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!

 

[BrianPetersen]

A certain European manufacturer that I'm familiar with, does not specify any fluid change interval for either their manual or traditional automatic gearboxes. (the new dual-clutch designs are a different matter, for some reason, those have a fluid change interval).

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.

 

[TrackRat]

Thanks for the additional commentary folks.

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.

 

[izzmus]

Specific to the GM transmission: I was under the impression that the final two numbers in the new Hydramatic naming system were a torque rating.

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.

 

[TrackRat]

That may explain the relatively high clutch wear?