Thank you for the quick replies. Couple of quick answers: the transmission is a three speed on the column and is the Borg Warner R-10 type (the serial numbers on the trans start with “GM” so my assumption is that GM had the rights to use/sell the BW product/design under the GM brand). The severe shudder/chatter does not get better as the clutch is released – if anything, it gets worse to the point where you have to quickly push the peddle back in or kill the engine and shutter to a stop. The shudder/chatter is so bad it feels like the entire engine/trans/drive line is going to fall apart. First gear is low, but it’s not as low as the typical “granny gear” in a stock four speed Advance Design truck (I’ve owned one before).
As I mentioned, we did replace the front engine mounts, but did not change the rear because they looked o.k. We will change the rear mounts this week, but that sounds so simplistic to fix something so severe as what I’m experiencing that I have my doubts that will fix the problem. Hopefully, I’m wrong. I’ve ordered two different sets because they’re cheap and I want to see the quality before installing them: one from “The Truck Shop” in Orange, CA and another set from “The Filling Station” in Oregon. I live in San Jose, CA and this is my third ‘50s/‘60s Chevrolet truck (I’ve also owned a stock five window’52 and a ‘53 Suburban which I converted into a resto-mod with a 350 engine and trans and a Camaro front clip.
As far as the adding another cross member, that thought came after working under the truck and looking at how weak the current set up was. There’s approximately three feet between the cross member from the engine to the transmission. One of the techs at The Filling Station said he thought this was a known design flaw in the “second series” trucks.
Finally, the idea of opening the hood and observing what’s happening while the truck is shuddering (and purposely trying to get it to shudder), we tried that too and it looks like the engine moves at least 1/2 inch forward and backward (rather than a normal running engine slightly moving side to side). That’s what prompted the idea that it could be a rear motor mount problem and/or cross member.
