Auto transmission loses reverse when warm...

[jqjones3]

Hi there, i just purchased a 92 325is and found out after the sale that after the car warms up it looses reverse. It has 230,000 miles on it and im quite sure that the transmission fluid has not been changed. Do you think that will solve the problem if i change it and add some lucus transmission fix to it, or is my tranny shot?

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This post was auto-generated based upon a question asked on our tech article page here: Pelican Technical Article: BMW Automatic Transmission Fluid Change

[Wayne 962]

I haven't heard of this specific problem before, but yes, I do not think that changing your fluid and adding some long-life additives will hurt. It's worth a try, it only takes a portion of an afternoon for the change.

- Wayne

[bostogrun]

The Lucas may work. The realtionship between warm up and loss of functionality is most likely caused by internal wear on the actuators or servos that control the bands or clutches that hold the planterary gears to produce reverse. Reverse is produced by driving the common sun gear and rear planetary gear is held stationary. I think your problem is a worn servo that holds low and reverse clutches. It could also be a problem with the valve that supplies hydraulic pressure to that circuit. That problem is better served with a product like Sea Foam Trans Tune that is actually a solvent that can dissolve build up in the worm like passageways in the valve body. If you want to take a risk of $50 to try to save this old tranny, no gurantees here. Try this: Drain out a quart of the fluid from the drain on the bottom of the pan. Pump in a pint of Seafoam Trans Tune. Drive the car for a couple of days. Pick up a filter kit, two bottles of Lucas Transfix, two quarts of Dexron 3, do not use synthetic!!! it's to slippery. Drop the pan as per Wayne's tutorial, with the pan off the car, put the two bottles of Lucas Transfix into the pan and reinstall it with new gasket and filter. Then finish off the fill following the procedure to get the right ammount in.

I have actually done this before and I got another 25k out of a tranny. If it doesn't work you are going to have to replace the tranny any how so what do you have to loose. In my opinion.


Put the Lucas n the pan while it's off the car you will never get it in the filler hole with a hand pump.