The original post from two years ago was revived recently but got off topic so here is a new thread and a link to the old one.
Vibration assistance needed - Manual Transmission Related?
It seems that many auto to manual conversions suffer from some vibration issues. While many of the suggestions dealing with balancing the driveshaft, changing the bearing mount, making sure there is no metal to metal contact, etc, have been somewhat helpful, most of the vibration was still present at least when I tied it.
I found a friend with a european 300D with a 4 speed manual. When I looked at the way the tranny was mounted I was surprised to see that the transmission crossmember/mount was NOT like the 240D manual, nor was it like the 300D automatic. Nautrally, I swaped in the euro cross member and mount into my car and low and behold, 90% of the offending vibrations went away.
There was not much hope is visiting the yard to search for a euro 300D manual, but I thought that, Germans being Germans, mbz might have used the same crossmember on a 240D AUTOMATIC!
It turns out to be true, the 240D Automatic transmission crossmember is the same as the 300D european manual crossmember. The mounts themselves are indeed different, the 240 has narrow mounts, while the 300 has a thick mount, close to twice as thick.
So here is another piece that no longer needs to be fabricated for the conversion. I am still experimenting with different mounts, there are quite a few versions, but even with my old auto trans mount the large majority, but not all, of the vibrations have been eliminated.
Here is a picture of the 3 different crossmember types. (You can ignore the bar that is attached to the auto 300D mount, that was my old mounting solution.)