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  #1  
Old 12-16-2004, 09:21 PM
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Question Transmission shudder from 3rd to 4th- '94 E420

Please help.....I need some sound advice. I have a 114K miles 1994 E420. A few weeks ago I reversed the car fast for about 200 feet, and when I shifted to forward the car shook severely. I limped home, and the shaking lessened as I drove. The car shifted between all gears, but the shifts seemed hard. When I shifted to reverse, the transmission made a grinding sound when moving backwards.

I took the car to an independent shop, and they said I needed a rebuild, which I had no option but to have them do. They said that there was a known weakness in the transmissions of the E420, and going fast in reverse caused a piston inside the transmission to break and mess up the transmission.

When I picked up the car a few days ago after the repair, it shifted fine from first to second to third, but shuddered between third and fourth. The shuddering was about four or five quick grabs before the fourth gear took hold. This was noticeable under acceleration or when going up a hill. I took it back to the shop, and they made some adjustments, but the car still shuddered between third and fourth. I took it back again, but when I went to pick it up this afternoon and drove it, it was shifting sloppily between all gears and still shuddered between third and fourth. Now they are trying to tell me this is normal and that there is nothing wrong with the transmission rebuild. There was no shudder like this before the transmission was damaged, so I can't believe it is normal.

My question is: did they do a bad job on the rebuild? Is there some other problem that could be causing this? What should I do next? Any advise would be greatly appreciated.


Last edited by JerryS; 12-18-2004 at 07:02 PM.
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Old 12-16-2004, 10:13 PM
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Sounds possible they left a teflon sealing ring out of the K2 clutch in the back of the transmission, or pinched it putting it in (can happen easily even if you're careful). Or clearance is excessive on the K2 clutch drum (possibly because the B2 piston busted, or the B2 band, but not likely). They can drop the valve body and pressure-test it on the vehicle, for a compromise at the drum seals on the K2 clutch (4th gear). There are other possibilities (valve body, etc.), but these are most likely.
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Last edited by BenzRepair; 12-16-2004 at 10:20 PM.
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Old 12-16-2004, 10:28 PM
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Sorry to hear that. I would suggest you have the transmission looked at by another professional for a second opinion. Many transmission shops will test drive your car for free and give you their impressions.
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Old 12-17-2004, 03:09 AM
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Thanks for the input, guys. Is it possible that I paid for a rebuild that was never done? In other words, is it possible to replace a broken reverse piston without rebuilding the transmission? I paid nearly $2400 for this work, and need to know whether I can trust this shop again for this and future repairs. Please let me know what you think.
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Old 12-18-2004, 06:45 PM
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Will fixing the K2 problem involve taking the transmission off the car, and will this mean rebuilding the transmission? Thanks.
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Old 12-18-2004, 06:52 PM
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A few more details on my progress. I took the car to a couple of other shops, and they were both pretty sure the trans was not rebuilt and only the broken piston was replaced. Should have been around $400 total using all new parts and including labor. However, the shudder remains between 3rd and 4th. Any thoughts, anyone? Does this transmission still need a rebuild?

Also, I just noticed on my invoice that they replaced my broken piston with a used part. Do I need to worry about the longevity of this used piston? Does it make any sense to replace a broken piston with a used one?

Last edited by JerryS; 12-18-2004 at 07:00 PM.
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Old 12-18-2004, 10:03 PM
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Even odds that you will need to worry about the longevity of that B2 piston; it is likely not the updated piston, and has a weakness inherent in that 1st version. You will need to remove the transmission to fix the problem, unless you have a valve sticking or something similar in the valve body (doubt that, though). K2 and B2 are at the rear of the transmission (means complete rebuild is necessary, basically).
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Old 12-18-2004, 10:34 PM
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A Good use B3 piston will last, yes the transmission would have to be removed to change it. Any chatter is not normal. There could be a problem in the K2 drum or another possibility is the wrong colored modulator was use or it’s not adjusted properly. Go back to the shop and insist that they fix it, Good luck.
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Old 12-20-2004, 01:32 PM
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Is the B3 piston also called the reverse piston? I had all these problems surface after I reversed the car fairly fast for about 200 feet and then shifted to D. It was fine going back, but the moment I shifted to D and began to move forward the whole car began to shake and vibrate. Could I have damaged the K2 clutch by going fast backwards, and also broken the B3 or B2 piston? I'm not sure what these pistons are and what they do. The invoice I have said the 'reverse piston' was replaced (with a used one). Thanks.
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Old 12-22-2004, 07:30 PM
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The B3 piston is the reverse piston. In most cases you can repair a no reverse failure by simply removing the pump .The transmission does not have too be totally disassembled.
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  #11  
Old 12-22-2004, 08:30 PM
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Strange thing is that the reverse gear worked fine, except there was a scraping sound coming from the transmission when I reversed. The main problem was the pulsing/jerking I had going foward in all gears. The shop claims they did a complete rebuild on the transmission, but I now have the 3 to 4 shudder, and also discovered I no longer have a kickdown. The shop now tells me it might be a valve body problem. Does anyone think they tried to repair the car on the cheap and missed something?
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Old 12-22-2004, 09:32 PM
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Read my last post, the B3 piston broke because it rubbed against the K1 drum. I am sorry to say you did not get a quality rebuilt transmission. That transmission has to be removed and done over. The valve body on very rebuilt should be totally disassembled and rebuilt.





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  #13  
Old 12-23-2004, 11:37 AM
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Thanks for the advise. I took the car to a Mercedes dealer for a diagnostic, and they also said the transmission needs to be competely rebuilt again. I found out that the original shop I took the car to had sent the transmission out to a small shop for repairs, and I spoke with this guy. He wants to put a valve body he took off a 420 SE on my car to try to fix the problem. Of course I'm not happy about putting a used part on my car; sounds like a recipe for another failure in a year or so just out of warranty. I'm considering my options at this point. I'm trying not to let this ruin my Christmas!

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