The new Audi TT owner's manual doesn't even tell you WHERE the oil drain plug is. And the splash pan w/about 14 screws has to come off to get to the plug...and you better know the difference between the oil drain plug and the trans drain plug. Luckily, you can buy the service manuals on CD for $100.

The Audi is another German car...and their service policy probably is more liberal than the new Porsche service recommendations. Overall, the 928 is not that difficult of a car to work on....if you have really small hands and a box of special tools...and follow the dots carefully.

H2

 

How about newer (2000 on) cars that don't even have a transmission drain plug or dip stick? In the manual they claim the fluid is good for the life of the car. So I guess this "life" is the length of the warranty. I've already seen a fare share of cars in this catagory with failed transmissions. Upon disassemble, the fluid (or whats left of it) was sludge. Most were around 100,000 miles.

 

Those "life" fluid claims scare me. It would be interesting to see what the "industry" considers a car's lifetime to be these days. I'm sure our 928's are all on post-post life support or there hereafter by now.

 

One of my customers was GM transmission in Windsor who make the 4T40E transmission (now the 4T50E I think). They spent a huge amount of energy making sure there was no debris in the transmission. They proved that the dirt that was getting in through dipsticks and filter changes was a huge factor in the life of the transmissions.

The only way sludge would be in there is from abuse (overloading be the most common)

The automatic transmission is actually not that hard on the fluid. All parts are rotational unlike in an engine. and other than frictional forces no heat is generated (combustion)

 

SAAB has done that on manual transmissions for at least 17 years. They have a procedure in the service manual for suctioning oil out in hard use or flooded cars. In normal use, 200,000+miles is not unusual. Their worry is more that people will use the wrong oil or the wrong volume of oil.

My Jeep says the tranny (and maybe transfer case, I forget) is lifetime fill unless you fall into one of their hard use categories (towing, submerged in water, very dusty, extreme temps, and one or two more). They also have different motor oil change intervals in the owner's manual for normal and hard use.

 

Hey, I found it. Recent study, too.

http://www-nrd.nhtsa.dot.gov/pdf/nrd...006/809952.pdf

"The updated analysis shows that a typical passenger car will travel a lifetime mileage of 152,137 miles, while light trucks will travel 179,954 miles. Passenger car lifetime weighted present discount factors at 3 percent, 7 percent and 10 percent are, respectively, 0.8304, 0.6700 and 0.5824; for light trucks with the same discount rates, respectively, 0.8022, 0.6303 and 0.5419."

 

Hi,
I can offer perhaps another perspective on lifetime fluids (auto box/gearbox/diff) based on experience in the Trucking Industry

1 - Suitable synthetic auto transmission fluids such as Castrol's Transmax Z (Dexron 3) do a great job in heavy trucks and in those equipped with retarders. It has Approvals from many manufacturers such as ZF, MB, Voith and etc. Recommended OC points in these very severe applications are around 400000kms - IME this is quite conservative

2 - Gearbox and differential oils (conforming to intended application) are suitable for up to 1 million kms and beyond without significant deterioration. Contamination (water etc) can be an issue in some applications of course. In my case at around 1m kms wear metals such as Iron had reached around 1200ppm and Copper around 120ppm - the limits set by Rockwell, Eaton-Fuller and etc. Recommended OC points are around 400000kms with synthetics and around 100000kms with mineral lubricants - IME these are also conservative figures!

I conducted Used Oil Analysis (UOAs) on my heavy truck's drive lines with both Mobil SHC50, SHC 75w-90, and Castrol's Syndrive50E, Syntrans 75w85(GL4), Syntrax75w-90 and SyntraxE for many years from 1992. Both the Mobil and Castrol products performed about the same in extended use - I never had a lubricant related transmission/diff failure

Rod - As you stated contamination is an issue, even with new components.
During 1989-1992 Eaton Fuller conducted application research on the use of synthetic lubricants in heavy truck drive lines. They found that an initial change from a sulphur based lubricant was needed prior to about 5k kms to prevent the "build up" of EP coatings and to remove assembly and "initial bed in" wear contaminants. Then, the incidence of seal and bearing failures was reduced by an enormous amount throughout the life of the component

In my own experience commencing in 1993 with my own vehicles we determined a zero OC policy (after the initial drain) and we had very low wheel seal and wheel bearing replacements which mirrored Eaton's findings. Much of this can be attributed to the significant reduction in component temperature due to the synthetic lubricant's superior operating characteristics

Some of my "old" (on sold) gearboxes, diffs are still operating with the same heavy components at up to nearly 3m kms. Some of my Detroit engines reached well over 2m kms without major rebuild. The average OC interval with my engines was 90k kms

It was once common to re-race a RoadRanger multi-speed (13-20speed) gearbox at an average around 120000kms

Eaton and other US and Euro truck component Makers now factory fill with synthetic fluids

The ONLY diff failure I ever had was when a Service Provider failed to check and replenish a front diff (tandem drive) over some months - they paid the $A18000 involved for the replacement!

IMHO like with engines - follow what the manufacturer advises unless you use UOAs and etc to determine otherwise

Just another perspective

Regards

 

wow. This thread is producing some really interesting info. Thanks Doug.

 

My brother was a quality control engineer for a turbine company and an aerospace outfit - they lived by the 'bathtub curve'. Most failures occur right away (early in system life) or at the very end of system life. Each time you "fix" the system you start another cycle and subject the system to another "start" cycle and you are in the high failure rate time period. This is what we all call - If it ain't broke, don't fix it. I love the signature of one of our members something like he'll fix it till it is broke. We've all been there - just broke a connector on the XR with arthritic hands.

 

As always Doug, your expert opinion - if opinion is even the right word with all your experience - is greatly appreciated.

I'm glad that even though you're no longer a shark owner (you know it's only temporary!), you still hang out here.

 

Is an English speaker who uses the word "Poseur" to describe a "Poser" a poseur?