clunk in rear end

I have a 97 and when I push on the gas pedal at low speeds it has a clunk noise. I am thinking that its a U-joint type of thing but I am not sure. Does anyone know where this might be coming from?

Take the drive shaft out and see if the ujoints are in good shape to rule those out. Otherwards, put vehicle in nuetral and grab the driveshaft at the companion flange and try to rotate it. If it moves half an inch I might worry. Some play is normal. Also, it isn't unusual for a rear wheel drive vehicle to have a slight clunk in that situation. My 97 silverado with 140k did it and so does my 03 with 40k.

ok well I am not sure what the flange is but I grabed the shaft right in the middle and it will rotate about 1/2 inch but it has a clunk in it just like what I was hearing. is this good or bad?

Half inch sounds like a bit much to me. I think mine may turn 1/16 to 1/4, but def not half. If it was me, I'd keep an eye on it for a while and just wait, but it may strand you if you do that.

that tells me you need new u-joints

so that is what is wrong with it? when you can turn the Drive shaft that much it means that the u-joints are bad?

yep. The u-joints are worn down and Need to replace them.

Well I am no Machanic by any means, So I thought that my Drive shaft needed to be replaced. so U-joints are only about $125 to get fixed.

Well I am no Machanic by any means, So I thought that my Drive shaft needed to be replaced. so U-joints are only about $125 to get fixed.

The only time you would need to replace your DS is if it was bent, or is the adjuster is shot. otherwise, it would be the u-joints that connects to the DS.

how hard would it be to fix them myself? I was told that you just have to remove the 4 nuts on each and they just drop right out. is that true?

here is another thought. Could it be the gears in the rear end? Just a though.

Four bolts hold the drive shaft in but I doubt they have that much play in them even if they are bad. Usually when a U-joint is bad they cause a vibration or a noise. If they were bad enough to cause excessive play then you could look at the U-joint while you move the drive shaft and you would be able to see the play in the joint itself. If the driveshaft moves but the companion flange or slip yoke doesn't, then they are definitely bad. The clunk is probably in the rear end because of too much backlash caused by worn out gears.
It goes transfer case...slip yoke...u-joint...driveshaft...u-joint...companion flange...rear end
If that helps with terminology.

ok so I think that it is the pinion and ring. but would the spiders be bad as well.

Well, they may not be bad. I said worn out gears in my previous post but I meant just worn gears. When rear ends are set up they are set with some backlash, or play in the ring and pinion gears to allow for heat expansion and lubrication....If you know a lot about rear ends you could tear into it and roll a tooth pattern and measure backlash to see what needs to be done but that takes some special tools and can be a pain when dealing with shims.

As long as you only have some play by rotating the driveshaft and don't have any side to side or up and down movement of the companion flange I might not worry too much about it. Every GM 10 bolt I've ever had has clunked.

Well I have only had the truck for 4 days now and It didnt clunk for the day and a half that I test drove it. So I called the Chevy dealership where I got it from and they are going to look at it for me for free and tell me what is going on. All I know is that this has got me Stressed out when you pay 10K for a truck and it might be junk.

if you want junk, buy a ford.

I watch this forum all the time, as well as the cutlass forum (guess what vehicles i have).. and I've never posted. This however, got my attention.

I picked up a 2000 silverado in february. 4x4,ext cab, long box, with a 5.3. After a month or so I developed a clunk. It was on acceleration, and AFTER braking. Kinda felt like universals, but that was easy enough to check. I too thought rear end gears. I took it to a few places, and noone could help me. I talked to a lot of people, and read a hell of a lot on the internet, but couldnt find help. It was quite a solid clunk, but I couldnt find it.

It turned out to be the slip yoke on the driveshaft. Mine is an extended wheelbase, so I've got the 2 piece driveshaft, with hanger bearing. Right behind that hanger is a boot, and inside is a slip yoke, which allows the driveshaft to "shorten and lengthen" when required by movement of rearend, suspension, etc. Took it apart, cleaned it up, and put in some "Red 'n' Tacky" grease. Just a canadian tire grease that I've had good experience with. Just filled the splines and put it back together, put the boot back on. Ta Da.. . .the clunk was gone.

What MY clunk was, was the slip yoke failing to slip. Basically, there was no grease left on it, so it would bind, until the force got so great, that it "popped" as it moved.

This may or may not be your problem, but It's one that I had trouble finding.

Basically, it would clunk just after you started moving, and just after you stopped. If I used the brakes to come almost to a stop, and let off the brakes, it would also clunk. Most noticeable though, was the clunk just after you got on the gas. Even if I was light on the gas, it would clunk, about 5 feet after starting to move.

Like I said, mine is an EWB, so your slip yoke would be where your shaft enters the transmission. I dont know if this is a problem there or not, but It sure was for me. Just my 2 cents. Hope it helps. Let Me know if it does.

That's funny, now I remember one of my old instructors who was a GM tech had said something about that on suburbans. Another place to look.

Well there is just so much play in the DS that I donsnt seem like that could be it. but I will look I guess that I am just looking to see if there is any lube on the yoke that insers into the trans.?

Mine has a pile of play in the driveshaft as well, in that it can rotate a lot. Almost feels like somethings worn in the drivetrain, i know what you mean. But thats where my clunk was coming form. You'll have to take the two pieces off the companion flange, that hold the u-joint in. It'll just be 4 bolts, i believe with 14mm heads. (not sure on that). Then you can knock the driveshaft off that end, and pull it down and back, out of the transfer case. Clean up that spline with some brake cleaner and the like, and grease it up good, slide 'er back in and pop the pieces back on the flange with the u-joint in, and try her out.

I believe GM makes a product just for this purpose, they call it yoke grease I believe, used to have p/n for it. But its like 4 oz for somethin along the lines of $30. I bought a normal size tube of that "Red 'n' Tacky" for $6. I've got 15k or so on mine so far, and the clunk hasnt come back. Its a heavy equipment grade grease, and it's just like it sounds, bright red, and real tacky. Apparently stays put better, in roatating mass such as this application. I'd say give it a shot.

ok well that sounds good to me. I was under my truck like every night trying to figure this out. well post #20 kind of makes sence to me since it seems alot more loose in the front of the DS than the Back by the Dif. Does anyone have anything to say about this?

Thats where my play seems to be as well, inside the transfercase. you can actually hear it if you listen closely, it seems to be "bringing up" inside there. Gee... sure hope this works out for you. All of a sudden it seems like it might be worth posting.

Well I got the Dealership to open up the rear end today and have a look see. So I am going to be taking the truck in so we will hear the final result later on today.

ok well I just got back from the Dealership and they took everyhting that they could think of apart and they said that it all checked out fine. its just one of those things that are natural. they did say that my Leaf springs were Loose? so they put somthing rubber thing in there to make it tighten up. they said that that might be some of the noise I heard.
Thanks for all your help.

That leaf spring thing, they call it rear end slap. Did the same thing for me. Did nothing. Thats basically a small noise you hear when the rear end rotates forward and back ,and the overload spring hits the regular spring. Theres little rubber blocks there fomr the factory, but they wear out. If your problem doesnt go away, definately take the driveshaft out and grease the yoke. Soudns exactly like my problem. For 15 minutes work, its definately worth a shot.

Evan

So I just need to grease the yoke at the Tans. end? not to bother with the rear?

ok so what is the trick to get the DS to drop out after you take out the 4 bolts?

ok so finally got it out and used the "red and Tacky" on the spline (I hope) but I could only see about 1.5- 2" of is so thats all I got on there didnt really take too much. So I got it all back together and took it around the block and it didnt clunk so I am going to go get my wife across town and see how it really does.

hmm. .you shuld have been able to give the universal a crack or two and pop it right out of the carrier it it sits in, such that it can drop down, then you can slide the driveshaft back, right out of the transfer case. That way, you can grease the whole spline. I packed mine right full of greas,e level with the teeth. Slid it back together and presto. Good luck with it, hopefully you got enough on it to stop it from binding. Let us know.

ok well I got the shaft out. however there is a rubber boot that is connected transfer case and I couldnt get it off to get to the whole spline. I did think about taking the tube of grease and sliding it over the spline and that would give it a good coat of grease? what do you think? anyhow it only poped once while drving around town.

Hmm. . .obviously I dont have a good mental pic of your setup, and the manual I have doesnt illustrate it as well. I thought it was like my old rig, where the driveshaft just slid into the transfer case, and the rear had the universal/companion flange setup. Obviously this isnt the case. However, all I can tell you is to try to grease that spline all the way. If thers room to slide the tube in, perhaps there's room to slap some grease on a paint stick, and pop it in through the hole? However if it only popped once, I assume it was much worse before (at least mine was) and hopefully we're on teh right track. My boot was removed before I got the truck, and is now held on with just two pipe clamps (on on each end). It doesnt affect the balance from what I can tell. Good luck with it.

Evansamms is right. I have had numerous 99 & newer silverados. 99 percent of the clunks coming fron the rear (or that is what you think it is, the noise travels to the rear) is fron the slip yolk. I have replaced several with the new nickle plated ones & the noise does go away. Have the dealer check that.

So are you saying that if I get a nickel plated slip yoke that should stop the clunk? it is about to drive me up the wall

I have more than a clunk going on in my rearend... I am not a mechanic can anybody help me figure out what it is.. It is more of a popping noice constanly and slipping too.. Is it the rearend or the transmission.. Mine is a 4+4 z71..

It is mostly likely the rearend. Does it pop when you make turns?
Does it shake the entire truck when it pops?

It pops constantly.. It started out when I would acclerate but now it does it all the time. Im not driving it anymore it feels like something is about to fall out from under it. And yes it shakes the whole truck. So exactly what part do I need to look for?

It only shakes when it pops? Is the noise really loud, like a gunshot in the truck? Does it scare the crap out of you everytime it pops? If that is what you are hearing then you will need a new Rearend. Go to http://www.jasperengines.com/

If what you are hearing more of an annoyance than it sounds like a slip yoke.