Vibration at higway speed with lift?

[kevinhaeb]

I recently did a lift to my 99 D1, three inches total suspension. It is perfect up until about 55 mph. After that, whenever I start to barely give it gas or just before it reaches the floor letting off the gas, the truck starts to vibrate underneath. My guess is one of the driveshaft. If I give it constant gas or completely let off, it won't do it. So, it's only when the pedal is about an inch from the resting position either way. I don't care about the vibration, I just worry that it may lead to problems down the road. Put in your 2 cents.

 

[koby]

it's your POS rack...

 

[Mike_Rupp]

Do you have a rotoflex rear shaft? They don't work well with lifts.

Assuming you don't have a rotoflex, my guess is the front driveshaft. Take the front shaft off, lock the cdl, and drive it in the same conditions that made it vibrate before. If it doesn't vibrate, you'll have to venture down the road of: new double cardan front shaft and possibly new front links to correct pinion angle.

 

[Rikstaboogie]

still got problems?
check your "uj's".