First of all, thanks in advance for your expertise.

I have searched but can't find anything specific to my problem

I had a shop swap my 410s to 488s. Takeoff is much better but there is now trumendous vibration at 40mph. I am afraid to take it faster than this. The truck has 31 inch bf goodrich all terrains.

I'm taking the truck back to the shop on Monday but would like to hear some feedback.

A little further info on the truck:

1987 p/u 4wd
IFS.
NWOR master build
Richmond 488s
Carriage bearings were allegedly wrong size so I ordered the smaller ones. Then they finished the install and handed the truck to me.

Weird noises, creaks, squeaks, rattles, and vibration at 40mph. Have not driven it faster than 45.

Thanks.

 

I found the answer on a jeep forum. The drive shaft is out of balance.

 

Hmmmmmmmm.....did it vibrate like that before the gear swap??

Did the driveshaft get bolted back into the same spot on the flange on the diff?

 

is the driveshaft out of phase or out of balance? If there was no vibration before it might just be out of phase...

 

I had that same problem with a 4runner and a Jeep Grand Cherokee. In the 4Runner the universal joint had went out, easy to tell just go under the rig and shake the driveshaft near the rear axle and you can see the movement, and in the Cherokee when I did gearing they had installed it wrong and I had a hum and a vibration at higher speed, the shop went and re-aligned the gears and the problem went away. Hope this helps