It has been mentioned before in many of the Chapter newsletters, but can stand another repeat. If you find the transmission grinding on shifts from first to second, do not get the thing torn down right away. Drain and top up (almost two quarts) with a name-brand straight 30W oil (not 10W-30). You may have the wrong oil in there to start with. Many shops carry SAE 90, not SAE 80 as specified. Your owners manual says you can use a motor oil, so you are not violating any warranty by doing so. If the noise goes away, the oil was causing the problem.
Use 30W in the summer and 20W in the winter. With 20W it won't crunch even at 50° F; I know! The difference is explained this way: The petroleum base for transmission and motor oils are identical. The motor oil has additional additives for engine use which will not harm the transmission. Some transmission oils sold in this country are not as closely controlled as the ones in Europe. Therefore, it averages as an SAE 80, but can actually range from SAE 70 to 90. The higher viscosity (SAE 90) oil has more "sticktion" and allows metal parts to stick together. The crunch you hear is the result of a moving baulk ring meshing with a stationary (suppose to be freely moving) syncro. I have seen cars with such an extreme problem that you could park the car on a slope overnight and in the morning, with the brake off and the clutch depressed, the car would not move! When I pushed the car I heard a *SNAP* and the car started to roll. Now thats sticktion!
Author: Bence Boelskevy
For the love of classic BMW 2002s everywhere. Copyright 2012 02Restoration.com. All rights reserved.
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