I took the shaft out last night, then re-installed it. I measured/estimated that the tongue/slip engages about 2.5" of tranny spline (tailshaft?).
I know it should be more like 4.5" however I'm still not conviced this is whats causing my vibration. Maybe... but maybe not, I dont know.
The ENTIRE drivetrain was not replaced, just the driveshaft and rear end. I was already running my new 360 and a-833 without vibration for about a year... on the original 7 1/4 rear end... probly 2.94 gear.
Thanks for you help! PS - I already had the shaft balanced (and they replaced parts of it which cost me close to $200). The shop claims they shortened it according to my request (2") and tells me I'm to blame for giving wrong instructions. I wish I had given written instructions and dimensions instead of just verbal... cuz I'm convinced they screwed up and shortened it too much. Is it possible to get more length out of it? Change the slip or something?