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1995 S420. 309,000 miles.
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23 Posts
Discussion Starter · #1 ·
Last night, pulled into neighbor's driveway, put her into reverse to back into my garage and nothing. All forward gears work fine, flawlessly, actually.No indication of failing bands and clutches.

I've spent the better part of my morning reviewing threads and pdf's relating this common problem with the reverse seal tearing or o ring in valve body? Service bulletin says check plates and sealing rings on brake B-3 piston...

309,334 original miles on the drive train. I suspect the seal finally wore out.

Please throw some opinions over here.
 

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99" CL500 , 99' CL500, 97' S500, 01' S500, 02’ G500, 09’ G550
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2,171 Posts
MAVA, or Martin is a local bay Area guy, and may be your best bet to figuring out the issue. Hes on the forum regularly and has been more than generous in helping guys out with tranny issues. Im sure he'll chime in any time now.. lol
 

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93 SL500, 95 SL320, 96 S320, 98 S500, 2002 E320 4Matic Wagon & A little 91 5.0 FORD Mustang
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9,043 Posts
Bruster,

Sadly, it is a small(2 inches or so in diameter) o-ring with a lip on it. It just tears with time, but if you lost reverse completely, and you have no reverse when the car is cold. The lip on the o-ring has completely been torn off...

Lucky you, yours failed at 300k, mine was shot at 130k, and I rebuilt my transmission myself earlier this year for that, and I'm about to do it again on another benz.

At 130kmiles, half of my clutches were worn, so I replaced all the clutches, but my brake bands were like new, so I did not change those...Their are a few updates on that transmission that should be changed. I would defiantly put in a new B2 piston for sure, and a new torque converter too

While you are fixing your transmission, change out the rear main engine seal, bracket, and bolts. Mercedes improved the design of the rear engine seal, and it is waaaaaaaaaaaayyyy better than before...

Here is the picture of the reverse seal(the inside seal on step7 is the culprit):

http://www.benzworld.org/forums/w140-s-class/1369461-722-5-transmission-oil-pump-rebuid.html

Martin
 

· Registered
1995 S420. 309,000 miles.
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23 Posts
Discussion Starter · #5 ·
Martin,

Thanks for the response. You're the one who wrote that you drive yours around town without reverse in one of the threads!

I can hear it going into reverse but nothing...you're 100% set on pulling it apart? Even before dropping the valve body? I'd like to get this resolved this weekend.

Mercedes Mechanic seems to think valve body first then R&R.

Corey
 

· Moderator
93 SL500, 95 SL320, 96 S320, 98 S500, 2002 E320 4Matic Wagon & A little 91 5.0 FORD Mustang
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9,043 Posts
Corey,

I drove for about a year with no reverse, but finally one visiting in Livermore. I got stuck, and it took me half hour to move the W140, and that was it...

Now, my reverse went from working to this roller coaster sound, and then nothing after it warmed up. "Per" the third-party service manual I had the classic lip-seal failure.

Read this old thread below, but download master.pdf on post 26, and look at the trouble shooting section..

http://www.benzworld.org/forums/w140-s-class/1407863-no-reverse-jerks-reverse-when-cold.html

Now, The poster-dapet07. Had the same thing I had. In post 15 with the three pictures. The picture with part facing down, and the six legs up. The shinny points on the inside are because of the roller-coaster sound-the clutch pack is hitting the part.

Post 22 are the reverse clutches, and the clutch where his right thumb is at is very worn as mine were the same because the lines are gone like the ones from his left thumb.

Again, I'm not there. This is a thread about the 722.5, but this is common to 722.3-772.5 as the internal parts are the same with both transmissions.

Best of luck,

MArtin
 

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92 W140 300SD 97 VW Jetta TDI 05 E320 CDI 90 Passat Wagon TDI
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1,280 Posts
There are several threads that discuss this issue. It has to do with the poor material used in the reverse clutches and how it degrades quickly.

I've been driving without reverse for a long time although I don't use the car all that often.

One of these days when I'm feeling adventurous I will endeavor to repair mine.
 
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