Lifetime Trans/Diff Lubes ?

[TrackRat]

I did a search and didn't really find much so I'm throwing this out for discussion. I'm specifically looking for info. from lubrication durability test folks if possible. I don't want this thread to turn into an anecdotal discussion on my favorite lubes... :>)

My question is does anyone on here have expertise on the viablity of lifetime synthetic lubes in trans and diff pass car applications? The point being that certain units have had failures or operational issues that some owners believe are the result of using a "lifetime oil" vs. changing these lubes say at 50K miles.

Some owners view the lifetime oils as a mfg. cost savings issue but in reality owners are the ones who pay for most maintenance after 50K miles so this doesn't seem to have a lot of merit. I'm hoping someone has first hand durability test data that states for a given trans/diff that the required synthetic oil is in fact a lifetime fill or no it really should be changed at XX miles or that an annual UOA should be performed every xx miles or whatever.

I'm aware of BITOG and there is some good info. there but also a lot of nonsense and baseless claims/beliefs. Hard test data works better for me. <LOL>

So please speak up if you have tech data to support or refute the viability of lifetime oils for a given pass car trans/diff application.

Thanks!

 

[CoryPad]

The lubricant can last the lifetime of a typical vehicle (100,000 miles +). There are many stipulations: avoid overheating, provide proper filtration/segregation of abrasive particles, exclude water, etc. If you do these things, the fluid is suitable for use for extended times. Our dynamometer testing of automatic transmission fluids and gear oils (and customer experiences) show that "lifetime oils" are viable.

 

[TrackRat]

Thanks CoryPad. I appreciate the info. I have faith in science and engineering but sometimes reality is different than the test lab results. I'm glad to hear that your test results concur with owner experiences.

One of the complaints that I've read about was with BMW auto trans issues around 50K miles.

 

[evelrod]

It's terribly difficult to relate to some of the so called 'lifetime' lubricants. An anectdote is the best I can do...Our old '77 Dodge 3/4T Camper Special went a bit over 380,000 miles on the OEM lube in the rear axle. Repacked the wheel bearings a time or two, but never changed the gear oil. Last I saw the truck, it was just fine and headed toward 400k...

"Lifetime" means "projected lifespan" as I see it and that's pretty open ended.

Rod

 

[TrackRat]

I understand evelrod. 380K is a long time!

I don't personally expect a trans/diff lube to last beyond a 100K miles but I was curious how the actual lab/field testing looked as some auto enthusiasts believe the oil lifetime rating is cost motivated and that the oil can't function properly for that long of period without enough deterioration to cause mechanical issues.

 

[Tmoose]

MOPAR in the mid/late 60s ( 5year, 50,000 mile warrantee, not that I think manufacturers can target failure just beyond warrantee expiration )said the auto trans and diff original factory fill oils did not need to be changed, unless cop or taxi service, or a Hemi, or any of a few other extreme service definitions. And once the oil was changed, it was to be changed on a schedule.

AntiWear and EP additives are sacrificial, so if service is tough enough to bring them into play, their "life" (quantity) can define the lube's life.

 

[TrackRat]

I worked in a Chrysler dealership in the late seventies and about the only vehicles we ever needed to rebuild trannys on were taxis. Even the police vehicles had no issues with trannys though they tended to go thru a few 440 engines on high speed pursuits when the oil had gotten low... We performed normal tranny oil/filter service and never saw any issues before 100K and that was without synthetic lubes.

I don't recall ever changing diff lube unless we rebuilt a diff. so I guess they were easy on the lube as we rarely had failures. We would change the fluid on Sure-Grips however to be safe.

 

[tbuelna]

TrackRat,

For an application like a production automotive final drive, it's my professional opinion that a truly "lifetime" lubricant is probably not realistic. With a simple splash-type, unfiltered lube system like in most auto rear ends, the biggest culprit is always moisture, and not debris accumulation or breakdown of the lubricant itself. The repetitive heating and cooling cycles the lube oil undergoes over many years will cause humidity in the enclosed airspace to condense out and accumulate in the oil. As the car sits idle, wherever this water touches a steel gear or bearing surface it will quickly cause corrosion pitting. And it's this surface corrosion pitting that initiates spalling failures in gear tooth surfaces and bearing races.

It's fairly easy to formulate a gear oil that will last the full service life of typical auto final drive. But unless you can keep it free of moisture somehow, it won't be effective.

Hope that helps.
Terry

 

[TrackRat]

Thanks for the feedback Terry.

Wouldn't diff and car makers take the moisture accumulation issue into consideration when durability testing and defining a specific lube for the diff? I realize the quantity of moisture can vary significantly in different environments but I would expect the tribologist/lubrication engineers involved to be confirming suitability of the lube for the obvious accumulation of condensation over time?

Most OCIs that I have seen are for "normal service" and in severe duty apps OCIs are much shorter.

 

[tbuelna]

TrackRat,

Engine lube systems have the same problem. And engine oils typically have an emulsifier additive, which helps to keep the moisture somewhat suspended within the oil. But engine oils get changed frequently compared to rear end lubes.

I design aircraft transmissions for a living, and these gearboxes have the same issue with accumulated moisture in the lubricant causing corrosion of gears and bearings. To prevent this moisture accumulation, it is standard practice to use a sealed gearbox housing with a desiccant-type breather filtering the incoming air. Of course, such an approach would not be acceptable to the very cost-sensitive automotive industry.

Regards,
Terry

 

[TrackRat]

So Terry are you saying you don't really believe the pass car lifetime trans/diff fluids are legit in that they should last until say 100K without component failure issues? I would think the vendor component and car mfgs. actually conduct durability testing of this before making a "lifetime" fill declaration? After 50K in most cases it's customer pay so I would think if a lube change was required they would tell customers just to change it at 50K on their dime?

 

[patprimmer]

Lifetime no service is becoming a major marketing push from what I see, so it is something they want to say and while they may not lie, they may push the truth as far as possible, hence all the limitations.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

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for site rules

 

[TrackRat]

Thanks Pat - that's what I'm trying to determine based on actual durability testing. It sounds like from what Cory posted that there actual testing and customer experience on auto trans has been good, which is of interest as one of the failure issues I ready about was in BMW auto trans.

I have an engineering friend that works at a major Euro diff supplier who I asked about lifetime lubes in their units. He said that in additional to lab and field testing they actual have a fleet of vehicles that are raced every few weeks in Europe in a spec series and they have gone six years on the OE fill without any failures.

I understand that the lube itself may not fail and as Terry mentioned a buildup of water can cause rusting, spalling and failure so that is why I was looking for actual durability testing experience or even known field failure issues due to lifetime lubes or operation.

I'm not trying to prove or disprove the claims per se, just looking for real world testing and operational data.

 

[benta]

This has been a major theme in Germany, on television and in car magazines.
Specifically it revolved around the 5L40E transmission from GM, which is used (among others) by BMW.
A large number of owners had experienced transmission failures after 110,000...200,000 km, with costly repairs (5 kEuro).

Interviews with a number of gearbox rebuilders all gave the same response:
"Lifetime no service is B.S." They unanimously recommended oil and filter change at around 80,000 km (100...200 Euro).
Impressive pictures of black oil (clutch residue) and partially blocked filters were to be seen.
Link to a video here (sorry, it's in German):

http://www.vox.de/video/index/anzei...e_id/24272/playlist/71/headline/BMW-Getriebe/

Cheers,

Benta.

 

[benta]

By the way, if you search "5L40E" you'll get lots of hits with frustrated owners.

 

[TrackRat]

In my experience if the trans filter is partially plugged at 50K it sounds more like clutch wear than a lube issue? Most trans oil/filter changes I've done at 50K the filter only had very minimal debris.

 

[benta]

Not plugged at 80,000 km, this was the recommendation for changing.
The owners with destroyed transmissions all had over 110,000 km on the car.
Yes, it seems to be clutch wear, but only an oil change would flush that.

Benta.

 

[TrackRat]

So it sounds like in the BMW/GM auto trans situation maybe there is some other trans issue, not the lube per se? Maybe they don't have proper clutch materials, torque capacity, cooling, etc. for the application? From what you have described it would appear that changing the oil/filter at 50K may delay the eventual trans failure but clutch wear appears to be the primary issue not the lube?

 

[benta]

Could be, I only have the information above.
By the way, I just realised my link only goes to a generic page, not to the relevant video.
Sorry, but I don't know how to fix it.

Benta.

 

[tbuelna]

TrackRat,

I didn't mean to imply that it is not possible to get very long life from a particular gear lube in a particular gear drive or transmission. And "durability" testing is usually of very little value with regards to gear and bearing life. To understand why "durability" testing of gears and bearings is not of much value, you have to understand how fatigue affects their operating lives.

Gears and rolling element bearings have operating life hours typically expressed by values such as "L10". L10 fatigue life is a statistically derived number that says for any given sample of these bearings operating under the specified conditions, 90% of them will achieve this operating life. Some of them may even last 5 times as long. To get statistically relevant fatigue life data from a durability test, you would need to test a large number of gearbox samples for a very long time. And this would not be practical in any application. That is why statistical fatigue life analysis is used in these situations, and not testing.

With properly designed and manufactured rolling element bearings and gears, the most common failure mode (by far) is bearing race or gear tooth surface spalling due to contact fatigue. Surface pitting due to corrosion accelerates spalling failures by creating stress concentration points where cracks will initiate.

Hope that helps.
Terry