Bimmerfest - BMW Forums - View Single Post - E34 535i transmission problems
View Single Post
Old 10-06-2012, 06:54 AM
snowsled7 snowsled7 is offline
The Ornery Old Man
Location: SW Mountains
Join Date: Mar 2012
Posts: 980
Mein Auto: GTI
Originally Posted by robertobaggio20 View Post
If you recently had your fluid changed, and then you began experiencing these problems, you have encountered an unfortunately common situation.

The old fluid would have been much thicker than the new one. This actually worked to reduce or prevent slippage between worn clutches. The tradeoff is the your transmission is less efficient due to thicker fluid, so your mpg will fall. Further, wear will be accelerated due to the old oil.
I have no idea how you came up with this, and it certainly isn't common. How do you figure the old fluid was thicker when you don't know which fluids have been used in the trans? ATF is pretty consistent stuff, changing it should never produce ill effects, that is no more than internet legend.

When you changed to new oil, it was too thin visavis the worn transmission, to prevent slippage.
Actually, what is wrong is that the trans pump can no longer maintain enough pressure for the trans to function properly. THIS is pretty common on older auto transmissions.

The solution will be to either switch back to the old oil if you kept it away, or change the oil to a thicker blend. Alternatively you could try one of those friction modifiers that they sell off the shelf which is supposed to "reduce slippage". Since you have a dipstick, perhaps you'd like to try that by pouring it in through the dipstick to see if it helps.

The next best bet would be to try changing the oil to a clean oil but which is thicker than what is recommended for your transmission.

There is an outside chance that you actually used thinner fluid than what is recommended for your tranny and your tranny is actually ok. Very long shot but do rule that out if possible.

Download the soft copy of the E34 Bentley manual for details about transmissions and recommended oils.
This trans problem has nothing to do with the thickness of the ATF. I am not sure where you are finding thicker and thinner versions of ATF???

You'll be able to have a good discussion about these elements with a seasoned indie mechanic.

In any case, your transmission is probably not in good shape. It is unlikely that you'll be able to sell your car without taking a huge haircut. Considering the size of that haircut, you might elect to keep it and try to salvage the transmission in the ways I've described above.

Unless, of course, its really no longer worth your while.
The trans needs a rebuild. For about the same money, and probably less you could swap in a five speed and be done with it.
Current ride... '13 GTI Wolfsburg
BMW's from my past...
'92 535i/5 '89 325ix/5
'98 750iL '86 325(e)/5
'95 740iL '84 318i/5
Reply With Quote