I have a 31 spline 8.8 out of a 04 level II. it had a slight vibration at about 75, but i didnt think it was anything to be concerned about UNTIL it pitched the rear driveshaft on the way to the jackson meet. i want to check the flange on the end of the pinion for runout. How much should i allow before being concerned? i ordered a new driveshaft and a new tailshaft for my trans since it broke it almost in half, but i still need to fond the source of the vibration

 

i think you cracked your flanges(not sure the name) when you changed the Ujoints.

 

I didnt crack the tailshaft. i used the wrong term. i cracked the extension housing that is between the trans and the transfer case. I did u-joints about 2 months ago when i still had the 7.5 and drove it about 500 miles without a problem before i did the 8.8 I am absolutely certain i didnt leave a bolt loose because when i took it apart last night, every single bolt i took out was tight. my vibration started the day i put the 8.8 in. im still thinking that there was rust or soemthing between the two flanges (the one on the pinion and the one on the driveshaft) causing it not to run true. i will make certain that i clean them both thoroughly (sp?) before i assemble it. I still have to check the pinion flange for run out. is there a gasket that goes between the t-case and the extension housing? it appears that there was one.

I will try to get some pics up. i dont have the broken driveshaft to take pics of but i post a pic of the extension housing

 

there is a gasket there but i just used some black silicone to seal mine back up

 

Definitely clean up the mating surfaces before reassembly.

Another thought: the factory matches the driveshaft yokes to the axle and t-case flanges and the parts should always be marked on disassembly so they go back together in the same orientation.

In your case, installing mismatched parts from 2 vehicles could cause a runout or imbalance stackup that would vibrate worse than on either of the original vehicles. You can try unbolting and rotating the driveshaft yoke 90, 180 and 270 degrees relative to the axle flange to test for the sweet spot. Same procedure at the transfer case flange.

 

thanks bob. i marked it the first time when i did the u joints and i didnt have a problem. now i just gotta guess when i put it back together.