
What does not change is the fact that the design of the transmission and implementation of the clutch engagements logic is flawed.
We had the same recall in Australia for insufficient internal lubrication and cooling of the 2nd gear set in the five speed autos. We also have premature failure of transmissions because of a problem causing rapid wear of the clutch packs.
At the time of writing I see many, if not most of the Gen-7 Australian models, are only now reaching the mileage where these design failures start to occur. Do a search for the earlier models in Australia (1997- 2002) and you will find numerous complaints about automatic transmission failures. A substantial number of these cars have under 60,000km and most under 100,000km (62,000 miles) on the clock.
I find the attitude of some of the newer drivers (licensed less than 10 years) to the expected life of a motor vehicle quite ignorant. They have been bought up in a disposable society and believe that if a car has 100,000km on the clock (62,000 miles) that it is long in the tooth and ready to be scrapped. This same group think that if a vehicle is out of warranty that any inherent expensive design faults are not the responsibility of the maker. So if you travel 15,000km in four years and the transmission fails you should pay the $5,000 to $9,000 bill and quote - "Get over it".
It was only a few years ago that a car was considered "just run in" at 100,000km. I have owned three Australian made cars, two Nissan 260z's and a few American Big block fords, all bought with around 120,000km. They ran like new and needed no major service until over 200,000km. What caused the goal posts to be shifted so far for this current generation's attitude on quality and longevity?
If you expect less, then you can bet that politicians, car makers and dealers will give you just that - and charge you more for it. This information by Junior at http://www.vtec.net/ This is one of the best descriptions of the Auto that I have read anywhere.
Fundamentally for those who do not know, Honda's transmissions (and engines for that matter) are closely related to the race motors they are derived from. Being race-bred this technology spills over into the marketplace where everyone from your average Jane to Joe Rocket can sample and love or lump it. That said; let me formally introduce you to Honda's AT's. They are hydraulically actuated manual transmissions! What does this mean?
In a synchromesh manual transmissions (which is what cars marketed today are equipped with) all you ratios are in constant mesh fixed on one shaft while freewheeling on the other. Gear selection is accomplished by locking the freewheeling gear of the desired ratio to the shaft it's spinning on and voila! Your output is served. To make the transition between ratios smoother (as the different ratio gears are obviously turning at different speeds for a given shaft speed) clutch-like devices, known as "syncros" accel &/or decel gears in adjacent ratio pairs before the locks (dog clutches) engage.
Compared to your conventional epicyclical/planetary gear set automatic transmission, ratio selection is far easier, selection more positive and transmission design less complex for ratio addition. In view of this (and the fact that this conclusion had already been arrived at in racing circles, Honda devised and implemented a means of automating gear selection of their manual transmissions instead of lamely following convention.
Their efforts yielded the hydraulically actuated manual transmission found in all their AT equipped vehicles. "How did they achieve automation?" you may ask. Simple, by replacing the brass syncros with wet clutches, all they had to worry about was the ratio itself because clutch pack actuation was already a mastered technology.
The quirk to this transmission was that it had very positive shifts a consequence of wet clutches. Considered more of a boon than a nuisance to race teams, commuters found the shift quality rather alienating, especially since their previous exposure to AT's was limited to the forever-slipping-into-this-ratio-or-that conventional AT.
So the AHM charged to the rescue with soft shifting (read: longer slipping pre-engagement) transmissions. Of course slipping is not good for any clutch and a wet clutch is not excluded. So in '96.5, Honda introduced phased clutch engagement. This allowed for partial engagement of your 'to' gear before your 'from' gear was fully disengaged. This allowed for dramatically smoother shifts than previous models.
The ugly side to this advance was not to reel its ugly head for a couple of years. In late '97. DTC P0740- torque converter circuit failure- was discovered lurking somewhere in between the super-gizmo-wizardry of the PCM and the technologically advanced transmission.
Now early investigation found internal leaks &/or clogged valves to be the culprits. OK. We thought. But the shift quality still wasn't smooth enough. But before I get to what engineer's at AHM decided to do, let me ask you all a question.
How many of you have ever wondered why Honda has always (not now in the advent of flattering emulation by other marques) had 2 drive selections: D3 and D4? Hold that thought as we return to Honda's tranny refinery.
Realizing that pressure modulation was the key to shift shock reduction and that clutches would only stand for so much abuse, Honda looked to a formerly overlooked resource for addition shock dampening: the torque converter clutch. Formerly only used to positively lock the crank to the input shaft, Honda decided to phase its engagement in further efforts to make the AT's operation transparent. It worked for a while. But while existing problems brewed, a whole new batch was thrown in. 740's were jumping all so acrobatically out of the wood work and the more powerful power-trains fell first but their less endowed siblings were soon to follow suit.
While driving, the softer shifts were aggressively wearing away clutch material sometimes in particles that were trapped in screens and filters other times in smaller ones that made it through these lines of defence.
In the former situation, the internal filters (which by the way, are not serviceable) were clogged. This led to pressure loss, which exacerbated the transition duty of the clutches affected, essentially fuelling the vicious cycle's inferno of destruction. In the latter case, accumulation of deposits could occur in the fine passages of the valve body, in/on valve seats etc. Essentially depositing shit where it don't belong.
Now add to this the fact that you average commuter drives in D4 at speeds that equate to the threshold of TCC engagement, the mapped criteria of engagement coupled with the advanced partial engagement modes of the TCC you have a recipe for ATF & Clutch stew. That's an artery clogger if I ever saw one! (No pun intended!).
In so much as these transmission failures seemed to come out of the woodwork all at once, it was actually the accumulation of un-addressed undesirable operational consequences that all came to a head.
Now the newer 5-speed transmissions have the ignominy of having a third working geared shaft. Unfortunately, prolonged torture testing for reliability of this set wasn't long enough and internal lubrication and cooling weren't discovered until many owned vehicles with these ill-fated trannies in them. The fix: add point of correction cooling + lubrication by plumbing ATF to the problem. Hence the latest transmission recall in a seemingly endless stream of tranny woes. I must say one thing at this juncture. Redesign has rid the 5-spd transmissions of their heating problem.
Here's the deal on D4 and D3 gear selection that the driver has to make. Aside from the engagement (or not) of 4th gear or 5th gear (depending on the trans), the PCM is also mapped to lock up the torque converter at different engine loads and vehicle speeds.
The problem here is that this information is not relayed in any way shape or form to Honda owners. So here it is in terms you can use.
At the speeds, gear selection, and (I'm guessing here) average traffic conditions, you may feel a barely perceptible "shift" when you accelerate (for whatever traffic mandated reason) from your cruise speed. 'Grade logic', one of several fuzzy logics (designed to fine tune slight adjustable operating parameters to the driver's average driving habit(s)) is designed to prevent gear hunting - in this case between fourth (or fifth gear) and overdrive - is not called into play because the parameters are outside mapped criteria (grade logic comes into play during periods of high engine load or high manifold vacuum).
As a result, hunting - albeit barely perceptible - occurs. This essentially is the repeated and prolonged (for softness!) disengagement and re-engagement of the TCC. Because of the large differences in speeds of the 2 halves of the torque converter prior to re-engagement wear is more pronounced in 6 cyls. It is nonetheless present in 4 cyl models.
My advice therefore is this. Unless you are taking long trips use D3. I use long as a relative term referring only to traffic that allows cruise under lock up to stay steady with only very light accelerative changes. I know the engine noise may sound more pronounced, and gas mileage may go down (but only a smidgeon) the TCC criteria for engagement is more positive and clutch friendly.
Oh, and by the way, depending on driving style, and if yours isn't too hard, wear issues typically don't start until around 40k miles and I recommend (seeing as I practice it myself) ATF oil change every 3rd engine oil change. It may be expensive, but so is the time and inconvenience of having to get you trans replaced.
Keep in mind that the affected clutch/clutches depends on how hard acceleration is. Repeated 4-5, 3-4 or even the infamous stop-and-go traffic 2-3 shifts (which are murder on any trans in any case) will affect these clutches, the amount of material in the ATF, and subsequent pressure anomalies which may then turn around and affect clutch application. Talk about vicious cycles!
Also, let me make sure that you understand that torque converter lockup occurs when mapping dictates that engine load is below a certain threshold. Since there is still a percentage of 'slip' (I forget what the correct terminology is in hydraulic couplers), engine rpm will be higher than optimum for the engine load and vehicle speed.
At this juncture, the TCC provides a positive lock between the crankshaft and the trannsmissions input shaft. This allows for a reduction in engine speed while still leaving the engine enough power to maintain the vehicle's speed. Acceleration essentially puts more of a load on the engine and once the load exceeds the threshold of TCC engagement, the clutch will disengage. We're only talking about a couple of hundred revs per minute and so the shunt may not be perceptible.
The damage really doesn't occur during disengagement but during re-engagement where re-application may be phased so as to be virtually transparent. In your day-to-day commute, you may not feel any of this going on but a glance at the tach whilst you accelerate may reveal the rpm elevation.
Now, you speak of mpg in the 50's!!! I wish I were that lucky. I can only assume that it could cause the repetitive clutch function I spoke of if you drive in D4. Those of us with heavy feet tend to delay TCC application in our transmissions until we hit the open road...sorry...the empty open road which here in MD (at least where I live) is not often. - END.
Is the following another cause of failure and problems with the 5 Speed Automatics from late 2002 onwards?
If you look in your Honda car manual it will tell you that the transmission oil only needs to be changed at 120,000kms. That's right, read it again. But wait, it gets worse, Honda does not even mention the serviceable transmission filter and if pressed some dealers claims that it does not need replacing and lasts the life of the car. This filter is a standard run of the mill small oil filter with an inbuilt bypass valve.
When Honda designed this filter they incorrectly assumed (again) that years of previous AT problems had been solved. This is why they did not identify this filter as a serviceable item, believing that if the filter had enough material to block then the transmission likely had bigger problems to worry about and would soon fail in any case. Not true of course, some bright spark forgot about fine metallic paste and the amount generated in this AT and normally generated in most transmissions. It often coats the outside of this filter and over the years hardens or thickens enough to reduce flow rate.
In the US, recommended oil change interval is up to 120,000 miles - no filter change and less than half the old fluid changed.
Dealers continue to deny this run of the mill small oil filter never clogs, reduces flow or needs changing when used in a transmission that has higher than normal wear and a few design defects that can cause increased amounts of debris to flow through the transmission. Oh! of course! The power of dreams.
A report asking Transmission experts this question. "How often should you replace transmission oil?" The answer was less than 30,000kms in normal usage. In AU, Honda at least recommends changing the transmission oil at 120,000kms and 60,000kms in severe driving conditions. It should be 30,000Kms in severe conditions and 60,000 in normal conditions - but I would halve that again.
Severe driving conditions include stop start traffic which is an absolute killer on Honda transmissions. When was the last time your dealer asked you if you drive a lot in stop start traffic?
Stable bulk oil running temperature is a must. If the temperature rises on uphill or generally hilly running or in headwinds then the transmission oil cooling system needs to be boosted. Bulk oil temperatures less than 110°C to 120°C should be targeted. Above 120°C, there is a real impact on oil oxidation [degradation due to heat] and above 140°C there is a doubling of the rate of oxidation for every 10 degree rise in temperature. So the message here is get the oil temperature stable and keep it below 120 degrees. In a Honda 4AT or 5AT 80°C to 90°C would be a better value to aim for.
Talking about oil temperatures, look inside the transmission at some of the working areas there are much higher temperatures generated.
In the clutch pack, the friction plates that make up the clutch are designed to operate within a defined temperature range, usually between 300° and 400°. These clutches are oil flooded and the transmission fluid is used to dissipate the heat generated and therefore control the temperature of the clutch operation, so the transmission fluid has to withstand temperatures much higher than you see in the transmission sump. Elsewhere in the transmission the oil is undergoing much higher temperatures for example as gear teeth contact one another [momentary 600°C], in the torque converter and differential.
The temperature at which mineral oil begins to oxidise is about 140°C. Under the extreme pressures encountered during gear tooth contact synthetic oil has a higher viscosity than mineral oil. The synthetic has a higher pressure-viscosity coefficient. What this means is the synthetics viscosity rises much faster under the high pressure of approaching metal contact this providing a thicker cushion of lubricating oil. It is this property that gives rise to the claim that the synthetics run cooler than mineral oil.
Synthetics are simply able to keep the metal parts separated for longer thus reducing the time for friction induced heat build-up. With the appropriately calibrated temperature gauge you can see up to 10 degrees difference in transmission bulk oil temperatures. This is the result of the gear set being some 50° cooler in operation on the synthetic.
So considering these differences, there is a real incentive to use synthetic transmission fluids as they are significantly more durable than mineral oils and in turn impart better durability to the transmission. Redline D4 is ideal replacement but priced like liquid gold in some countries and because of mass hysteria on forums, I will not recommend any ATF - you have to decide for yourself - Read the link.
Now when you consider the following:
1. Honda has multiple known problems with all their automatic transmissions since 1996.
2. The transmission design causes high clutch wear and excessive heat build-up in these areas.
3. The recommended transmission oil breaks down rapidly under heat.
4. Hondas recommended change interval is from 120,000km to over 200,000km.
5. Honda changes less than half the old fluid at the recommended change interval.
6. Honda never changes the external filter or dealers will deny that it even has a serviceable filter.
7. In earlier models the weak differential wearing down caused clogging in the transmission which led to numerous failures.
You have to ask yourself what is going on at Honda "Perhaps one too many Honda dreams" If any transmission ever built needs regular oil changes and the occasional filter replacement surely it's this transmission.
Some history, problems and causes.
Honda Motor Co. widened a recall of vehicles in the U.S. and Canada and other locations to 1.14 million units, among its largest, covering Accord and Acura cars that have the same transmission fault that triggered a light-truck recall this year.
The problem results from insufficient lubrication of a transmission shaft that can overheat, potentially damaging gear teeth or causing the gears to break, Honda said in a statement. In rare instances, this condition may lead to gear breakage and possible locking of the vehicle's transmission, creating a potential safety hazard.
Date: 03/08/2004
Supplier Name: Honda Australia Pty Ltd
Product Make: Honda
Product Model: Odessey EXV (V6) variant Accord V6 & V6L variants
Model Years From: 2000-2004
Consequences: Fractured components could lock the transmission possibly causing an accident. Campaign Number: 5CS
Just because you don't read about it on popular Australian forums does not mean that there is not a problem. There are numerous posts in Australia from frustrated owners who vow to never buy a Honda again. The stone-wall arrogant response from Honda Australia is usually the last straw.
If you have a design fault and you refuse to cover any failure outside the warranty period then at least offer a replacement transmission at cost price to the consumer instead of the greedy dealer mark-up price. This is not a plastic clip or disposable part, this is a huge unwarranted expense to the consumer because of Hondas ten year run of problems in these transmissions.
We don't sell the same volume of vehicles as America therefore we don't have the same volume of failures. It has been suggested that overseas outlets for Honda do not seem to be affected with SOME of the transmission problems of the American model. There are quite a few notifications to dealers that indicate certain assembly groups and build locations were, shall we say, a little shabby, and we may have been spared this extra line of faults, however design flaws are present in all locations.
What does not change is the fact that the design of the transmission and implementation of the clutch engagements logic is flawed.
We had the same recall in Australia for insufficient internal lubrication and cooling of the 2nd gear set in the five speed autos. We also have premature failure of transmissions because of a problem causing rapid wear of the clutch packs.
At the time of writing I see many, if not most of the Gen-7 Australian models, are only now reaching the mileage where these design failures start to occur. Do a search for the earlier models in Australia (1997- 2002) and you will find numerous complaints about automatic transmission failures. A substantial number of these cars have under 60,000km and most under 100,000km (62,000 miles) on the clock.
I find the attitude of some of the newer drivers (licensed less than 10 years) to the expected life of a motor vehicle quite ignorant. They have been bought up in a disposable society and believe that if a car has 100,000km on the clock (62,000 miles) that it is long in the tooth and ready to be scrapped. This same group think that if a vehicle is out of warranty that any inherent expensive design faults are not the responsibility of the maker. So if you travel 15,000km in four years and the transmission fails you should pay the $5,000 to $9,000 bill and quote - "Get over it".
It was only a few years ago that a car was considered "just run in" at 100,000km. I have owned three Australian made cars, two Nissan 260z's and a few American Big block fords, all bought with around 120,000km. They ran like new and needed no major service until over 200,000km. What caused the goal posts to be shifted so far for this current generation's attitude on quality and longevity?
If you expect less, then you can bet that politicians, car makers and dealers will give you just that - and charge you more for it. This information by Junior at http://www.vtec.net/ This is one of the best descriptions of the Auto that I have read anywhere.
Fundamentally for those who do not know, Honda's transmissions (and engines for that matter) are closely related to the race motors they are derived from. Being race-bred this technology spills over into the marketplace where everyone from your average Jane to Joe Rocket can sample and love or lump it. That said; let me formally introduce you to Honda's AT's. They are hydraulically actuated manual transmissions! What does this mean?
In a synchromesh manual transmissions (which is what cars marketed today are equipped with) all you ratios are in constant mesh fixed on one shaft while freewheeling on the other. Gear selection is accomplished by locking the freewheeling gear of the desired ratio to the shaft it's spinning on and voila! Your output is served. To make the transition between ratios smoother (as the different ratio gears are obviously turning at different speeds for a given shaft speed) clutch-like devices, known as "syncros" accel &/or decel gears in adjacent ratio pairs before the locks (dog clutches) engage.
Compared to your conventional epicyclical/planetary gear set automatic transmission, ratio selection is far easier, selection more positive and transmission design less complex for ratio addition. In view of this (and the fact that this conclusion had already been arrived at in racing circles, Honda devised and implemented a means of automating gear selection of their manual transmissions instead of lamely following convention.
Their efforts yielded the hydraulically actuated manual transmission found in all their AT equipped vehicles. "How did they achieve automation?" you may ask. Simple, by replacing the brass syncros with wet clutches, all they had to worry about was the ratio itself because clutch pack actuation was already a mastered technology.
The quirk to this transmission was that it had very positive shifts a consequence of wet clutches. Considered more of a boon than a nuisance to race teams, commuters found the shift quality rather alienating, especially since their previous exposure to AT's was limited to the forever-slipping-into-this-ratio-or-that conventional AT.
So the AHM charged to the rescue with soft shifting (read: longer slipping pre-engagement) transmissions. Of course slipping is not good for any clutch and a wet clutch is not excluded. So in '96.5, Honda introduced phased clutch engagement. This allowed for partial engagement of your 'to' gear before your 'from' gear was fully disengaged. This allowed for dramatically smoother shifts than previous models.
The ugly side to this advance was not to reel its ugly head for a couple of years. In late '97. DTC P0740- torque converter circuit failure- was discovered lurking somewhere in between the super-gizmo-wizardry of the PCM and the technologically advanced transmission.
Now early investigation found internal leaks &/or clogged valves to be the culprits. OK. We thought. But the shift quality still wasn't smooth enough. But before I get to what engineer's at AHM decided to do, let me ask you all a question.
How many of you have ever wondered why Honda has always (not now in the advent of flattering emulation by other marques) had 2 drive selections: D3 and D4? Hold that thought as we return to Honda's tranny refinery.
Realizing that pressure modulation was the key to shift shock reduction and that clutches would only stand for so much abuse, Honda looked to a formerly overlooked resource for addition shock dampening: the torque converter clutch. Formerly only used to positively lock the crank to the input shaft, Honda decided to phase its engagement in further efforts to make the AT's operation transparent. It worked for a while. But while existing problems brewed, a whole new batch was thrown in. 740's were jumping all so acrobatically out of the wood work and the more powerful power-trains fell first but their less endowed siblings were soon to follow suit.
While driving, the softer shifts were aggressively wearing away clutch material sometimes in particles that were trapped in screens and filters other times in smaller ones that made it through these lines of defence.
In the former situation, the internal filters (which by the way, are not serviceable) were clogged. This led to pressure loss, which exacerbated the transition duty of the clutches affected, essentially fuelling the vicious cycle's inferno of destruction. In the latter case, accumulation of deposits could occur in the fine passages of the valve body, in/on valve seats etc. Essentially depositing shit where it don't belong.
Now add to this the fact that you average commuter drives in D4 at speeds that equate to the threshold of TCC engagement, the mapped criteria of engagement coupled with the advanced partial engagement modes of the TCC you have a recipe for ATF & Clutch stew. That's an artery clogger if I ever saw one! (No pun intended!).
In so much as these transmission failures seemed to come out of the woodwork all at once, it was actually the accumulation of un-addressed undesirable operational consequences that all came to a head.
Now the newer 5-speed transmissions have the ignominy of having a third working geared shaft. Unfortunately, prolonged torture testing for reliability of this set wasn't long enough and internal lubrication and cooling weren't discovered until many owned vehicles with these ill-fated trannies in them. The fix: add point of correction cooling + lubrication by plumbing ATF to the problem. Hence the latest transmission recall in a seemingly endless stream of tranny woes. I must say one thing at this juncture. Redesign has rid the 5-spd transmissions of their heating problem.
Here's the deal on D4 and D3 gear selection that the driver has to make. Aside from the engagement (or not) of 4th gear or 5th gear (depending on the trans), the PCM is also mapped to lock up the torque converter at different engine loads and vehicle speeds.
The problem here is that this information is not relayed in any way shape or form to Honda owners. So here it is in terms you can use.
At the speeds, gear selection, and (I'm guessing here) average traffic conditions, you may feel a barely perceptible "shift" when you accelerate (for whatever traffic mandated reason) from your cruise speed. 'Grade logic', one of several fuzzy logics (designed to fine tune slight adjustable operating parameters to the driver's average driving habit(s)) is designed to prevent gear hunting - in this case between fourth (or fifth gear) and overdrive - is not called into play because the parameters are outside mapped criteria (grade logic comes into play during periods of high engine load or high manifold vacuum).
As a result, hunting - albeit barely perceptible - occurs. This essentially is the repeated and prolonged (for softness!) disengagement and re-engagement of the TCC. Because of the large differences in speeds of the 2 halves of the torque converter prior to re-engagement wear is more pronounced in 6 cyls. It is nonetheless present in 4 cyl models.
My advice therefore is this. Unless you are taking long trips use D3. I use long as a relative term referring only to traffic that allows cruise under lock up to stay steady with only very light accelerative changes. I know the engine noise may sound more pronounced, and gas mileage may go down (but only a smidgeon) the TCC criteria for engagement is more positive and clutch friendly.
Oh, and by the way, depending on driving style, and if yours isn't too hard, wear issues typically don't start until around 40k miles and I recommend (seeing as I practice it myself) ATF oil change every 3rd engine oil change. It may be expensive, but so is the time and inconvenience of having to get you trans replaced.
Keep in mind that the affected clutch/clutches depends on how hard acceleration is. Repeated 4-5, 3-4 or even the infamous stop-and-go traffic 2-3 shifts (which are murder on any trans in any case) will affect these clutches, the amount of material in the ATF, and subsequent pressure anomalies which may then turn around and affect clutch application. Talk about vicious cycles!
Also, let me make sure that you understand that torque converter lockup occurs when mapping dictates that engine load is below a certain threshold. Since there is still a percentage of 'slip' (I forget what the correct terminology is in hydraulic couplers), engine rpm will be higher than optimum for the engine load and vehicle speed.
At this juncture, the TCC provides a positive lock between the crankshaft and the trannsmissions input shaft. This allows for a reduction in engine speed while still leaving the engine enough power to maintain the vehicle's speed. Acceleration essentially puts more of a load on the engine and once the load exceeds the threshold of TCC engagement, the clutch will disengage. We're only talking about a couple of hundred revs per minute and so the shunt may not be perceptible.
The damage really doesn't occur during disengagement but during re-engagement where re-application may be phased so as to be virtually transparent. In your day-to-day commute, you may not feel any of this going on but a glance at the tach whilst you accelerate may reveal the rpm elevation.
Now, you speak of mpg in the 50's!!! I wish I were that lucky. I can only assume that it could cause the repetitive clutch function I spoke of if you drive in D4. Those of us with heavy feet tend to delay TCC application in our transmissions until we hit the open road...sorry...the empty open road which here in MD (at least where I live) is not often. - END.
Is the following another cause of failure and problems with the 5 Speed Automatics from late 2002 onwards?
If you look in your Honda car manual it will tell you that the transmission oil only needs to be changed at 120,000kms. That's right, read it again. But wait, it gets worse, Honda does not even mention the serviceable transmission filter and if pressed some dealers claims that it does not need replacing and lasts the life of the car. This filter is a standard run of the mill small oil filter with an inbuilt bypass valve.
When Honda designed this filter they incorrectly assumed (again) that years of previous AT problems had been solved. This is why they did not identify this filter as a serviceable item, believing that if the filter had enough material to block then the transmission likely had bigger problems to worry about and would soon fail in any case. Not true of course, some bright spark forgot about fine metallic paste and the amount generated in this AT and normally generated in most transmissions. It often coats the outside of this filter and over the years hardens or thickens enough to reduce flow rate.
In the US, recommended oil change interval is up to 120,000 miles - no filter change and less than half the old fluid changed.
Dealers continue to deny this run of the mill small oil filter never clogs, reduces flow or needs changing when used in a transmission that has higher than normal wear and a few design defects that can cause increased amounts of debris to flow through the transmission. Oh! of course! The power of dreams.
A report asking Transmission experts this question. "How often should you replace transmission oil?" The answer was less than 30,000kms in normal usage. In AU, Honda at least recommends changing the transmission oil at 120,000kms and 60,000kms in severe driving conditions. It should be 30,000Kms in severe conditions and 60,000 in normal conditions - but I would halve that again.
Severe driving conditions include stop start traffic which is an absolute killer on Honda transmissions. When was the last time your dealer asked you if you drive a lot in stop start traffic?
Stable bulk oil running temperature is a must. If the temperature rises on uphill or generally hilly running or in headwinds then the transmission oil cooling system needs to be boosted. Bulk oil temperatures less than 110°C to 120°C should be targeted. Above 120°C, there is a real impact on oil oxidation [degradation due to heat] and above 140°C there is a doubling of the rate of oxidation for every 10 degree rise in temperature. So the message here is get the oil temperature stable and keep it below 120 degrees. In a Honda 4AT or 5AT 80°C to 90°C would be a better value to aim for.
Talking about oil temperatures, look inside the transmission at some of the working areas there are much higher temperatures generated.
In the clutch pack, the friction plates that make up the clutch are designed to operate within a defined temperature range, usually between 300° and 400°. These clutches are oil flooded and the transmission fluid is used to dissipate the heat generated and therefore control the temperature of the clutch operation, so the transmission fluid has to withstand temperatures much higher than you see in the transmission sump. Elsewhere in the transmission the oil is undergoing much higher temperatures for example as gear teeth contact one another [momentary 600°C], in the torque converter and differential.
The temperature at which mineral oil begins to oxidise is about 140°C. Under the extreme pressures encountered during gear tooth contact synthetic oil has a higher viscosity than mineral oil. The synthetic has a higher pressure-viscosity coefficient. What this means is the synthetics viscosity rises much faster under the high pressure of approaching metal contact this providing a thicker cushion of lubricating oil. It is this property that gives rise to the claim that the synthetics run cooler than mineral oil.
Synthetics are simply able to keep the metal parts separated for longer thus reducing the time for friction induced heat build-up. With the appropriately calibrated temperature gauge you can see up to 10 degrees difference in transmission bulk oil temperatures. This is the result of the gear set being some 50° cooler in operation on the synthetic.
So considering these differences, there is a real incentive to use synthetic transmission fluids as they are significantly more durable than mineral oils and in turn impart better durability to the transmission. Redline D4 is ideal replacement but priced like liquid gold in some countries and because of mass hysteria on forums, I will not recommend any ATF - you have to decide for yourself - Read the link.
Now when you consider the following:
1. Honda has multiple known problems with all their automatic transmissions since 1996.
2. The transmission design causes high clutch wear and excessive heat build-up in these areas.
3. The recommended transmission oil breaks down rapidly under heat.
4. Hondas recommended change interval is from 120,000km to over 200,000km.
5. Honda changes less than half the old fluid at the recommended change interval.
6. Honda never changes the external filter or dealers will deny that it even has a serviceable filter.
7. In earlier models the weak differential wearing down caused clogging in the transmission which led to numerous failures.
You have to ask yourself what is going on at Honda "Perhaps one too many Honda dreams" If any transmission ever built needs regular oil changes and the occasional filter replacement surely it's this transmission.
