My SD is shifting hard. The trany shop replace a couple of small vacuum switches in the engine compartment (and popped me $125 for two 5 dollar valves) they also said to replace the vacuum switch on the trany. I got the correct color switch from a parts house. There was a paper in the box that said "Attention! To prevent gearbox or engine damage the vacuum unit must be adjusted as explained in Workshop Manual before vehicle is driven"

Of course I don't have a Workshop Manual. I cannot see anything to adjust either. Any tips?

Sounds like you are talking about the modulator. There is a black rubber cap that when removed covers a key which alters the pressure given at any vacuum level.

Proper adjustment is done with a pressure gauge hooked to the appropriate port. At a certain rpm with the vacuum removed the pressure should be that which is shown in the manual for your transmission.

The actual working of the vacuum modulator is severely dependent on the proper working and adjusting of the vacuum system. This is probably the problem in 99 out of 100 harsh shifting problems. There is no point in trying any of this without a vacuum gauge and a vacuum schematic.

There are a few reasons why there is value in that 125 dollar switch replacement. But, it seems they didn't finish the job. I could tell you how to do it in a few hours. After a year or two, you could do in a few hours of experimenting what I can do in 15 minutes. How much is it worth??

Sorry Steve, I don't mean to sound cheap. I made a real mistake by going to a little trany shop around the corner. They were only suppose to change the filter and fluids plus eval the trany. The took me for $425 total. The two small valve in a black box on top of the valve cover were charged to me as $125 and when I checked with my MB parts guy he said they are around $5 each. I guess I learn a lesson, if I can't do it myself take it to a MB tech!

I'd love to pay you to help me but I'm in CA and I think you are in GA I think.

Actually I am in Florida.

I didn't mean to infer that you were cheap. I don't know the price of the plastic vacuum microswitches but in a retail situation I'm sure it isn't $5. My point was more directed to the feeling I often get when reading such declarations. I can't tell you how many times a customer has come to me with a problem and declared that we had just done $800 dollars worth of service to his car. Upon checking the facts I find an oil change service, a set of tires and a new stereo.

BTW the worlds two greatest lies to an auto technician start out: It never happened before I ... and Just do the minimum I'm going to sell...

But if you really want to turn us off start a conversation by telling us you would do it yourself it you had the time or could put up with getting dirty. I'm absolutely certain that I could have done brain surgery if I could have stood the blood!!!

The vacuum switchover valves (MB # 002 997 53 36) that you refer to retail for over $30 each; your MB parts guy quoted you wrong.