99 Suburban 2500 Help

[Ryno3]

I had a 1999 Yukon do this recently, if placed in 4HI the vibration/noise would go away. The output bearing had failed in the Transfer case.

 

[1998_K1500_Sub]

The weights on the driveshaft are still in place, verified when I changed u-joints. I have been considering getting the shaft balanced.

Sorry if this has been answered, but...

Is there any chance the driveshaft is mildly bent from some unknown prior trauma? Can you put it on jacks and set a dial caliper against the shaft and turn it to check?

Although this doesn't jibe with the "it vibrates worse when trailering, etc." but we're all still grasping...

@Ryno3's post is intriguing.

If you can't sort this problem out, I think you should just sell the truck... and I'm willing to find you a buyer

 

[Nad_Yvalhosert]

If you have a flat & level surface, lift the beast up on jack stands. Remove the wheels and drive it in tbe air. (Throw a couple lug nuts on to hold the drums) Do this both in 2wd and 4x4. See if you can recreate the vibration.
Usually... high speed vibration is associated with tire imbalance. Considering you already ruled that out by swapping different ones, you're on to step 2 of vibration diagnosis.

 

[1998_K1500_Sub]

If you have a flat & level surface, lift the beast up on jack stands. Remove the wheels and drive it in tbe air.

I like @Nad_Yvalhosert’s approach and have used it myself but, if you use it, keep in mind that the jack stands, being rigid points of connection to the ground, may also minimize the vibration of whatever they’re in direct contact with (e.g., the rear axle, frame, LCAs…).

Suggestion: Choose the jack stands’ placement thoughtfully and / or try the same experiment repeatedly, with the jack stands placed differently each time.

 

[Chad_MT]

Thanks guys, I'll throw it up on jack stands and give that a go. Hopefully with no load it will still do it. Also going to thoroughly inspect the transfer case. That would really be the preferred problem if the output bushing is bad, it needs to come apart and have the pump rub fix done anyway.

 

[thebigcar]

Thanks guys, I'll throw it up on jack stands and give that a go. Hopefully with no load it will still do it. Also going to thoroughly inspect the transfer case. That would really be the preferred problem if the output bushing is bad, it needs to come apart and have the pump rub fix done anyway.

With a vehicle as old as yours, expect to replace almost EVERYTHING - I'd start by putting new motor mounts and tranny mounts in it - the vehicle is over 20 years old and the rubber should be shot by now. I've also seen on youtube that the front driveshaft slip yoke seizes on the output shaft of the transfer case causing bad vibrations. You'll have to beat the yoke off then clean off the rust and lube.

 

[perfect777]

Had a similar issue - 99 K2500 Suburban (lifted on 35's). I was convinced it was the tires. One day I randomly decided to replace the crusty suspension shocks with some high quality Bosch shocks. The problem immediately went away. The old shocks had virtually no rebound - so the front end was just bouncing around at high speeds. Scary! Maybe take off your shocks and confirm that they have solid compression/rebound?

 

[Opie-joe]

Check your rear drums. New drums for these trucks are crap. I went through 8 pair and 3 different brands/suppliers before I found decent ones. Pull them off and check that they are concentric, not out of round and/or “bell mouthed”.

 

[Chad_MT]

@perfect777 I thought the same thing, but it has Bilstein shocks on it from the PO. I'm going to check them when I swap out my winter tires to make sure they are still good.

 

[Chad_MT]

Check your rear drums. New drums for these trucks are crap. I went through 8 pair and 3 different brands/suppliers before I found decent ones. Pull them off and check that they are concentric, not out of round and/or “bell mouthed”.

I also thought drums and replaced them, no change, exact same symptoms.