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  #1  
Old 11-18-2005, 11:17 AM
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Join Date: Oct 2005
Posts: 36
Cold weather loss of reverse

It was 5 degrees this morning. No problems starting my 79' 300sd, but couldn't get the car to back out of the driveway.
Managed to push the monster back to where I could put it in drive and swing around. Drove for about 5 min. pulled into a parking lot to test it, and sure enough reverse worked.
Is this a common problem with the older MB's? any advice for how to warm the tranny or repair this problem? Also, can anyone explain why forward works, but backward doesn't??????

Thanks!

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  #2  
Old 11-18-2005, 11:22 AM
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Join Date: Jul 2004
Location: York, PA
Posts: 621
This is showing you that there is a part of the tranny worn too much so that when the fluid and the tranny are cold that reverse does not engange, when hot things expand and thus everything works. See when everything is cold it shrinks, when hot it expands. I had a similar problem many moons ago in an old Mercury Lynx where the tranny would not shft out of first until it warmed up then it was fine. On that one it was a worn plastic Governour gear, when hot it expanded and worked fine, when cold the Govenour did not spin as the gears were seperated just enough to allow it to no longer mate properly. Not sure how the MB trannies really work as I have never taken one apart. Probably a clutch band slipping in it.
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  #3  
Old 11-18-2005, 08:13 PM
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Join Date: Jul 2004
Posts: 43
I thought I replied to this post before, but I don't see it now, so maybe it didn't go through.

Having reverse go out seems to be a common weak point of M-B transmissions. In my case ('91 420SEL), reverse started taking longer and longer to engage (seconds), until it wouldn't engage at all. Problem was with the B3 reverse clutch. It turns out that the transmission in my car (622.3 tranny, if I am remembering the number right) uses a reverse clutch, which has no external adjustment, and requires opening up of the tranny to repair. Mine went out at 165,000 miles or so. Repair cost about $1300, and the car now has 182,000 miles on it.

But, older 622-type trannies (622.0, 622.1, 622.2) have an externally-adjustable reverse band. I am guessing that a late 70's car would have one of the above in it. If I remember right, the adjustment is on the passenger side of the tranny housing, and is reachable from under the car. It basically looks like a threaded stud, with a locknut holding it in position. Some transmissions have a screwdriver slot already in the end of the stud, and so you just have to undo the lock nut to be able to adjust it. But I seem to remember that some cars don't have the screwdriver slot.

I can't tell you what the adjustment procedure itself is - but I'm sure if you search the forum you will find mutiple posts (try "reverse band adjustment", or variations of that). (It is something on the order of "tighten the adjustment screw/stud to X ft-lbs of torque, and then back off Y turns.") This may or may not solve your problem, but it is at least a low-cost thing to investigate and try. The adjustment IS supposed to help with slow engagement of reverse.
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  #4  
Old 11-19-2005, 03:26 AM
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Join Date: Jul 2003
Posts: 78
here lies your answer

reverse problems on 80' 300D

best of luck...

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