Lifetime Trans/Diff Lubes ?
Lifetime Trans/Diff Lubes ?
(OP)
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!
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!





RE: Lifetime Trans/Diff Lubes ?
RE: Lifetime Trans/Diff Lubes ?
One of the complaints that I've read about was with BMW auto trans issues around 50K miles.
RE: Lifetime Trans/Diff Lubes ?
"Lifetime" means "projected lifespan" as I see it and that's pretty open ended.
Rod
RE: Lifetime Trans/Diff Lubes ?
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.
RE: Lifetime Trans/Diff Lubes ?
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.
RE: Lifetime Trans/Diff 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.
RE: Lifetime Trans/Diff Lubes ?
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
RE: Lifetime Trans/Diff Lubes ?
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.
RE: Lifetime Trans/Diff Lubes ?
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
RE: Lifetime Trans/Diff Lubes ?
RE: Lifetime Trans/Diff Lubes ?
Regards
Pat
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RE: Lifetime Trans/Diff Lubes ?
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.
RE: Lifetime Trans/Diff Lubes ?
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):
h
Cheers,
Benta.
RE: Lifetime Trans/Diff Lubes ?
RE: Lifetime Trans/Diff Lubes ?
RE: Lifetime Trans/Diff Lubes ?
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.
RE: Lifetime Trans/Diff Lubes ?
RE: Lifetime Trans/Diff Lubes ?
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.
RE: Lifetime Trans/Diff Lubes ?
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
RE: Lifetime Trans/Diff Lubes ?
With the 5 speed manual transmissions, usually what happens is that a tiny amount of fluid slowly weeps out past the shaft seals (and/or the drain plug), causing the oil level to ever so gradually go down. Eventually that causes 5th gear to become high and dry, no longer dipping into the oil bath. Eventually *that* causes the plastic cage that contains the rollers inside the 5th gear adjacent to the synchro to run dry, then run hot, then melt, then mayhem ensues. If you at least check the fluid level every year or two and make sure there is enough in there, even if you don't change it, this never happens.
With the automatics, the clutch packs inevitably wear over time, and the transmission eventually goes boom, but I don't think anyone has established whether changing the fluid actually helps. I've seen the fluid in those after about 80,000 km, and I sure wouldn't want that nasty stuff inside any transmission that belonged to ME.
RE: Lifetime Trans/Diff Lubes ?
The required service info. that I have seen always states to periodically check the fluid levels and top up as required.
Clutch wear issues in an auto trans certainly vary by make/model and application. Most service recommendation for pass car use is for "normal use" which can be a grey area. From what I've read so far it looks like the lube is not a real issue, it's other factors that might be an issue depending on the application.
RE: Lifetime Trans/Diff Lubes ?
If that is, indeed, the case, then the automatic being installed behind BMW engines 3 liters and up is something that GM itself would only use behind a relatively weak four-cylinder. I am unsure if any amount of fluid changes would stave off the inevitable.
RE: Lifetime Trans/Diff Lubes ?