[sharpshooter]

I have an 04 Silverado 5.3 crewcab 4x4. Bought it with 60,000 miles on it and it has had the notorious slip yolk clunk since I've had it. I'm now at 130,000 miles and it has this sporadic knocking/clunking coming from the rear end. It does it mostly while easing off the throttle or just giving enough throttle to hold your speed, but will also do it under acceleration. It has yet to do it in the morning on the 10-12 mile drive to work but mostly does it about half way home in the afternoon. It may knock once or be a rapid series of 4-6 knocks when it starts, then it will keep doing it off and on till I get home. I had the truck in a shop for a week and they heard the noise on the road but couldn't replicate it on the rack. They changed the transfer case fluid and said it looked good, u-joints and driveshaft are good and changed the rear differential fluid and said it looked ok, no metal in any fluids. Their thought was the G80 locker may be the problem. Since they couldn't get it to replicate on the rack and pinpoint the noise and since the fluids and rear end looked good they told me to come and get it so I wasn't out of my truck any longer. I also didn't want to throw money at something without knowing for sure it was going to fix it. Have any of y'all had a problem like this or can you tell me something else it may be?

 

[Differently]

Any decent shop should have some chassis ears. They Have multiple alligator clip pick ups that you attach to any suspect area, then while your test driving you can cycle between them to pinpoint the problematic area.

 

[j cat]

my 2000 had this clunk BUT only when at a stop like a traffic light when taking off .. that was the yoke .. 30K miles warranty dealership replaced the transfer case fluid tracII GM fluid blue. problems ended .. so after that I do all the drive train fluids 40K miles .

you problem may indeed be a bad U joint. to check these out esp with the big aluminum drive shaft if must be removed and the joints inspected for wear and in my case one was seized. this cause all sorts of noise ..when you put the drive shaft back in use moly grease on the yoke .

rear diff cover must be removed and the box inspected and cleaned ... possible if the diff cover was never removed and cleaned the locker could be with damage . 75-90wt synthetic gear oil only......

 

[tac]

"they said". imagine how hard it is to describe a situation you know is not right and expect someone else to chime in to what you are hearing. all good just think. like advice out of your own mouth. may the wind be at your back.

 

[Zach Smith]

I'm with different's chassis ears. Other than that, it really does sound like a u joint, clunks on speed change...needs a little resistance and heat to get it going though. Did they try "power braking" while on the lift, then slowly releasing brakes and free roll. Then another time but slowly re applying brakes...all after warm and driven? A two man job for sure with a lift and steth. Or some jack stands...you and a buddy could do the same thing. One silly question, have you cycled the 4x? Does this happen in 4H?

 

[sharpshooter]

Don't know if they power braked or not. I cycled through 4wd in the driveway but not on the road. If it starts doing it again this afternoon I will put it in 4hi and see what it does.

 

[j cat]

"they said". imagine how hard it is to describe a situation you know is not right and expect someone else to chime in to what you are hearing. all good just think. like advice out of your own mouth. may the wind be at your back.

this member appears to be second guessing the answer to his issues with the repair shop .. most times shops just throw parts at it and guess at the owners expense. If he does not check the drive shaft then it will be an expensive fix...

 

[xPosTech]

I would start by spraying all rear suspension points with WD40 before your drive home. Any place at all that moves including the length of the springs, eyes, shackles, u-bolts, swaybar mounts and end links, etc. There's no single suspension part that I would suspect over any other but you will either prove or disprove it's a suspension part that's making the noise.

It wouldn't take 10 minutes to get every thing drippy with WD40. It would be very temporary so if it did eliminate the sound it would be back in less than a week and then you could spray just certain areas to narrow it down. If it did nothing to the clunk/knock it didn't cost much to do. You could then concentrate on other areas.

Ted

 

[j cat]

when I had the clunk 16 yrs ago I used 5-56 power lube on the yoke .. clunk disappeared for a day or two then came back ..

my 2016 toyota truck does have grease fittings for the yoke and all the U joints..

 

[xPosTech]

AHA!!! I knew if you kept talking about that Toyota you would eventually let slip a design defect!!! Everybody knows that u-joints without zerk fittings are stronger than ones with the fittings!!!

Ted

 

[Zach Smith]

AHA!!! I knew if you kept talking about that Toyota you would eventually let slip a design defect!!! Everybody knows that u-joints without zerk fittings are stronger than ones with the fittings!!!

Ted

Ha!

 

[j cat]

AHA!!! I knew if you kept talking about that Toyota you would eventually let slip a design defect!!! Everybody knows that u-joints without zerk fittings are stronger than ones with the fittings!!!

Ted

the 2000 GM truck now has grease fittings . sure those holes do make the portion that supports the drive shaft weaker but I never seen the U joint break due to the metal support of the bearings. the bearings require lube in the rust belt .. probably not in a warm climate...

the U joints and yoke lube is a good way to keep them working properly .. another thing the GM truck , has aluminum drive shaft which in rust belt does require some to get new drive shaft due to corrosion .. toyota has all steel no aluminum..

my boat has on the lower unit U joints and these are lubed every boating season they are now 37 yrs old .. just checked them out ready for the cold winter to arrive...

what I find weird is GM has the most awards on the vehicles they produce ..

Toyota has the highest reliability of all vehicles .. GM not in the top 10 on reliability ..

That is why after 50 yrs no GM vehicles .. they break easy esp those wiring/electrical failures ..

 

[sharpshooter]

Ok, since my last post I have sprayed the suspension components as best I could, noise still there. I engaged 4hi when it started and it had no effect on the noise. I had both u-joints changed and that did no good either. Next step is to put it in a different shop and see what they find. Looks like the money is about to disappear.

 

[Zach Smith]

Ok, since my last post I have sprayed the suspension components as best I could, noise still there. I engaged 4hi when it started and it had no effect on the noise. I had both u-joints changed and that did no good either. Next step is to put it in a different shop and see what they find. Looks like the money is about to disappear.

I know its a bit late here, but how about body mounts...or something Rolling in chassis, a rock...socket...something hidden somewhere, tail gate...I know it doesn't make much sense for only happening when warm but, maybe that's a coincidence, or there is an alternative explanation, like inertia...just figure its worth a shot, before you empty your wallet on it...if not, try to make sure you find a shop that has and can use a set of ears...at least they can narrow the area of the problem more efficiently.

 

[j cat]

on forums noise is very difficult to help people ... you have had a shop try to find problem and they could not help...

replacing fluids in the drive train is NOT a wasteful expense.. since YOU are not the person working on the vehicle this can be expensive having others do the fix. a vehicle this old sure could be a body integrity issue..

GM uses a wax like coating on the frame this coating hides the metal corrosion .. I every spring and fall check for this GM coating issue . then as it lifts off the metal , I scrape off the GM crap and apply a mineral based black coating to seal the steel.

so several years ago despite my inspection and work I had to have a metal tube cross member replaced . this held the rear of gas tank .
lucky for me it cost $400 to have a shop that did many of these, and they did a good job... they fabricated the tube since GM does not have this part as it is part of the full frame ..

when I first noticed this corrosion I only saw a slight 3 inch crack because of the coating.. as I scraped off this GM crap it was over a foot long and 1-2 inches wide lucky the gas tank did not fall out..

 

[sharpshooter]

Ok answer me this, when it starts clunking/knocking and I ease on the parking brake, maybe 1/4 of the way down, the noise goes away. Talked with the guy, who is supposed to work on it Monday, and without him hearing it yet he still says it's the G80 locker. Parking brake problem or rear end problem?

 

[Zach Smith]

Ok answer me this, when it starts clunking/knocking and I ease on the parking brake, maybe 1/4 of the way down, the noise goes away. Talked with the guy, who is supposed to work on it Monday, and without him hearing it yet he still says it's the G80 locker. Parking brake problem or rear end problem?

I don't know bud, for me that's a little like saying a watermelon is blue on the inside till you cut it open and then it turns red, go ahead and prove me wrong. maybe somebody else will want to weigh in though. Its possible either way from this side of the net without seeing, hearing...

 

[sharpshooter]

I hear ya, just trying not to get taken to the cleaners.

 

[lemitar]

What happened with this?, sorry to revive a dead-thread