In Reply to: Excellent Brian except # 3 posted by Kirt Koeller on August 31, 2001 at 09:00:17:
Brian is right on the money except on why the neutral rev cause death the reason is that while reving in neutral the increase in pressure causes the fluid to pass the sealing rings and apply the forward clutch NOT GOOD! but most of the rebuilds have addressed that problem by replacing the steel sealing rings with Teflon rings and you don't get the fluid to pass by Teflon. This particular unit has no more problems then ANY other trannys. Try asking a VW automatic owner (4 speed) now THATS a bad unit. For every 1 ZF 4HP22 I do I do 15 VW's so when some people call the ZF's slush boxes I have to laugh they have no idea that the slush box they have is actually a pretty good unit compared to a lot of units out there.
lots of talk about failure in the archives, but here's a summary:
1. make sure fluid has been changed regularly before you change it again, as there have been many reports of changes on neglected transmissions accelerating or causing problems
2. if it has been changed regularly, keep doing it. many people find mobil 1 synthetic or Redline ATF a good alternative to the standard fluid (i use redline)
3. don't rev the car in neutral for extended periods. it sounds odd, but emissions tests that required the car to be revved in neutral were known to send your car's transmissions to the grave - something about fluid not being circulated when the car is in neutral, and clutches being burned out.
there have been other known failures, and some would say excessive failures on the 4hp22 that you have, but also many examples of cars with 250k+ on the original transmissions with no problems. it's probably accurate to say that the auto transmissions on the cars are not known to be quite as solid as the M30 engine, which is extremely rugged when taken care of.
Currently driving '91 535 sport Auto with 182000 miles. Stong car engine wise - head off recently - virtually no wear. Full BMW service history. What I wanted to ask was how strong are the auto boxes? I understand BMW change trans oil every Inspection2. Is there anything to watch for?