'94 E320 hard 3-2 downshift after rebuild
 

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?

you may have already seen these but the adjustments mentioned here have really helped me get the falcon back in shape since I got it back from the rebuild. I haven't even touched the modulator yet.

I found that when I adjust the throttle, I have to confirm the two metal arrows are dead center and that the cables have no tension. any movement of throttle control will affect the position of the bowden cable arrows.

I found this but didn't read all the way through so only use it as a guide.

http://www.benzworld.org/forums/w201-190-class/1361737-diy-mercedes-722-3-722-4-a-5.html

After further thought and discussion with my mechanic and talking it over with the rebuilder of my tranny, we decided it is probably something inside the valve body that didn't go right during the rebuild. He thought it's probably the k1 accumulator getting stuck. The rebuilder is sending out a replacement valve body that my indie will install. I'm sure glad I dealt with a reputable rebuilder because it was no hassle, in fact he suggested sending me the new vb right away. I'll repost with an update after the new part is installed. Thanks everyone for the suggestions

'94 E320 hard 3-2 downshift after rebuild
 

Let us know how the new valve body works out. That thump downshift is something I've dealt with before, if the valve body fixed it then that's new info we want :)


Thayer

Great news. I explained the issue in detail to the transmission rebuilder and he said right away that it sounds like the K1 (IIRC) accumulator was faulty in the new valve body, that something must have gotten messed up during the rebuild. He said that he would immediately build and send out a new valve body to my mechanic, under warranty, free of charge.

A few days later, the new valve body arrived at my indy, and a week later it was in the car. I got it back today and drove it all over town giving it a thorough shakedown, and I am happy to report that the issue is completely resolved. Not only are all the downshifts perfect, but the upshifts are even a little better too. I can truly say that the transmission functions perfectly now. Hooray!

So it was indeed a faulty rebuilt valve body. Icing on the cake is that the rebuilder was absolutely responsive, cooperative, and couldn't've treated me better.

Thanks everyone for the help. It's good to have my beloved E320 back better than ever! :)

Would you mind posting who your trans rebuilder was?