1991 350SD slow engagement to reverse only
 

I bought another 1991 350SD, this one with 206k miles. Won it at an auction so wasn’t sure what to expect. It’s great! Very clean body, nice strong engine. Got a HG at 160k…

There are a few things I’ll need to chase down, but the obvious one to me was the slowness to engage when shifting into reverse. Like maybe 1-2 seconds. I haven’t driven it a ton, but it does shift to drive like any other MB AT, and the transmission shifts through the gears very smoothly to get to speed.

Fluid looks fine. I’ll do a fluid/filter drop after a few drain and refills to slowly get some fresh fluid in the system. But if it was a filter issue I’d have issues going forward. This is only a slow engagement in reverse issue.

Any thoughts on what it might be? Where to start?

Thanks!

Nice another rod bender, may I ask where you live to have so many vechiles?

My old 124 had the slow to engage reverse and I was told not to expect the transmission to last long at all. 21 years later it was the same box sorry can't add more than that.

New Jersey. I have a few garage buildings so that helps.

I’m not expecting anything exciting from a pan drop to be honest. If anything I’d suspect that some piston seal is leaky in the valve body. That said, my older w123 cars don’t have such issues. So who knows. I wasn’t sure if there was a systemic issue with the 722.361 AT in these cars…

Could be that the fluid looks ok, fine level, but is old and sheared I guess.

My 560SEC does that when the level is not correct (slow leak)

So I'm gonna say fresh fluid, new filter, correct level and see what happens.

Fluid filter and all that jazz won’t do anything for it. The clutch plates are bad for reverse. Been thru it plenty and rebuilt a 722.3 for that reason.

Help me to understand. If the plates are bad, they wouldn’t engage. These engage just fine, albeit slowly. Wouldn’t that imply that some piston or actuator is leaking or not working right?

The fibers are slipping, hence the delayed engagement. The material is likely worn off or you can peel it off by hand. The metal plates could also be scored. It starts out as “delayed” engagement. After a while, it continues to delay more to the point you have to floor it in reverse for it to hook, or it just goes away completely when warm. That isn’t to say that you won’t find other things inside the trans worn out as well.

I would personally recommend a full rebuild of all the clutches for 1-4 gears and reverse. Also examine everything else while in there for wear, with a rebuilt or new valve body and TC. It is NOT a difficult trans to rebuild, for your first time. You will have to take your time. There’s a DIY somewhere on google for the 722.3 I believe.

Thanks! I’m not far from you. Do you have any recommendations for any reputable mb diesel AT specialists around?

Well, they are few and far between good trans guys anymore. I knew a guy in Ewing, who was great who worked at the Benz dealer in Jersey. I may know a guy local to me who might be able to rebuild the trans for you. He’s a retired Benz tech who does side work by me. Do you want me to ask?

Whoever you find please post it here as I also have a 91 350 (how many of these even exist anymore) and reverse is just starting to take a tad longer to engage.

Sounds like my car when I got it... reverse took a long time to engage, then quit completely.

I had the trans rebuilt.

I do wonder how my 350s still exist. It might only be a couple hundred...

-J

Who rebuilt it?

Only 875 built total in 91!

I’d appreciate it! I’d be in no rush as these are hobby/enjoyment cars. I’d also be willing to assist so I can learn!

That few?

I own two of them…. You see quite a few for sale.

Slow engagement is basically perfectly normal
 

It's annoying, but my 1988 300CE was that way and my 1991 300d is that way. I bought my 1991 with 89k on it and now it has 245k or so and it still does it. Not sure why but that's just the way they are.