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Clunking coming from rear

This is a discussion on Clunking coming from rear within the Drivetrain forums, part of the LSx Technical Help Section category; I've got a problem with my '02 Trans Am. On my way to a friend's house, I started hearing a ...

  1. #1
    Member jcws6's Avatar
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    Question Clunking coming from rear

    I've got a problem with my '02 Trans Am. On my way to a friend's house, I started hearing a light clunking noise from the rear end. As I was driving back, it began to get louder, and it happens every time I drive.

    The clunking seems to be coming from the rear end of the car, and it's speed-dependent (i.e. increases in frequency as the car speeds up). Happens in all gears, but is MUCH quieter when I'm coasting in neutral. I took the car to a transmission shop, and after a test drive & checking it on a lift, the guy said I needed a new rear U-joint.

    So, today I got the car up in the air & replaced the u-joint with a brand new greasable one from Summit Racing. While it was off the ground, I spun the tires to see if I could hear the noise, but there was no noise. I also checked the gear oil level in the rear end - it was normal.

    After the repair, I took it for a test drive. Same noise! The car's a 6-speed, hasn't really been driven that hard, and under 25,000 miles. Any suggestions on what the noise might be??

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    69 hugger orange
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    having the exact same problem after a run at the track
    i replaced u-joints, wheel bearings, and completely pulled my rear end apart to inspect for damage, nothing noticeable so i took it to a shop and all they could tell me is you have internal rear end noise and there is nothing we can do without just replacing everything until its fixed
    they think i torqued my housing a little which has distorted the gears contact area
    needles to say dont waste your money fixing your 10 bolt
    im ordering my 9" monday
    oh yeah and i also took my driveshaft to make sure it wasnt out of whack and it wasnt
    car still makes the noise but i have been driving her anyway
    if you cant afford a new rear you could start replacing and hope for the best,but there is always a chance you put all new stuff and still isnt fixed

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    69 hugger orange
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    did you check all your bushings also,tranny,control arms ,torque arm and anything else that has a bushing

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    Junior Member jeffstaples's Avatar
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    Did you check the two bolts holding your torque arm to the rear end housing? They may be a little loose causing the clunking.

    Jeff

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    Member jcws6's Avatar
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    I didn't check the bushings or anything else yet. Any specifics I should look for?

    I DID check the torque arm though, because I was thinking of removing it for more clearance when I took the driveshaft out.

    Thanks for the suggestions, guys. Keep 'em rolling in! I wasn't really planning on springing for a new rear axle this soon...

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    LS1 chosen son lemons12's Avatar
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    traction cont. check your tires and make sure there is no bulge. might have torn a belt. ujoint woulda been my first guess... bushings and stuff.. gears?? but doubt that one..

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    Quote Originally Posted by jcws6 View Post
    I've got a problem with my '02 Trans Am. On my way to a friend's house, I started hearing a light clunking noise from the rear end. As I was driving back, it began to get louder, and it happens every time I drive.

    The clunking seems to be coming from the rear end of the car, and it's speed-dependent (i.e. increases in frequency as the car speeds up). Happens in all gears, but is MUCH quieter when I'm coasting in neutral. I took the car to a transmission shop, and after a test drive & checking it on a lift, the guy said I needed a new rear U-joint.

    So, today I got the car up in the air & replaced the u-joint with a brand new greasable one from Summit Racing. While it was off the ground, I spun the tires to see if I could hear the noise, but there was no noise. I also checked the gear oil level in the rear end - it was normal.

    After the repair, I took it for a test drive. Same noise! The car's a 6-speed, hasn't really been driven that hard, and under 25,000 miles. Any suggestions on what the noise might be??
    i have an 02 ss camaro and i had a similar nouse ended up being tranny mount changed it out for poly one from energy suspension it is actually the u joints hitting floor board of car on my car check it out see if it helps. if not check rear diff.

  8. #8
    Member jcws6's Avatar
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    Well, it's definitely not tires - my Goodyear Eagles are about 3 weeks old now. I still heard the noise before I got the tires, but I was due for a new set anyway. When my car was on the lift, I asked the mechanics to check the noise out. They said they wouldn't be able to pinpoint the cause without a more invasive inspection + a "diagnostic charge." Yeah, screw that.

    I struck out at NAPA, Auto Zone, and Advance Auto last night looking for the Energy Suspension transmission mount. I did some research, and it looks like that's the one for me. I called another Auto Zone today, and the guy said they have one left in stock (3.1108G, right?). So, I'm hoping to pick it up today and install this weekend.

    The transmission mount installation looks pretty straightforward, so I should be all set with that, thanks to InstallUniversity. If the transmission mount doesn't work, is there anything else I should check while I'm under there?
    Last edited by jcws6; 04-24-2008 at 09:14 AM.

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    I took the transmission mount off today & it looked fine. Since I bought the Energy Suspension mount already, I put it on anyway. While the car was in the air I started it up, put it in gear, and gave it a tiny bit of gas just to turn the rear wheels a bit. I could very faintly still hear the noise. When I put the car back on the ground & gave it a test drive, the noise was still there, just the same as before.

    I was going to drain the carrier & look at the gears, but I noticed the previous owner put on a custom differential cover from Summit. It had some strange lookin star-shaped bolts on it, so I wasn't sure if I had the tool to take them off.

    With a car under 25,000 miles, I'd think it would be unlikely to have gear trouble, but I guess anything's possible. I'd really like to get my car back on the road, so... any other ideas, guys?

  10. #10
    Junior Member WS6 T/A's Avatar
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    I was having the same sounding problem on my 00 ws6. I was going crazy trying to figure the problem out. I put a new energy suspension tranny mount in today and the problem was still there. U joints were tight. So I checked the rear differential fluid and it was clean. I decided to pull the cover off anyways. The gears turned out to be the problem. The pinion gear was missing a huge chunk out of it along with many other broken teeth. I'm not sure if thats your problem but I figured I'd share my story.

  11. #11
    Member whiteLS1TA's Avatar
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    same thing happing to me on happens when i power shift into second. today i was getting on the freeway, i was in third and shifted down to second and gunned it and it felt like my rear end was loose. but made that clunking sound. so ima change u joints and replace tranny mount hopefully thats th problem. also my right rear tire has about 905 tread and the left rear tire has about 30% tread, that might be the problem too.
    i also did do a lot of donuts and burn outs so that might be my prob

  12. #12
    Member jcws6's Avatar
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    Well, crap. I was afraid of a rear end problem, but I'm running out of stuff to check/replace. It's complete BS that a differential assembly would die this soon. So far, I'm 0 for 3 now on GM 10-bolt rear ends, so I'm definitely leaning towards a complete rear axle swap. I suppose it could still be wheel bearings, but is it worth checking those?

    This weekend, I'll probably drain the pumpkin & look at the gears (weather permitting). It looks like this is the cover on my car: http://store.summitracing.com/partde...5&autoview=sku, and I'm hoping the custom bolts will come off with a 12-point socket.

    Any advice on what I should be looking for (besides a big chunk missing from a gear) would be appreciated.

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    I would check the control arm bushings and all the mounting hardware if you've already replaced it twice before. Could be a loose mounting bolt like I've seen before.
    TSP 347 SB, TSP Stage 2.5 PRC LS6, TSP MS4, Performabuilt Stage 2 4L60E, Yank PT4000, 4.11s, Fast 90/90, FTRA Cold air intake+all the free mods, Dynatech Supermaxx Exaust System, DMH Cutouts, Hooker Catback/FTRA Tips. Tuned by RPM/Garner NC. 11.28@119

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    Member jcws6's Avatar
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    Thanks for the advice. I've never replaced the rear end on this car, but I did on two other cars (a '90 formula and a '96 GMC Jimmy). I actually rebuilt the rear end on the Jimmy myself, only to have it fail again around 30,000 miles later, but that's another story.

    I'll cross my fingers and take a look at the bushings & junk this weekend, if I can. Everything looked pretty tight back there last time, but I'm hoping I missed something.

  15. #15
    Member whiteLS1TA's Avatar
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    well i had the same problem swapped out the u joints and the clunking went away!

  16. #16
    Member jcws6's Avatar
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    I took the car to the same transmission shop again today. The guy put it on a lift and put it in 2nd, so the driveshaft was spinning. He called me back to take a look, and it "sounds" like the noise is coming from around where the driveshaft meets the pinion yoke. He said the cardboard liner on the inside of my stock aluminum driveshaft came loose and is rattling around inside the driveshaft. He even called a rear end/drivetrain shop to verify his theory. He said if it was gear noise, he would've known right away.

    So, I took the car home & pulled the driveshaft out. Again. While I was under there, I checked the rear LCAs, the panhard rod, sway bar clamps/endlinks, and the lower shock mounts. I checked the parts by wiggling them side to side with two hands (fairly hard), then banging on the middle of the part with my fist to listen for any noise. Nothing budged or made a sound.

    After I got the driveshaft out, I shook it pretty hard while holding the u-joints. Both side-to-side and up & down. No noise at all. Nothing. The diagnosis was made by the owner of the shop, who's been pretty good in the past. A while ago, the same dude correctly diagnosed a rear end problem in an old GMC Jimmy I had, based on the test drive alone (a mechanic at another shop had the truck on the lift & couldn't figure it out). But now, it looks like the guy is 0 for 2 on this one.

    What do you guys think? Am I missing something? This problem is starting to drive me F'n nuts!

  17. #17
    Junior Member IIquick66's Avatar
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    I just bought a 99 SS m6. I put it up on the lift to try and track down all of my noises. So far I've found the the exhaust after the Y is hitting the cross member and the control arms have some play in them. When I grab them and give 'em a shake they move make a dull thud sound on both sides. It has polyurethane bushings in the control arms and they seem to be in pretty good shape but their is still some play giving me a thud. I hear it when I am on a rough road or changing from gas to brake or vice versa. Hope this helps.

  18. #18
    Member jcws6's Avatar
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    I took the driveshaft back to the transmission specialist and showed him that it was not making any noise. He said he was almost positive that the driveshaft is the problem, and it might just need to be rotated. So, he referred me to a drivetrain specialist.

    I talked to the rear end shop, and they said they would need to charge me $60-70 to balance the driveshaft and inspect it for problems. Worthwhile investment, or should I just start saving up for a new rear axle? Discuss.
    Last edited by jcws6; 05-13-2008 at 08:13 AM.

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    Moderator Cutlass's Avatar
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    Well with a noise this tricky there is only so much you can do before you start trying a few things here and there. So either have the driveshaft serviced or pull the diff cover and look for chipped teeth/excessive wear. And yes those fancy rear diff bolts should be 12 points.
    GOOD LUCK!!

  20. #20
    Member jcws6's Avatar
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    Thanks. Before I get the driveshaft balanced, I'm going to get the gear oil changed next week, to check the rear end. I reinstalled the driveshaft for the second time today, and I was hoping to check pinion bearing preload while I was under there. Unfortunately, I didn't have enough space to move the torque wrench between the torque arm on one side & the exhaust pipe on the other.

    However, I did put the car in neutral and yank on the pinion yoke, to check for excessive movement. I couldn't get it to budge more than 1mm or so in any direction. I've pretty much resigned myself to the fact that I have either a ring/pinion or a differential problem. I saw what looked like two alignment marks on the pinion yoke that I didn't put there, so I'm almost convinced the previous owner screwed with the gears.

    If the gear oil change is inconclusive, I'll still get the drivehaft balanced, just for the hell of it. But if it turns out to be anything related to the rear axle, I'll be saving up for a 12-bolt or a 9" or a Dana 60.

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