I have a '83 300SD w/ 135K on the motor and excellent condition body. I purchased a year ago for $1K and the tranny recenlty started skipping gears and a couple mercedes guys told me that it was shot and my only options were to purchase one from a dealer. Well, $2-3K wasn't going to happen, so I took the difficult way and put one in from a junk yard. First one was no good. Now on my second replacement, it doesn't upshift properly. I brought the car to a "transmission" guy. He charged me $150, had my car for 3 weeks, stole my sunglasses, and the car is the exact same as when I brought it to him. Does anyone have any advice as to what adjustments I can make on the transmission? Is it possible that the shifter selector rod needs better adjustment? The modulator valve has been replaced. I have noticed that the car can be moved when I have it in Reverse as well as Neutral. I've adjusted the down shift cable and that doesn't seem to have any effect on the tranny performance. Please help!

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I don't know why, but those Germans just can't build a reliable auto trans until a car is well out of warranty. You can bet MB has a good replacement for your car. If faulty auto trans were a safety issue requiring a recall, MB would be out of the car selling business and in the car-repair-for-free business.

Anyway, I think you've proven to yourself that you need to go the $2-3K route. If the modulator valve replacement didn't do anything, your tranny is shot. So are all the ones in junkyards unless you can find a car with a replaced trans. Are/were there any metal filings in the fluid pan?

As one last desperate shot at it, you can check the modulator adjustment. It may need to be increased. Sometimes the shifts will loosen after new parts break in.

 

These transmissions are different. If you don't know what you are doing they make no sense. The modulator is best adjusted using an oil pressure gauge. The cable is adjusted to zero slack, but also no tension. After these are set properly then you can see if you have a rearl problem. The bands my be wearing. There are different size rods to bring the clearances back into specs. There are also many other adjustments which can be made. Not alot in parts but time intensive.