do you get vibrations from a lift? I bought an 89 that has either a 3 or 4'' rancho lift and at approx 57 mph and above I get bad vibs from the rear. I will also note that this has an extended slip yoke. Do you think this could be the source? Maybe I could go to a stock yoke and drop the TC to remedy this it is a 98% DD. Thanks in advance.

 

your u joints are probly toast. thats the first thing i would check. cheap and easy

 

Ujoints ball joints tires need balanced possible alignment bad shocks could be one of these

 

Check angle of rear axle in comparison to t-case. Rear drive-shaft u joint angles may be too severe.

 

Whats a extended slip yoke?

 

http://www.rockymountainsusp.com/SlipYoke.htm bottom left

 

Is it a fast sharp vibration or a slow soft vib?

 

I'd check those U-joints first.