# Rear diff clunk



## Vellas 05 GTO (Jul 16, 2016)

So my 05 gto m6 is starting to clunk upon take off. Did notice also when clutching in when slowing down you hear a noise as well coming from the rear. Has anyone else have this problem before? It's got 77k on the car. I did do a diff flush about 2k miles I did put the synthetic gear oil with the additive like your suppose to. I do have a single piece drive shaft in the car. The ujoints look good no play. Did notice a bit of play by the pinion gear and ring gear ebrake up n I can move the drive shaft quiet a bit. I do hear a cling sound in the rear end when I do this. Any info would help


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## HP11 (Apr 11, 2009)

Isn't that what they're discussing here?


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## svede1212 (Nov 1, 2005)

I don't know where you got the idea you're supposed to put in synthetic. As far as the noise crawl underneath and make sure the center carrier bearing on the drive shaft and the rubber guibo (coupler) on the end are not damaged. Also with both wheels off the ground turn one tire back and forth and see if there is a lot of slop or clunking in the diiff.


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## Vellas 05 GTO (Jul 16, 2016)

I used the 75-140w if I remember correctly can't be 100% sure tho it was a while ago I used what ever my owners manual said to use. I have a single piece drive shaft so no carrier bearing and I bought the one that was a direct bolt on so no guibo's either it goes direct to the tail shaft to pinion gear. The noise wasn't there after drive shaft install this recently started to happen. As for lifting the vehicle up and spinning the tire I'll try that did notice when I spun the drive shaft slightly side to side with the vehicle in the air and ebrake engaged did here a clunk in the diff


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## svede1212 (Nov 1, 2005)

I've heard and seen a few GTO diffs that clunk but you may want to try Torco RGO 85w140 with 2 oz Type "F" friction modifier. You can found it on Amazon. Don't be confused because it says Type "F" is for Fords. Our Australian diffs are a unique animal. The top shops in Oz swear by the Torco dino-lube. It's sounds like that may not be the fix if you have slop but it wouldn't hurt to try. If not I'd start saving up for a rebuild or try to find a good used one.


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## GTO44 (Apr 11, 2016)

That's the normal driveline clunk that about a million GTO owners experience. I've seen at least 100 posts over the last couple years talking about this. GM even knows about it but wouldn't warrany it...

It's due to the terrible tolerances they setup the diff with. When the driveline goes from unloaded to loaded the pinion gear bangs into the ring gear causing the clunking sound. There's techniques you can use to avoid it and bushings you can get to help reduce it that I outlined in the thread that HP11 referenced.

As in the other thread, I Found a video of what actually makes the popping/clunking sound so you visualize what's going on.

At 19sec the driveline goes from loaded to unloaded and you hear the pop/clunk. 






This is what's happening when taking off, between shifts, letting off and getting back into the gas ect.


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## Vellas 05 GTO (Jul 16, 2016)

Thanks guys appreciate it I think Ima upgrade the diff in time. For now I'll just live with it. Glad to know I'm not the only one with this issue


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## sandman1970 (Nov 23, 2016)

What is an "Ebrake?"


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## HP11 (Apr 11, 2009)

sandman1970 said:


> What is an "Ebrake?"


Really?? Emergency brake-parking brake. :surprise:


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