722.120 Trans Losing Reverse - PeachParts Mercedes-Benz Forum

rs899 · #1 11-09-2007, 09:17 PM

OK guys, here's the little gem of wisdom I have for you direct from the ATSG manual on adjustment: " Tighten adjustment screw 0.5 mkp and then back off by 1.75 turns. Lock adjustment screw by means of counternut"

DON'T ask me what an mkp is.

RayM.- I would be very reluctant to remove the adjustment screw. There appears to be a separate pin that rides between it and the band that could very well slip off and end up in the case. Tread lightly here.

ray m · #2 11-09-2007, 11:38 PM

Quote:

Originally Posted by rs899

OK guys, here's the little gem of wisdom I have for you direct from the ATSG manual on adjustment: " Tighten adjustment screw 0.5 mkp and then back off by 1.75 turns. Lock adjustment screw by means of counternut"

DON'T ask me what an mkp is.

RayM.- I would be very reluctant to remove the adjustment screw. There appears to be a separate pin that rides between it and the band that could very well slip off and end up in the case. Tread lightly here.

I had no choice but to remove it slowly. Even after removed I couldn't adjust the nut on the bolt.
I found this:My 300SD wont go into reverse
message 6 gives a great direction. I tried it but no luck. I could not get the nut off of the bolt or budge from its position on the bolt. I removed it all together and replaced it with another from one of my parts cars. I tightened it all the way the tried it at every 1/2 turn up to 4 full turns. ( raise car ,turn ,lower and start) No luck. I'm beginning to believe i need to remove it again and file a 1/16 to 1/8th off the end so that when I replace it ,it will tighten in farther.I'll put a pic on the post to show what i mean. In side the inner cylinder it is about 1/2 deep. at the base it looks like a pin has worn down a 1/8 inch depth indention. I'm thinking that if i shave off 1/8 inch off the length of the bolt It would tighten down to the correct position to back out and achieve reverse. I don't know. Does anyone know any better to guide me. The frustration level is mounting. Thank goodness it goes forward, even if it goes forward now in Park & Neutral. Seems to be no 1st.gear. It feels like it starts in 2nd. And L is like park. Darn But it still goes FORWARD and has for 3 weeks now. I'm tempted to leave well enough alone until I get better direction. RAY M.

rs899 · #3 11-10-2007, 02:14 PM

Guys-

Here is a through-section shot of what the business end of that adjuster does. This is a 722.1xx parts tranny I have under my bench. ( The bellhousing has been removed and you are looking through where it would normally be into the case from the front of the car). The right side of that stud touches a strut that contracts the B3 band around the drum. By cranking that thing in you are adjusting for wear of that band. The servo that compresses the band acts on the other end of the band from the other (driver's ) side of the case.

The band is that vertical bit on the right. Yes, there isn't anything to grab on to to adjust on this tranny either.

Rick

sedecrem · #4 11-10-2007, 03:22 PM

On mine I just cranked on the nut until it was tight, and that gave me reverse. I think the bolt just went along for the ride. The nut was likely frozen on the bolt just as yours is. A couple of weeks ago I did a search on eBay and found an adjusting bolt that looked just like the one on the picture. I think the key works I used were "722.1" and "transmission". You might give that a try.

It is also possible there is more wrong with your transmission than just the adjustment of the band. If you can find a good Mercedes mechanic they might be able to figure it out for you.

Hope it works out for you.

ray m · #5 11-11-2007, 02:15 AM

Quote:

Originally Posted by rs899

Guys-

Here is a through-section shot of what the business end of that adjuster does. This is a 722.1xx parts tranny I have under my bench. ( The bellhousing has been removed and you are looking through where it would normally be into the case from the front of the car). The right side of that stud touches a strut that contracts the B3 band around the drum. By cranking that thing in you are adjusting for wear of that band. The servo that compresses the band acts on the other end of the band from the other (driver's ) side of the case.

The band is that vertical bit on the right. Yes, there isn't anything to grab on to to adjust on this tranny either.

Rick

Can the "servo that compresses the band acts on the other end of the band from the other (driver's ) side of the case" be changed or replaced in some way maybe correcting all of my shifting problems. .
I can see that it would be of no use to shorten the bolt stud.

rs899 · #6 11-11-2007, 07:23 AM

If your reverse is slipping, you need to find a way to increase the force on that strut, either by turning in the threaded portion of the stud ( the one that doesn't ever seem to be with a head) or by replacing the strut with a longer one, or possibly by adding something between the stud and the strut.

I do not believe that the strut is threaded- it is just a solid piece like a finishing nail . It may fall into the case if you remove the adjuster, but maybe not. Ray seems to have a picture of it in place.

Ray- it is possible that your problem may be at the servo end-or it could be something else....

Rick

anyone figure out what an mkp is?

TdTno499 · #7 11-14-2007, 02:14 PM

mkp is German for kgm, basically.
Kilogram-meters, like our foot-pounds, a measure of torque (which you knew). The German translates as "meter-kilopond", and they are equal. They equal 7.233 ft./lbs, or 86.796 in./lbs.
Newton-meters are different. Approx 1/10th.
1 nm = .73756 ft./lbs., or 8.851 in./lbs.
So, the band adjuster gets tightened to 3.6 lbs./ft. (or 43.4 lbs./in.), then backed out 1-3/4 turns and locked.
Lots of luck getting a torque wrench on that!
I'm surprised the book didn't say some thing like, " turn the adjuster bolt until it shears off, the find a way to back it out 1.75 turns..."

PETE

ray m · #8 11-18-2007, 04:59 PM

It's off the ground so i can check it easier. How do I *(jump the solenoid from the connector on the wheelwell (Have someone in the car to apply the brakes!),*
The shifter was shot when I removed it. I replaced it with a good one and it moves more solid. Didn't help. I compared linkage positions on both of my 80 300d's and the look the same. I took pic's of each position and thay looked the same. I started over again form a fully tightened adjustment bolt and tried it at each 1/2 turn up to 2 1/2 full turns. The only change i got was that when i shift back into park and release the brake it gives a tapping or grinding noise until i apply the brake again then it locks into park and doesn't go in forward like it use to. There are 4 wires that is attach to the box where the shift linkage attaches to the trans. Could that have any thing to do with the shifting. If I replaced that box could it help or will I ruin the shifting. Is it complicated to replace. I'll put a pic on the post to show the wires and part . If the part in the pic is replaced easily I have a replacement one. Could that help. RAY M