Difference in 8 1/4 and 8 3/4 length?

I am chasing a vibration in my 360, have replaced everything, and when pulling the balancer they noticed it had about 3/16s of end play, a little too much... I haven't pulled the thrust bearing, which is the next step, but I am wondering..

I changed rears with a a splicer U-joint on my original 8 1/4 driveshaft... the rear is raised Day 2 style... Now I am wondering if the driveshaft was a little too long and the front yoke has pushed things forward and wiped out my thrust?

I seem to remember a difference, but don't remember if it was too much or too little..

Also, can I change a thrust bearing without yanking the engine if I have access to a lift?

http://www.moparts.org/Tech/Archive/axle/5.html

about 11/16"....I didn't have a problem using a driveshaft from an 8.25" M body when I put an 8.75" in my 5th ave, still had ~ 3/4" of play in my slip yoke.

Is there a chance mine could've bottomed out and did some damage?

only if your driveline hooked directly to your engine...

no,you would have knocked the plug out of the end of the yoke itself

on the trust bearing you need to check the thrust suface of the crank as well as the bearing side clearance.

the crank/flex plate/TC can move but the rest of the tranz is not going to move.

a conversion joint of 2 diff size in 1 can cause them to vib...if thats what you have in one end of the shaft.

are you sure the ring on the damper has not sliped and is off on balance now?

have you check pinion angle on the rear and drive shaft? that could be off if its raised up in the back.

I bought a new dampener.. the old one was on the marks timing wise, but had a little wobble to it... no change with the new dampener. New everything external from the crankshaft back... flex/tc/trans, etc.. Does it in neutral and park while stopped from about 2,000 up.. ignition and related parts checked out okay, plugs fine, oil pressure great... just a vibration that I can't find the cause of..