New member from NY State w/2002

[Semperfi_ny]

Hello. Bought a used 2002 GMC Sierra 1500 SL Ext Cab Stepside with 4.8L V8 last week. Owner of the shop advised that they had the pinion bearing replaced as well as tie rods. Said if I feel vibration it should go away. I noticed at deceleration, under 30 MPH, I get a howl and slight whine. I decided to test drive it and closed the deal. I took it to a shop I'm familiar with and they said pinion bearings are bad without taking it apart. Called the seller and they said there's no way thats it but to bring it back and they'll check it out. Could it be the bearing in the yoke area (think that's whats its called)? Or as the video describes, the preload came loose somehow. See the video I found, this is exactly what happens. 

 

 

Yesterday, I crawled underneath. Nothing is loose, thinking it was driveshaft or u-bolts. Noticed I have 2 piece driveshaft. Carrier bearing in the middle looks new. Bolts are still steel colored

 

Any help would be appreciated.

 

Also feel a thunk sometimes under my feet while driving and decelerating.

Edited April 18, 2022 by Semperfi_ny
Additional info

[richard wysong]

if they did the pinion bearings it sounds like they screwed up the the pinion depth to the ring gear or the preload is wrong. if you read the procedure to properly set up a ring and pinion it is very complex and requires special tools. DO NOT drive it until it's fixed or you will permanently damage the ring and pinion gears. properly set up it should be almost silent. you may have to take it to a specialist if they say it will go away if you drive it, it will only get worse. to do the pinion bearings they would have had to remove the ring gear carrier and they may have mixed the shims up so now you have to do the whole set up procedure

[richard wysong]

it's also possible that the ring and pinion were permanently damaged before they changed bad bearings which may have caused a leak at the pinion seal resulting in worn gears. if the gears are damaged no amount of adjusting will quiet it down

[richard wysong]

It's very unusual for pinion bearings to fail as they are submerged in gear lube so maybe it was never correctly diagnosed. Years ago I ran into a k1500 that someone had worked on and had installed the carrier shims on the wrong sides. Switching sides cured the noise

[Semperfi_ny]

Took back to the place I bought it. They are going to tear the rear end apart. Funny, when I dropped it off, the sales associate (she has no clue what vehicle has what in it) said "they fixed a pinion seal leak and the owner was hoping that was going to fix it." I told her once it's done, I'm going to drive it to ensure it was done right and have my mechanic look at it again. She reiterated that it will be done right.

Thanks for the assistance!

[richard wysong]

 sounds like they ran it out of oil damaging the gears.  hope it turns out well for you

[Semperfi_ny]

Possibly...Hopefully not. Either way, they're fixing it all no cost. 

[Semperfi_ny]

Well all fixed. Got it back at the end of April. No issues, drives super smooth. Zero noises. They had to put a new rear end in the truck.