722.120 Trans Losing Reverse - PeachParts Mercedes-Benz Forum

TdTno499 · #1 10-22-2007, 05:21 PM

Reverse has been taking a long time to get moving for a while now. Better when warmed up. Fine for parallel parking, but no longer when it's uphill! Anybody with experience on this transmission that can tell me if this is fatal?
I've heard that an internal pressure leak could be causing a band to not engage fully, possibly curable w/out dropping the unit. Also heard that in the later boxes, this was due to deterioration of the reverse clutches, and is fatal. If clutches are the problem, I'll see abundant clutch material in the pan when I drop it.
Near Philadelphia if anybody has one of these, known to be good. (used in 116-bodied 300SDs)

PETE

rrgrassi · #2 10-22-2007, 05:24 PM

Sometimes it can be fixed by adjusting the B-2 band, I have been told. I have the 722.3xx tranny.

rs899 · #3 10-23-2007, 01:31 PM

Reverse has an adjustment on the 722.1xx. It is a locknut type stud on the passenger side of the case in front above the pan. I would see if the whole thing backed out (like it did on the 77 240D I bought for cheap "without" reverse), or can be adjusted in a half turn at a time.

TdTno499 · #4 10-24-2007, 11:59 PM

Thanks, Admiral, that's the kind of answer I was hoping to hear!
Is this a band adjustment? When you say "in front", does this mean "facing forward?

PETE

rs899 · #5 10-25-2007, 07:29 AM

not sure what you mean by "facing forward"?

passenger side of the case, above the pan.

As you are looking at that side of the case, the bolt is toward the right, closer to the "thick" end of the tranny. I believe it may be a four-sided stud with a six sided locknut , but I don't recall the details.

TdTno499 · #6 10-26-2007, 05:43 PM

Still anxious to check this out...if it ever stops raining here.
Haven't heard that I can test the working pressure externally on this or what the spec is for that yet.

PETE

pimpernell · #7 10-27-2007, 09:59 AM

Had the same thing happen to my prior 240D in Florida, my reverse went south. Took it to an independent mechanic, who put it up on a lift, and said that the adjustment nut had backed out for the reverse gear. Made a minor adjustment, locked it down, and presto, reverse was back in action. This guy had the "nerve" to charge me $26.00 for his time and labor. Needless to say, this did not sit well with me, and I did pay him what I considered a "fair" price above what he was asking for. Good luck with your car....

rs899 · #8 10-27-2007, 12:32 PM

...so you would have been happier if the mechanic had told you it needed a rebuild.

Jeez $26 and honesty......I mean his time, expertise and tools (rack) are worth something....

TdTno499 · #9 10-31-2007, 10:15 AM

Not having a lift, I used the jack method last night to have a look for this adjuster, and didn't see a likely candidate. Above the pan on the passenger side is what looks like a pressure check valve of some sort. It comes out of the case at about a 45 degree angle, has a large, perhaps 27mm-headed bolt capping the end, and an electrical connection on the side.
I am assuming this is not what I'm looking for. Does anybody know what this is?
Plan on getting the car down to my garage in the next couple of days to get it safely jacked up a bit higher to have a better look.
Any more clues are appreciated!

PETE

sedecrem · #10 10-31-2007, 01:13 PM

TdTno499

I think the item you are looking at is the kickdown solenoid. Just above it is the band adjusting stud. You can actually see it from the engine bay looking down on the right(pasenger) side of the transmission. At least that is where it is on my '82 240D. There is a threaded stud with a 17mm locknut. On mine it looked like the tip of the stud sheared off. However, just by tightening in the lock nut a couple of turns with a socket I got reverse to work where before there was no engagement at all.

The guy I bought it from sold the car because a Mercedes mechanic told him it would be $2800 to rebuild the transmission without even looking at the car. Also the brakes were trashed. It needs front rotors and calipers. However the body is very straight with no rust and the interior is about 90%-95%. Has 210k miles on it and the engine seems to run well. Only real negative about the car is that someone threw a cheap paint job on it that is fading/peeling off in places. But I only paid $1,000 for it so I figure I can afford a decent paint job.

TdTno499 · #11 11-01-2007, 11:59 PM

Would have been happy to pay the $26 that Pimpernel's wrench wanted to charge, but I don't know any transmission guys that I trust that much to even ask.
If it's not much trouble, could you see if there is an adjustment for the other band while you're looking. As long as I'm doing tranny care, I should check it. Reverse is working well, and maybe I'm just not used to it any more, but it seems "fast" at idle...hard to explain. I'll have to live with it a bit, don't drive around in reverse much around here.
Might even do the pan gasket and filter anyway, since I've been sitting on the parts for some time now. See about that.

PETE

rs899 · #12 11-02-2007, 10:18 AM

Sorry- there are no other band adjustments. The others are adjusted via replaceable little studs of varying lengths from inside the case. I did a quick look at the book this morning before work and I didn't find the adjustment in there. I think it says something about it, but I will need to study it a bit more.

ray m · #13 11-02-2007, 10:16 PM

I looked for the bolt and found the bolt I outlined in the picture. The small bolt that is in the other pic was attached to the end of the bolt that the adjusting nut is on. As i tried to unscrew the small bolt, it broke off with little pressure,like it was already half sheered. I figured I had better stop and find out where to go from here. I have 2 part 300d's and both of them have no outer bolt like the one that sheered off. They have probably sheered off long ago. Do I tighten the nut for the adjustment or tighten the bolt some way to make the adjustment to get reverse back. Hopefully the pis'c help everyone out. Ray M

ray m · #14 11-02-2007, 10:24 PM

sorry here are pics mentioned above RAY M

TdTno499 · #15 11-05-2007, 11:45 PM

Ray,
That is very interesting. I was wondering how you were supposed to turn the adjuster with no slot or hex, only the "nipple" , apparently left over when the adjuster sheared off of my bolt years ago. This answers that question. Maybe Admiral Rick will get back to us soon with the spec from the book. Meanwhile, could you show the broken off view of that bolt? It looks like it was designed to break off if you torqued it too much. Mine was loose enough so that I could turn it in with a screwdriver on the flats of the locknut. Don't think I got it locked down too tight, though.

PETE