I have an 89 pickup 4x4 auto with a 3.0.
My rear pinion seal was leaking so I changed it out. I marked the position of my flange, pulled the pinion seal and put on the new one. I used the same pinion nut, I put it on finger right and then tightened it to 90 ft lbs, but it was about 1/4” from the crimp in the nut lining up, so I tightened it until the crimp lined back up. Now I have a vibration going down the highway. It seems to vibrate in an up and down feeling. Where did I go wrong? Any suggestions?

 

Did you happen to count how many threads of the pinion were sticking out past nut? If you didn't, then just lining up the crimp with the groove didn't really mean a whole lot. Is there any in,out play in the pinion flange now? Hopefully not, but if there is, you need to crank down on that nut some more.

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Did your drive shaft come out of phase when you had it apart?