Rear end shudder/ vibration during acceleration after lift.

[Opeth]

Ok, this issue was not there before lifting and adding Z71 springs to the rear. Tires had no vibrations like this before everything which can rule out tire imbalance.

No vibrations can be felt in the steering wheel, I feel them in my butt and I can see my rear view mirror vibrate. This only happens on acceleration, I let off the gas/ neutral and vibrations stop no matter what speed.They seem to only occur in the 1800-2800 rpm range, anything higher and the vibrations are gone. No vibrations at highway speeds of any sort. If I do a slow acceleration, I don't get these vibrations which is leading me to believe its something drive line related. It's an extremely short wavelength vibration, like hitting a rumble strip, but not as harsh of vibration and no sounds.

I put my truck up in the air and inspected the u joints, there isn't really any play except the slop from turn the shaft on way to the other. All cups are intact and seem tight. However, the cups seem to be leaking grease and some looked like pretty fresh. I took some photos...

I took a couple more but they are blurry. Anyone else deal with an issue like this? Poking around on the web is pointing to u joints/ rear axle angle or carrier bearing angles ( we don't have these on the drive shaft like trucks).

 

[Darksidedown]

Mine does the same thing. Not sure what it is. Im going to just wait til it gets bad enough I can tell(it seems so slight no easy way to find it). Its been going on since Ive done the lift which was several months ago. If it explodes I suppose Ill know haha.

 

[gmcman]

Could have excessive angle on the joints? Coupled with alot of miles could be the culprit.

 

[tblazerdude]

Could have excessive angle on the joints? Coupled with alot of miles could be the culprit.

with just z71 springs? I dont think the 1.5'' lift would affect the joints that much. I could be wrong. I would check transfer case fluid and be concerned of the internals. Same for rear differential, more so if you have the G80.

 

[Opeth]

It's Z71's plus marks 2.5" spacer. Soo... More like 4" lift in the rear.

I'm pretty sure is the driveline angle change. When I get some free time and a non pouring day, I'll pull the drive shaft and rotate both joints to see if anything is binding.

 

[gmcman]

Ok, this issue was not there before lifting and adding Z71 springs to the rear.

When you lifted it, you were likely right on the cusp of noticing the vibration, the springs must have pushed the joints past that point.

I had an 81 Firebird once and installed some air shocks because with 4 people it almost dragged the ground. One day I had a bright idea and loaded the shocks up with about 100 psi and took it around the block....I thought the driveshaft was going to come out.

 

[tblazerdude]

Why would it happen only during initial acceleration and then go away?

 

[Opeth]

Initial pressure on the joint/ torque to get the truck to move, once the truck is rolling it doesn't require a much stress on the joint. Also the driveline angle changes slightly when the vehicle is moving. You see cars squat when the begin to move, weight shift.