I just had a rebuilt transmission installed in my 94 E320. The car had 107K miles when I bought it a little over two years ago and now has 134K. The last 6 months, reverse got increasingly noisy, with a loud metallic grinding noise, and it started slipping when transitioning from braking to accelerating like when going through a stop sign. I've had several W124's in the past and most of them had given me expensive transmission troubles at one time or another that were expensive to try to repair piecemeal only to have to give up and go with a full rebuild, so this time I went all out and got a fully rebuilt unit at the outset. I paid a little extra to get it from one of the top rebuilders of MB transmissions here in the US.

Now that I've had the transmission installed in the car, the original problems now are gone thankfully, however, I've had a new problem arise that my indie can't figure out. The 3-2 downshift is extremely harsh, it really slams into gear with a loud bang. It happens most frequently when quickly accelerating out of a turn when driving around town. I can get it to do it by driving along at about 20 mph (3rd gear) then stomping on the gas. Complicating matters is that it only does it about 50% of the time, the other 50% of the time it downshifts perfectly. My old transmission never did this, this is a completely new problem since the rebuild.

(Upshifts are "ok." 1-2 is a little harsh (nowhere near as bad as the 3-2 downshift) and 2-3 and 3-4 are pretty mushy. Ironically the new transmission does not upshift as well as the transmission I replaced which had perfect upshifts. Not exactly what I was hoping for after a $3000 new transmission but I can live with it. But my main concern at this point is the violent slamming during the 3-2 downshift. If I keep driving it like that, something's going to break in the driveline!)

It's been back to my indie twice for adjustments of the shift linkage and vacuum modulator, which are the only adjustment points, and these adjustments have made no difference to the hard 3-2 downshift. If it's a bad rebuild, then I'm looking at a sizeable additional labor bill even though the transmission itself is under warranty. The transmission parts are covered under warranty but any additional labor is on me. I haven't contacted the transmission shop yet as I'm hoping it is something simple that has been overlooked. My indie speculates that it may be a defective valve body in the new transmission.

Is there anything else that would cause this very hard 3-2 downshift that I should look at before I go through the trouble and expense of replacing the valve body? Would a transmission power flush be something worthwhile to try?

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1972 280SE 4.5
1984 300SD, 250K
1991 300SE, 89K
1992 300D (330K miles when KIA'd by mother-in-law 8/10/09 - still sitting in my barn)
1994 E320, 109K
1995 E420, 60K
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