Clunk in rear differential

Sierra20 · June 7, 2004

My 2002 GMC Sierra has a clunk when it shifts. I hear it whenever I shift from park to any of the other gears, and when it is automatically shifting going down the road. It seems to be getting worse. I've checked the u-joints and they are tight. I am thinking its the rear end now. Anyone ever had a problem like this? What all needs to be replaced to fix this? A few mechanics have told me they think it is the spider gears that are worn and causing this. Any other ideas? How much would it cost?

citydriver · June 7, 2004

Weclcome to the Forum

Wish it was under better circumstances

Does your truck have 4wd? Could be the transfer case...

Is there excessive play in the pinion gear? Put it up on jackstands and turn the drive shaft by hand both ways to check for play or clunking with the tranny in NEUTRAL..this could also check the transfer case chain...

I havent done 1 in awhile,so I wouldnt guess at a price..BUT I would suggest several estimates from reputable shops in your area....GOOD LUCK

Sierra20 · June 7, 2004

Thanks for the info! It is 4 wheel drive. I had a mechanic look at it, and he claimed that the rear end is tight and thought it was in the transmission cause it sounds like it shifts in to reverse twice. I took it to a transmission shop and they checked it all out, hooked it up to the computer and whatnot, and they say my tranny is fine. They told me it is the rear end. I did ask them about the transfer case too. They didn't think it would be that. When driving in 2 wheel drive, they said the power is sent straight through the transfer case and its a solid connection inside there. Two shafts coupled together. They couldn't see how it could be the transfer case, but ya never know. Strange things happen. I did pull the drive line off and turned the yolk myself. I thought there was more play than normal.

citydriver · June 7, 2004

Do you have the button on the dash 4 the 4wd,or the lever on the floor?

I'm guessing mostly,but if you have the button on the dash,there may by an AUTO setting...in this case there is a differential in the transfer case also that splits power to both axles.I think...But if you want to check the rear axle,the best way I know is to take the cover off and drain the fluid to take a good look at the condition of the gear set,look for metal shavings or not....But someone else on this site may have more experience than I w/a '02....By the way,did you try your dealer yet? Just curious....

Cool Zr2 · June 7, 2004

u joints

Sierra20 · June 7, 2004

It's push button 4wd. I didn't check with my dealer. I don't have any warranty on it. Bought it as is. I am about 95% sure that it is the rear end though. You can kind of tell where the sound is coming from and it comes from the very back of the truck. I will have to take the cover off the diff. and check it that way.

Sierra20 · June 7, 2004

u-joints are solid. they have been checked

citydriver · June 7, 2004

You can kind of tell where the sound is coming from and it comes from the very back of the truck.

The driveshaft can almost act as an amplifier for sounds....Pull the cover on the diff. and take a look..only way I know to be sure..it'l only cost you a couple qts of lube,a gasket and a little time....

maroonsilverado · June 7, 2004

why would the spider gears be wore out on a 02? my dad had a similar problem in his 99. except his was when he turned. well finally one day the rear diff decided it had enough and spit pieces through the diff cover. left a hole in it about the size of your fist. but GM sent people down from michigan and they replaced it for free. and it would have normally cost about $3500. but he had a posi-trac w/ 3.73 gears, not sure what you're running though.

and i still wouldn't rule out the u-joints. if everything looks good in the rear end i'd replace those. dont cost very much and never hurts even if that isn't the problem

snoman · June 7, 2004

why would the spider gears be wore out on a 02? my dad had a similar problem in his 99. except his was when he turned. well finally one day the rear diff decided it had enough and spit pieces through the diff cover. left a hole in it about the size of your fist. but GM sent people down from michigan and they replaced it for free. and it would have normally cost about $3500. but he had a posi-trac w/ 3.73 gears, not sure what you're running though.

and i still wouldn't rule out the u-joints. if everything looks good in the rear end i'd replace those. dont cost very much and never hurts even if that isn't the problem

That just does not happen for no reason. Somebody had to really be extremely hard on that truck and is not coming clean.

Sierra20 · June 8, 2004

I took the driveline off and checked the u-joints so i could get a good feel for the joints. They both moved very smoothly. I'm running 3.73 gears. It isn't posi trac though. Have any idea what it would cost to replace the carrier, spider gears, and pinion shaft. Not including labor. My truck has 73k on it already, but it still seems odd to have rear diff. problems already. The guy that had it before me must have ran it pretty hard and spun the tires off of it.

maroonsilverado · June 8, 2004

well snoman, normally i would have agreed with you, but when GM sent thier technicians down they ruled that it was a defect in parts. they said there just wasn't really a possible way that driving the truck, no matter how rough, could do that. that's why they replaced it for free, and his truck had 45,000 miles on it.

and sierra, if you want a good guestimate i'd call the local chevy dealership, then that's going to be the extreme right there. if it were me, and i ruled that it was in fact the rear end, i'd get a whole axle out of a salvage yard and just replace it at home. then you dont have to worry about the spacing, etc. you just drop the old one and put the new one up. and a replacement rear axle will run you about $750 around here for a newer body style (99+). but that's a ball park figure

Sierra20 · June 9, 2004

I have considered changing the whole rear axle. I want to make sure what exactly is wrong in the rear end before doing that though. If the ring and pinion are ok, I'll probably just repair the rest of it. I've been told i could probably replace the spider gears, carrier, pinion shaft, seals, and bearing for around 400 dollars. Not sure how accurate this quote is, but the guy that said it has done this sort of work for 35 years. He also said that if the ring and pinion gears are messed up as well, it would be another 400 bucks or so.

Worktruck · June 9, 2004

Have a similar problem with my 02 Sierra 4.8 w/ 3.73 rear. Dealer has said that it is the slip yolk at the rear differential. There is a replacement nickel yolk but it is pricey and is not a warrantee fix. They also said there is no harm in driving it that way, so I am. BTW you hear it when you first hit the gas after shifting from park and any time you accelerate from a stop. Sounds just like play in the rear gears.

Sierra20 · June 10, 2004

Is yours getting any worse? Mine has seemed to get a little worse as time goes on. I hear it when shifting from park to any of the gears, when it automatically shifts up going down the road, or ya sometimes when i just hit the throttle from a stop. Mine sounds like it shifts twice when i put it in reverse. Its not, but makes two noises like it is. How much is that nickel yolk replacement? What is the difference between the stock and this one?

Do you or anyone else on here know anything about those Eaton LTD slip differentials? I see one advertised in a magazine for 367 dollars. Just wondering if you have to change the front differential or anything else to make this work.