I've been chasing a vibration issue with my car for almost a year now and I finally found it. I have a 1962 Chevy Nova with a 383 TPI and a Tremec TKO 600 and a 8.2 with an Eaton posi and 3.55 gears. I really didnt notice it much when I had the 3.08 gears because it was up around 80 to 90 when I changed the gears it was around 60 and 70. So I stated with the obvious and balanced everything tires, driveshaft replaced the ujoints transmission mount. Check the angles and corrected them. Put new axles in since there was a slight wobble had a new 3.5 alum driveshaft built. Found out the trans yoke was to short and wore out the rear bushing new bushing, new yoke still vibration. Took the alum shaft and had it re balanced by another shop Inland Truck, still there. Had a new steel shaft built by Midwest Wheel still there. put all new bushing in the rear axle spring pads etc. Still there. I was checking around and got my dial indicatior out and checked the run out in the shaft. There was .023 at the trans and .001 at the rearend witht he new steel shaft so I pulled it our and checked the alum and it had .019 in the front and .010 in the rear. Finally I called Jeff Dusek with Driveshaft Specialist Inc http://www.driveshaftspecialist.com/
in San Antinio TX. I explained everything to him and he said it was my driveshaft. I'm thinking how could that many driveshafts be bad. He said something that I never thought of. You had a "TRUCK" driveshaft builder build it. Well I'm turning around 2100 rpm at 70 mph so with my .64 overdrive the shaft is spinning at 1344 rpm. Truck drivshaft dont have to be so balanced because they dont spin very fast.
So they built me a new shaft and it works great. So if you need a driveshaft build please contact them.