Hard shifting + clunking transmission "fixed"!

[jbach36]

I wrote a few times asking for any possible solutions to my transmission which has been shifting hard from 1st to 2nd, and down from 2nd to 1st.

Not to mention, an unrelated problem, of my rear head rests not going down when I pushed the button on the dash.

Different possible answers came in, then as if by devine intervention, my MB mechanic shop called to say they had a sale going on, so I made an appointment. I was sure it was a vac problem. They took my car, drove it, came back, put it up on a lift. He said he couldn't work on it while I waited, so I'd have to bring it back when I could drop it off, but he did say all the vac hoses were attached, and appeared fine.

I left the shop, and it only gave a partial clunk, ...and did it only once on the way home. It seemed to be much better.

I went back today for my appointment and asked him if he did anything to it while up on the rack. He said no, and I said he must have magical powers, because it was suddenly shifting much better. He said he did give it a "right foot tune-up" when he drove it around. He said (and I'm probably repeating this incorrectly) every once in a while you have to really blow out any carbon build up otherwise you're dumping all the unused vac onto the transmission. Every once in a while, just pop it in first, and wind it out, completely out, then do the same in 2nd.

Lo and behold, the car shifts much better now. He says he can adjust the clutches if need be if the problem persists. ALSO....my rear head rests are suddenly working again! They too work on vac.

Amazing.

1991 300d 189k

[shertex]

That's really interesting! Guess I know what I'm doing tomorrow morning....

[mannys9130]

Originally Posted by jbach36

He said (and I'm probably repeating this incorrectly) every once in a while you have to really blow out any carbon build up otherwise you're dumping all the unused vac onto the transmission.

I have absolutely no idea how he came to that conclusion, or how that is even possible.

A hard shifting trans points to vacuum right away. Then when you couple it with other vac operated accessories malfunctioning (or a high idle in a gas engine), usually broken lines, worn actuators, or rotten connectors are smack in the middle of your cross-hairs.

Your best friend in old MB vacuum diag is a Mity-vac. You can do some down and dirty simple diag with just your mouth and some golf tees, but a Mity-vac is really nice to have and makes it so much easier to check out the whole vac system.

I'm glad your transmission is shifting nicely and your head rests are functional, but I do not accept your technician's explanation at all. Maybe he plugged a loose line back into place and just didn't want to mention it because it was such an easy fix?

[Mxfrank]

+1 No connection between his "left foot tune up" and the result. More likely, fiddling with the vacuum connections sealed up the system temporarily. Every ten years or so, it pays to go through the engine compartment and replace all the rubber vacuum connectors.

Originally Posted by mannys9130

A hard shifting trans points to vacuum right away. Then when you couple it with other vac operated accessories malfunctioning (or a high idle in a gas engine), usually broken lines, worn actuators, or rotten connectors are smack in the middle of your cross-hairs.

Your best friend in old MB vacuum diag is a Mity-vac. You can do some down and dirty simple diag with just your mouth and some golf tees, but a Mity-vac is really nice to have and makes it so much easier to check out the whole vac system.

[eatont9999]

I also fail to see how an Italian tune up and vacuum issues are related.

My guess is that when he did his inspection, he jiggled some vac connectors just the right way to get them to seal again. It is likely a short term solution, though.