Rear End Clunk - Driveline

[Rawyzf]

If I am rolling and holding a gear, low RPM, and blip the gas and let of, I can hear and feel a clunk while catching and engaging power and the clunk when letting off.

Sounds like a bowling ball rolling around in the spare wheel well :p

Any idea where to start with this?

I don't think its transmission, I had the fluid level checked and it was good.

It feels like something is loose in the driveline/driveshaft in my opinion. Feels sloppy.

[I12XLR8]

Very strange. I just noticed the same thing a few days ago but mine is more intermittent. It seems to only happen if I brake hard right after an up shift, but not every time.

I assumed it was something loose in the trunk but emptied the trunk last night and was able to make the noise this morning. I am very interested in opinions on this.

I have the GXP rear if that changes anything.


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[Rawyzf]

That is how mine started, didn't do it all the time. It's getting pretty bad now, as to where I need to bring it in. It does cluck more often when downshifting coming to a stop too, upshifts at high rpm are not an issue.

I have the Camaro 3.45 Differential.

[vert]

In older cars it usually was a sign that a u joint was going out, so I would think I would start with the driveshaft. Might check the rubber couplers and give the shaft a turn with your hand to see if it has any play. Driveshaft that is. LOL

[Rawyzf]

In older cars it usually was a sign that a u joint was going out, so I would think I would start with the driveshaft. Might check the rubber couplers and give the shaft a turn with your hand to see if it has any play. Driveshaft that is. LOL

Thanks Vert.

U-Joint, have any pics of what/where that is. I recall trying to spin the driveshaft a few months ago and it had no play. Also, rubber couplers, let me know what you mean by those. I'm a visual person, lol.

[Rawyzf]

Found this thread, so I can visualize.

Are the U joints the ends of the driveshaft, shaped like a U? (:D)

http://forum.grrrr8.net/showthread.php?t=30209&highlight=u-joint

[Rawyzf]

Found this thread too, sounds like the last 3 posts are exactly what is wrong. Now I need to know what thier cure was.

http://forum.grrrr8.net/showthread.php?t=17250&highlight=u-joint

[vert]

Not sure if you saw this from CP, parts diagram
http://forum.grrrr8.net/showthread.php?t=14220

[Rawyzf]

Yup, thanks!

I just printed this out and plan to check bolt tq specs on mine. I am not sure how to tell if the UJoint is bad, but I'll crawl around and take a peek :)

[Rawyzf]

Ok, just crawled under the car. I can turn the driveshaft a tiny bit and it clanks as I go back and forth. Bolts seem tight though.

[Rawyzf]

Video of Driveshaft movement, LMK if you think this is an issue:

http://www.youtube.com/watch?v=b4BqcveV_Ds

[Rawyzf]

While I was under, I also tried twisting the front of the driveshaft by the Tranny. That side didn't seem to make as much noise. There was only a very tiny amount of play up there, compared to the rear it seemed.

[Rawyzf]

One more thing :)

While looking at the Diff I noticed that the Pass side bushing had a little gap, I am wondering if I can tighten that up some?

Driver Side, No gap:

http://i467.photobucket.com/albums/rr35/Rawyzf/PontiacG8GT/Misc/DiffDriverSide.jpg

Pass Side, Gap:

http://i467.photobucket.com/albums/rr35/Rawyzf/PontiacG8GT/Misc/DiffPassSide.jpg

[spartan466]

Subscribed. I noticed the same clunk after I put in my gForce axles and thought it was the new CV joints in the axles, but when I went under there to check, I have the exact same slop in the driveshaft/diff as in your video. So, not sure if it's normal slop or if I'm starting down the slow path of killing my diff. :shutup:

[Rawyzf]

Charlie told me that some play is ok, so I am not sure if that is what is causing my clunking.

I'm hoping others who have had this issue will post what the found for a cure.

[Eidolon]

There's always a little bit of play in the shaft through the gears in the diff. But various mods either increase it or make it more apparent.

New bushings in the rear end will make the clunk more noticeable because they transmit it to the chassis. Rawzyf, it looks like you're running the BMR Street bushings, so that'll give you some noticeable transmission of additional diff noise. You may also notice a slight whine on the highway even though your diff fluid is topped up.

I also wouldn't worry about that gap between the bushing "flange" and diff unless the bolt through the diff is loose. The gap between the bushing flange and the diff body will be there because the bushings are internally mated to one another and that half couldn't be pressed in any further.

If you're running GForce axles, the CV joints do have ever so slightly more play. You can evince this by putting the rear up, leaving the car in gear (or in Park to lock the shaft) with the parking brake off, and rotating a wheel by hand. The shaft shouldn't be allowed to move by the transmission, but that lone wheel will still wiggle back and forth. In my car, this does result in a very noticeable low speed clunk when switching from forward to reverse and back. It's been there and more noticeable since the day I installed both the differential bushings and the GForce shafts, but 12,000 miles later, it's still good to go.

[jscruick]

check diff. fluid; a drain and refill with carbon diff. fluid cured my noise problem!

[Eidolon]

check diff. fluid; a drain and refill with carbon diff. fluid cured my noise problem!
That is something to try, and it's not too spendy. GM dealers stock the stuff, and it's about $35 per liter, I want to say. You'll need two. I want to say the diff takes... 1.4 quarts? If the fluid's never been changed, it can't hurt, either.

[spartan466]

There's always a little bit of play in the shaft through the gears in the diff. But various mods either increase it or make it more apparent.

New bushings in the rear end will make the clunk more noticeable because they transmit it to the chassis. Rawzyf, it looks like you're running the BMR Street bushings, so that'll give you some noticeable transmission of additional diff noise. You may also notice a slight whine on the highway even though your diff fluid is topped up.

I also wouldn't worry about that gap between the bushing "flange" and diff unless the bolt through the diff is loose. The gap between the bushing flange and the diff body will be there because the bushings are internally mated to one another and that half couldn't be pressed in any further.

If you're running GForce axles, the CV joints do have ever so slightly more play. You can evince this by putting the rear up, leaving the car in gear (or in Park to lock the shaft) with the parking brake off, and rotating a wheel by hand. The shaft shouldn't be allowed to move by the transmission, but that lone wheel will still wiggle back and forth. In my car, this does result in a very noticeable low speed clunk when switching from forward to reverse and back. It's been there and more noticeable since the day I installed both the differential bushings and the GForce shafts, but 12,000 miles later, it's still good to go.

Thanks... I've read that other people notice a little bump with the gForce axles. I'm not panicking about it right now as everything is still pretty solid in the driveline and even on DRs, I haven't noticed any issues. With all the extra power I have since the Maggie, I'm actually VERY cautious about taking up driveline slack before doing a burnout or launch though... especially now that I see what kind of slop there is in the driveline. The last thing I need is for all that torque to get a running start at my drivetrain!

[thebeast]

I have the same sound. Hasn't caused any issues, but is very noticeable

[Rawyzf]

I tried to capture the noise in the car, LMK if you can hear it.

http://www.youtube.com/watch?v=UBOWhh22c2g

[Crazy Paul]

Ok, just crawled under the car. I can turn the driveshaft a tiny bit and it clanks as I go back and forth. Bolts seem tight though.

You could be a little more scientific about it by testing each of the joints individually to see if there's any particular section with excessive slop or backlash.

eg:
Start at the gearbox output flange(A)
Hold flange A stationary and try to rotate the rubber coupling(B)
Clunk Y/N

Next hold the rubber coupling(B)
Try and rotate the front secton of tailshaft(C)
Clunk Y/N

Next hold the front section of tailshaft(C)
Try and rotate the front section of splined shaft before the Universal joint(D)
Clunk Y/N

Next hold the front half of the Universal joint(D)
Try and rotate the rear section of tailshaft(E)
Clunk Y/N

Next hold the rear section of tailshaft(E)
Try and rotate the rear rubber coupling(F)
Clunk Y/N

Next hold the rear rubber coupling(F)
Try and rotate the diff pinion flange(G)
Clunk Y/N


http://i2.photobucket.com/albums/y20/PerthPurplePenguin/car%20parts/Tailshaft/DS1_04800.jpg

http://i2.photobucket.com/albums/y20/PerthPurplePenguin/car%20parts/Tailshaft/VE-Tailshaft1000.jpg

[drumsbh]

Your exhaust sounds good though!

[Rawyzf]

Thanks everyone, I'll continue to research the issue and report back.

What I have going on isn't normal, I know that. It's also not the inherited noise from aftermarket bushing/braces. I've had all these parts on for 6 months. This has been getting bad/worse over the last 3 months.

[09g8gt09]

I have the same issue. I just took my car to the dealer for it. At first they couldn't replicate it so I went back and showed them how. Prior to taking it in I changed out the springs, shocks, rear cradle bushings, differential bushings, front lower control arms, and the strut mount bushings, it still happened. Dealer tried blaming the new suspension on it the last time I talked to them but who knows what they will blame next. Hope to get a call soon.

[Rawyzf]

I have the same issue. I just took my car to the dealer for it. At first they couldn't replicate it so I went back and showed them how. Prior to taking it in I changed out the springs, shocks, rear cradle bushings, differential bushings, front lower control arms, and the strut mount bushings, it still happened. Dealer tried blaming the new suspension on it the last time I talked to them but who knows what they will blame next. Hope to get a call soon.

Great info. Please let me know what they blame or fix next.

Do all of the g8s come with 100k power train warranties?


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[SpeedRacerX]

Do all of the g8s come with 100k power train warranties?

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They should.

Also, I have that noise too but very, very slight and minor compared to that. Comes and goes. Yours is not normal although I'm just stating the obvious.

[Rawyzf]

They should.

Also, I have that noise too but very, very slight and minor compared to that. Comes and goes. Yours is not normal although I'm just stating the obvious.

Thanks Randy, I'm going to head to the dealership probably tomorrow then.

[I12XLR8]

I'm not going to bother bringing mine to the dealer...too many mods for them to blame it on. I sure would like to know what they come up with though.

I'm ALMOST hoping that it's the diff; I still have the 2.92 and I love the 3.70 but the hit on fuel consumption is starting to get on my nerves ;-(

[Rawyzf]

Made an appointment for tomorrow, will keep everyone posted.

[Panzer Leader]

Don't know if the V6 driveshaft was different from the Gt or not. Mind developed the dreaded "clunk". It became even more noticable when the ploy bushings were installed. BTW, I thought that if the U Joints went out, a complete new driveshaft was the only answer. Now I see that CP shows a kit available. Is this correct?

[Crazy Paul]

Don't know if the V6 driveshaft was different from the Gt or not.
There's 4 different driveshafts in G8's
2008 5 speed auto
2009 5 speed auto
6 speed auto
6 speed manual


I thought that if the U Joints went out, a complete new driveshaft was the only answer.
True when dealing with available GM parts.


Now I see that CP shows a kit available. Is this correct?
False.
No U joint kit.... just Front rubber coupling kit, Rear rubber coupling kit, Fasteners kits.

[09g8gt09]

Well my dealer said it has to be the new suspension. Got the car back drove around the block and the clunk happened again. Well maybe until something breaks then.

[GM Customer Service]

Great info. Please let me know what they blame or fix next.

Do all of the g8s come with 100k power train warranties?


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Rawyzf,

I would be happy to see if you are still in your Powertrain Warranty. Please send me your VIN through PM.

Thank you,

Tina
GM Customer Service

[Rawyzf]

Rawyzf,

I would be happy to see if you are still in your Powertrain Warranty. Please send me your VIN through PM.

Thank you,

Tina
GM Customer Service

Tina,

I talked with my dealer, I'm still within the power train warranty. I have until 100031 :)

Ryan


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[Panzer Leader]

For awhile I toyed with the idea of a GForce custom one piece shaft with servicable/replaceable U Joints. There was a lot of discussion about the "thud"/"clunk" especially when shifting from Park to Reverse. At least that was where I really noticed it. GM said that a certain amount of "slack" was OK and should be expected.

[Rawyzf]

For awhile I toyed with the idea of a GForce custom one piece shaft with servicable/replaceable U Joints. There was a lot of discussion about the "thud"/"clunk" especially when shifting from Park to Reverse. At least that was where I really noticed it. GM said that a certain amount of "slack" was OK and should be expected.

If this ends up being work outside of warranty, I'll be going gforce or something similar.

[Panzer Leader]

Of course, I really thought it was because the driveshaft and transmission were built at the Moscow Number Five Tractor and T-34 Tank Factory (LOL)

[GM Customer Service]

Tina,

I talked with my dealer, I'm still within the power train warranty. I have until 100031 :)

Ryan


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Ryan

Ryan,

Thank you for responding back. Happy to hear you had your question answered about the Powertrain Warranty. If you have any questions, comments or concerns please feel free to let me know.

Thank you,

Tina
GM Customer Service

[-Ray-]

Tina, you are working overtime or your on the west coast.

[Rawyzf]

Dealership Update:

Dropped my car off Fri AM and picked it up after lunch.

They confirmed they can heard the clunking, but said it's normal to have that with IRS. The tech (who I always request to work on my car) said it sounds louder than avg but thought it might be from having the Camaro Diff and Tune. I let him know it's not the Tune, as I've been setup like this for about a yr, and this clunk really only started about a month ago. There has always been slop in the driveline, but no clunk. He said his hands are pretty much tied when it comes to warranty work, because of the Camaro diff in there. He said he could look into it further, but chances are it wouldn't be covered by warranty because of the Diff. (unless it was forsure driveshaft related). But he said everything on the Driveshaft looked and felt good.

So, I am kinda stuck I guess. We talked it over for a bit, and I think the next step will go to the tuners shop and get his opinion on the matter. I am 99% sure it's not tune related though, but he can also help determine what the issue could be. If it's not going to be a warranty fix, I'd rather fix it at his shop anyway since I can go with aftermarket parts if something is indeed wrong.

Not sure when I'll have time to get into his shop, but I'll update this thread when I do.

[youngrushhour]

Thanks... I've read that other people notice a little bump with the gForce axles. I'm not panicking about it right now as everything is still pretty solid in the driveline and even on DRs, I haven't noticed any issues. With all the extra power I have since the Maggie, I'm actually VERY cautious about taking up driveline slack before doing a burnout or launch though... especially now that I see what kind of slop there is in the driveline. The last thing I need is for all that torque to get a running start at my drivetrain!

gForce axles and a noticeable clunk. They definitely will cause some noises and vibrations, for sure.

[Rawyzf]

Problem has been fixed!

Issue: Pfadt bushings in the diff went bad. We switched them to BMR Street Bushings and the clunk is gone.

[Executor999]

Problem has been fixed!

Issue: Pfadt bushings in the diff went bad. We switched them to BMR Street Bushings and the clunk is gone.

That's great news! I hate clunks. Finally getting my driveshaft replaced. Betting money the new power damaged one of the couplings or the rubber cushion of the center bearing. I"ll find out next week. Been waiting five months to take action on this.

[Rawyzf]

I am super happy to have this fixed. The clunk worried me and I wanted to know what it was and always hoped it wouldn't break something.

I have spare rubber couplers if you end up needing some.

[Executor999]

I am super happy to have this fixed. The clunk worried me and I wanted to know what it was and always hoped it wouldn't break something.

I have spare rubber couplers if you end up needing some.

Thanks for the offer, but I bought brand new ones from Pace - the Camaro ones which are cheaper but supposedly better. In fact I bought all new bolts for GR8lover's stock driveshaft. If I break this one, the next step is a Dynotech unit for sure. I don't have a clunk going on but a lot of vibration between 45 and 70mph when accelerating hard.

[Rawyzf]

Cool, no prob. I bought these couplers from the Camaro forum, just incase mine were bad.

Keep me posted on how it goes.

[RuLEoF2]

Hi...

Obviously this is a pretty old thread but I figured I'd post anyway since my issue seems to be the same as what the OP was dealing with. My symptoms are nearly identical to what is shown in his video. I've got more trouble-shooting to try but if my situation is due to bad rubber drive-shaft couplers or the differential bushings that ended up being the cause of the OP's clunking sound, how difficult is it to replace those items? Is it a driveway job or is it something that needs to be done on a lift?

Thanks.

[Rawyzf]

Hi...

Obviously this is a pretty old thread but I figured I'd post anyway since my issue seems to be the same as what the OP was dealing with. My symptoms are nearly identical to what is shown in his video. I've got more trouble-shooting to try but if my situation is due to bad rubber drive-shaft couplers or the differential bushings that ended up being the cause of the OP's clunking sound, how difficult is it to replace those items? Is it a driveway job or is it something that needs to be done on a lift?

Thanks.

The Diff bushings are definately not a driveway job, especially if they are the oem bushing which will need to be pressed or drilled out.

Couldn't tell you on the driveshaft couplers, sorry.

[RuLEoF2]

It's been a while and I tried to get this pinned down but no luck. I took it to a transmission shop and the tech there said that he didn't think it transmission related but rather a bad mount somewhere. I took it back to my regular mechanic and they said that all the mounts were fine. So, I kinda gave up for a while.

Over the weekend, I had the rear wheels off and noticed a fair amount of slop in the drive. Take a listen and tell me what you think. Is this normal?

https://www.mediafire.com/download/moxqeyvgw2vqzga

[Rawyzf]

Just watched the video, being that you can move the wheel that much and get the cluck....would wheel bearings be the possible culprit?

It's been a while, but I want to say I replaced mine under some kind of TSB or warranty. (I could be wrong though too, like I said, its been a while).

[RuLEoF2]

Better not be the bearings. I just had them replaced on that wheel to try to fix this wired "whurring" noise that I've had for the last several months. My regular mechanic said that it was "probably" rear bearings and since it sounded like the right side, that's what I went with. Almost $700 later, no dice. The noise is still there. Still don't know what's causing it and oddly enough, it hasn't changed or gotten worse despite rotating the wheels. The brakes seem to be OK too.

[Rawyzf]

See if you have a driveline specialty auto shop around you. Might have better luck with something like that.

[BuildItYourSelf]

I have way more slop then that but I have a manual transmission.
I would do this.
Lift the car up so you can lay under it.
Leave it in Park. And block up one tire.
Have someone move the one wheel back and forth and see if there is more movement from one join to another. Starting with wheel/axle shaft, shaft/inner cv, and on to the other wheel. And then cv's/rear drive shaft, rear/front drive shaft.
I bet its a cv or center bering on the drive shaft.
If it was the rear gear you would have a loud hum when driving.

[BuildItYourSelf]

Also when it's up pull the park break and have someone put it in drive and watch the movement of the diff bushings.

I have a clunk when I let off the throttle bit it's my muffler hitting my diffuser. Only does it when I let off quick of a hard pull.

[G8White1]

Replace your transmission mount with the upgraded GM unit. Thought I had checked it and found it ok. I was wrong. Solved the problem.