Hello. Vehicle in question is a 2007 GMC Yukon XL 4x4 5.3

I recently did work on my truck and now there’* a terrible vibration (not to be confused with a shake) at about 72mph-77mph. Outside of that range, it drives fine.

The work I did... replaced u-joints. While drive shaft was out I replaced rear seal on transfer case. During the process of replacing seal, I noticed transfer case fluid was black so I drained and filled with new transfer case fluid. Replaced front right half shaft. This is all the work I did between the ‘before & after’ of the vibration.

Any feedback would great. Thanks for reading.

Balance the tires. You may have lost a wheel wight.

Thanks for the reply. Wouldn’t the balance be an issue at anything over 77 mph as well? As soon as I hit about 78mph, vibration is gone. Anything below 72mph... no vibration. And it’* a pretty bad vibration that rattles every loose thing in my truck.

Can you tell if its coming from the front or rear?

Definitely feels like mid to rear of vehicle. But the entire vehicle vibrates. But it’* much louder in the back of the truck.

Then I would suspect one of the u-joints you replaced. Verify that they are seated all the way and that there is no excessive play in them.

Make sure you used correct fluid. Only use manufacturer recommended fluid. Had several times where wrong fluid was installed causing damage. But it really sounds like one of the U-joints like Mike stated above, Make sure none of those needle bearings popped out when you were installing the bearing, it can get caught at bottom of bearing cap.

Did the U-joint slip into the differential yoke easily? Some of these have a narrow yoke on the differential side, so the caps need to be squeezed in a little extra to install. This will put the centering at the mercy of the seals, and it will often end up a little off.