vibration after 5" lift

[tiger9297]

I have a 2001 2500 and just installed a 5" lift and 37" Toyos. At slower speeds everything seems to be ok, but when I get up to about 65mph and over, I get a bad vibration which reverberates through the cab. I'm assuming this is a driveshaft issue with the change in driveline angles? Thoughts? Cure?

 

[Jeepwalker]

Could well be. Does it smooth out if you drop it in Neutral?

 

[tiger9297]

I didn't try that but it does seem to smooth out if I let off the accelerator. I guess that would be sort of the same. At first I thought it was a bad tire since the tires are brand new, but that told me it wasn't a tire. When the engine is "pulling" the vibration is bad.

 

[Jeepwalker]

That probably points to the driveshaft.

Have you ever spun a drive shaft by hand when the axle was at full droop (like if the frame was supported by jackstands)? Or, turned some other shaft with a u-joint at a sharp angle? If you have, what you might notice is a 'chugging' feeling as you slowly rotate the shaft. The reason is because as a u-joint cross joint comes around, the pinion speed decreases a little, then increases after the u-joint cross-shaft has passed. That is essentially what happens continuously when the driveline angle is changed too much and you are driving down the road.

There are ways to correct it, I'm not up on the most popular way to do it for Rams is ..maybe a CV joint?? On leaf sprung trucks you could just shim the rear end to lift the pinion a little.

 

[JB1]

What truck are we working on and what trans?....long bed, short bed, reg cab, crew cab?

 

[tiger9297]

My bad...Its a 2001 extended cab short bed. Auto trans.

 

[2001Ram1500SL]

I have had that same problem check both your wheel bearings if that doesn't work then check your tie rod ends first few problems if it gets worst check your idler arm

 

[dudeman2009]

Can you get a picture of the driveshaft from the side as the truck sits normally? Or an angle measurement (a smartphone app is good enough)?

There are three points to measure if you can.
1.slip yoke angle
2.driveshaft angle
3.companion flange/pinion input angle

You should have total working angles of less than 3 degrees between the front and rear U-joints or you'll get a pulsation as speed increases that is often described as a tire. If this vibration hits the right frequency the driveshaft will 'bounce' and make the whole truck feel like you have a dumbbell attached to the drive shaft.

The only real way to fix it is to reduce the total working angle (individual angles should be as small as possible but are less important than total working angle) by shimming the axle on the leaf packs, or replacing the U-joints with CV joints, but thats a custom driveshaft AFAIK