W126 reverse slipping - PeachParts Mercedes-Benz Forum

LandYaghtLover · #1 08-19-2010, 11:35 PM

Fluid looks good and at right level. All forward gears seem fine, to me. No vac leaks that I can tell of. It only in reverse. At first I though it was a brake problem, like a pad catching because that is exactly what it feels like. But I decided to hold it in reverse and just let it idle for a while. There is a "whirling" sound coming form the trans (I think). And the car will catch reverse slowly. Although tonight it jerked hard into reverse with barley any throttle input.

Ideas? I hope I am not loosing reverse, but I am betting its a trans issue. I am VERY new to this car and know little.

Hit Man X · #2 08-20-2010, 12:37 AM

Reverse is usually first to go on the 722.3 for whatever reason.

What sort of miles on the unit?

LandYaghtLover · #3 08-20-2010, 12:38 AM

Odometer reads 138k.

What is involved in transmission replacement? Any clue as to an approximate price? Or can I rebuild it?

Hit Man X · #4 08-20-2010, 05:47 AM

Quote:

Originally Posted by LandYaghtLover

Odometer reads 138k.

What is involved in transmission replacement? Any clue as to an approximate price? Or can I rebuild it?

Does the odo actually work?

Dropping driveshaft, crossmember, unbolting torque converter from flexplate, dropping the trans...

Price on paying someone to rebuild it? $1000-1500. If you are asking if you can rebuild it, I already doubt your skills. Not to be a downer, but it is not like just changing brake pads.

Most of the labor on a rebuild at a shop is the actual removal and installation of the unit, figure that $300-500 easily. A full rebuild kit is around $300, plus/minus $50 or so.

I would not go through all that hassle just to only replace the reverse clutch pack then reinstall the trans. Since you are already in there you may as well go through the rest of it if you plan to keep the vehicle.

pawoSD · #5 08-20-2010, 06:55 AM

I had reverse fail last year on mine, same whirling/swishing sound. Mine had 281k at the time though.

LandYaghtLover · #6 08-20-2010, 09:15 AM

Ya. Odometer works. I figured I could rebuild it since I have already done an engine and a trans on a Ford. But it some cases I know rebuilding is just not worth it, thats what I sorta meant. But if you already doubt my skill maybe I will just toss this thing on CL and call it a day.

Peter Guenther · #7 08-20-2010, 09:56 AM

It is common mine failed on my 92 at 100K, slow to engage and then bang. It is something about the front clutch, MB does not repair they just replace $4k, no converter, 2yr 24k warranty. You could save by having a "good" shop rebuild it for less money. They have to loosen the exhaust and they replaced the trans lines and motor mount.

david s poole · #8 08-20-2010, 01:36 PM

just pulled my trans out of my 91 420sel.same problem only mine was so bad that in order to make car move in reverse you needed someone to give a little push.anyway,it was exactly what i suspected-----no meat left on the reverse clutches.apparently my timing was perfect as no marks on the steel plates either.3rd gear drum clutches still had part numbers on the surface and were good.there were no issues with forward speeds so replaced reverse and drum and band,put back front pump and it drives fine with instant reverse engagement.while trans was out i found my pesky oil leak at the rear main seal so threw a new one in.

S-Class Guru · #9 08-20-2010, 01:47 PM

Yeah, welcome to the 722 tranny. The reverse clutch plates just wear out sooner, due maybe to the super low gearing/torque load as they drop into gear.
I was one of the successful ones, I guess. I caught the problem early, when it just got a bit slow going into reverse. I ordered up a kit, dropped the tranny, went into the front, and the first thing looking at me were the worn out reverse plates. Pretty easy to get to and replace. I just didn't see the need for the extra risk of taking everything else apart, since it all looked and worked great, and my labor was free if I needed to go back in later.
(I actually did go ahead and replace the 2nd gear plates also, and had a little issue with them shifting different. Wish I had left them alone, they looked new).
But, as stated above, If you don't really love crawling under cars as a hobby, and don't have plenty of tools, jacks, time, and some experience in trannys, then probably buying a rebuilt is the best bet. As I said, the reverse plates are quick and easy when you get the tranny on the bench, but I wouldn't do just that if I was paying a shop to do all the R&R labor.

DG

LandYaghtLover · #10 08-20-2010, 03:10 PM

So R&R at maybe 5 hours for this? A ford trans I know, a benz trans I have never been in. I would LOVE to do the work myself really. I bought the car with the intent of it being a "hobby". Just did not expect front sway bar failure AND the reverse to be problems in the first 5 days of ownership! lol

You comments make me confident that this may be easier to take then the Ford ones. I will crawl under and see what has to be done. Fun fun!

Hit Man X · #11 08-20-2010, 04:58 PM

Quote:

Originally Posted by LandYaghtLover

So R&R at maybe 5 hours for this? A ford trans I know, a benz trans I have never been in. I would LOVE to do the work myself really. I bought the car with the intent of it being a "hobby". Just did not expect front sway bar failure AND the reverse to be problems in the first 5 days of ownership! lol

You comments make me confident that this may be easier to take then the Ford ones. I will crawl under and see what has to be done. Fun fun!

Well it is a 20 year old car with no records, expect anything.

PM me with your email address and I will send you the PDF file for the 722 transmission

OM616 · #12 05-11-2011, 05:44 PM

Quote:

Originally Posted by S-Class Guru

Yeah, welcome to the 722 tranny. The reverse clutch plates just wear out sooner, due maybe to the super low gearing/torque load as they drop into gear.
I was one of the successful ones, I guess. I caught the problem early, when it just got a bit slow going into reverse. I ordered up a kit, dropped the tranny, went into the front, and the first thing looking at me were the worn out reverse plates. Pretty easy to get to and replace. I just didn't see the need for the extra risk of taking everything else apart, since it all looked and worked great, and my labor was free if I needed to go back in later.
(I actually did go ahead and replace the 2nd gear plates also, and had a little issue with them shifting different. Wish I had left them alone, they looked new).
But, as stated above, If you don't really love crawling under cars as a hobby, and don't have plenty of tools, jacks, time, and some experience in trannys, then probably buying a rebuilt is the best bet. As I said, the reverse plates are quick and easy when you get the tranny on the bench, but I wouldn't do just that if I was paying a shop to do all the R&R labor.

DG

Anyone feel free to answer.

I am going to have to go into my 420sel trans to do the B3. I really don’t want to buy a "rebuild kit" when I only want the B3 clutch and piston seals.

Can anyone recommend a source to get the B3 clutch components?

Thanks

david s poole · #13 05-13-2011, 11:32 AM

dealership will have those parts and are only moderately expensive.but you will get oem clutch plates which can be an issue.

OM616 · #14 05-13-2011, 03:11 PM

Quote:

Originally Posted by david s poole

dealership will have those parts and are only moderately expensive.but you will get oem clutch plates which can be an issue.

Searching I found a post with the B3 piston seal kit part number for the 722.4, # 201 270 48 01

I also found a couple suppliers on line where I can get the disks for about $7.00 ea.

A friend of mine has an air conditioned shop with a hoist, so when he has an opening, I will take a couple days and do it.

I almost have a thought of putting together a B3 kit.