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Discussion Starter #1
Any one ever had a popping sound, come front what seems like the rear diff or driveshaft? It usually happens on about the second drive of the day once everything is warmed up. And it happens when I'm in traffic. It doesn't jolt or anything. When I'm slowly releasing the clutch from first gear it just makes a popcorn kinda sound, almost like the rear diff is stiff and breaks free if you could imagine how that would sound but like i said it doesn't jolt. Or if i get into 5th and keep it at a certian RPM and let off the gas and jump back on it, its not smooth all the time it kidna kinda pops like the drive shaft is loose or something and rocking back and fourth. Anyone know what this could be?
 

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It's the normal slop in the drivetrain. Most everyone with a GTO has experienced this. It's more prominent in the maunal cars. Basically it will pop or clunk when the driveline goes from unloaded to loaded (at a stop and go to take off) or loaded to unloaded (driving and you let off the gas or push the clutch in).

The rear ends on the GTO's were setup with terrible factory specs. Factory backlash is .007" - .012". It should be down around .005. So basically there's a gap between the ring gear and pinion gear. When your moving the gears are meshed and everything is ok. When the driveline is loaded or unloaded the ring gear will clunk against the pinion gear because of that backlash gap.

Here's what I did to get it to go away 90% of the time:
Rear Subframe bushings
Rear Diff insert bushing
Poly motor mounts (Hinson)
Trans Mount with Revshift Bushing Insert

That stuff took a lot of play out of the driveline and quieted down the clunking. It would still happen here and there but not as bad as stock.

Just recently I got a replacement Rearend under extended warranty (ruined my original at the track) and its waaaayyyy clunkier then my original rearend. So depending on how bad your diff is set up, you may get it to go away with the stuff mentioned above, or you may always have it... Unless you have your rearend rebuilt. I'm so tired of the clunking from this replacement rearend, I just bought a Truetrac Diff and am having my original rear rebuilt.

Hope this info helps!
 

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Discussion Starter #3
Awesome! Thanks for the help! Glad you didn't hit me with some super bad news.... lol Wonder if a new driveshaft and rear diff would make a difference.
 

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No prob! I spent along time chasing that issue lol. Even GM knows about it and didn't warranty it on the factory year cars... said it was normal and not to worry about lol.

And an aftermarket 1 piece ds would probably just accentuate the problem as it's directly connected to the source of the clunk. The factory ds is connected on both ends by rubber and a rubber center carrier bearing.

The only real solution is having the diff rebuilt. That's the stage I'm currently at :smash:

I would say your best bet is motor and tranny mounts. I feel like that made the biggest difference in clunk feel. Then you can add the other bushings. Or just do it all at once and get it over with lol. Car feels much better after that stuff.
 

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Discussion Starter #5
I acutally have new motor mounts sitting right next to me lol and transmisson mount with the blue revshift insert hahahahahah thought that was kinda funny when you mentioned it. And I'm in the process of changing the pinion seal and doing rear diff oil in the next couple weeks
 

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haha nice! Yeah hopefully that stuff helps! I did the diff oil just recently. Pretty easy process but that stuff staaaaaanks lol
 

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Discussion Starter #9
Does it matter it you are turning or going straight when it makes that sound or is one worse than the other?

Sometimes in reverse it REALLY makes a popping sound. and I do hear a pop I want to say at like a perfect cruise in 3rd at like 25mph when i hit bumps and turn. I notice it then, in reverse sometimes, and mostly on the second drive of the day out of first in traffic, or if i play with the gas pedal in like 5th and make sudden gas changes like take my foot off completely in 5th and then just back on it to maintain speed
 

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If this helps...

I found that after a while of owning the car I actually changed my driving style to deal with that clunking. I hate annoying sounds and It was a while before I was able to replace all the bushings. So I used these techniques to help deal with it on the daily.

-I slip the clutch a little more on take off, easing into the rolling motion. This smoothly engages everything and it should be more quiet.
-Rev matching... I always blip the the throttle before releasing the clutch when moving. Especially when downshifting. The closer the engine speed is to drliveline speed during engagment, the less clunk there is... or you can avoid it all together. I made this a huge habit. Will also reduce wear and tear on your clutch.
-If driving at speed and let off, ease back onto the gas gently, then mash it or maintain speed. That will usually avoid the clunk too.

Of course that's not accounting for "spirited driving" or "hot rodding" :)

It's no "solution" but has kept me from pulling my hair out when im in traffic lol After almost 5 years of owning the car I'm finally going to get the diff rebuilt and hopefully never hear a clunk again.
 

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Discussion Starter #11
If this helps...

I found that after a while of owning the car I actually changed my driving style to deal with that clunking. I hate annoying sounds and It was a while before I was able to replace all the bushings. So I used these techniques to help deal with it on the daily.

-I slip the clutch a little more on take off, easing into the rolling motion. This smoothly engages everything and it should be more quiet.
-Rev matching... I always blip the the throttle before releasing the clutch when moving. Especially when downshifting. The closer the engine speed is to drliveline speed during engagment, the less clunk there is... or you can avoid it all together. I made this a huge habit. Will also reduce wear and tear on your clutch.
-If driving at speed and let off, ease back onto the gas gently, then mash it or maintain speed. That will usually avoid the clunk too.

Of course that's not accounting for "spirited driving" or "hot rodding" :)

It's no "solution" but has kept me from pulling my hair out when im in traffic lol After almost 5 years of owning the car I'm finally going to get the diff rebuilt and hopefully never hear a clunk again.
THats what I have been pretty much doing, just trying to baby it, cause i dont have the money to have it rebuilt right now, but I do have all the mounts and stuff like we talked about. I just need to get them in, and I'll probably replace the carrier bearing to just for safe measures.
 

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just trying to baby it
If nothing is actually wrong and your just hearing the normal driveline clunk you don't have to baby it. If by baby it you mean to be smooth so you don't here the pop/clunk then sure but don't be afraid to get on it or slam gears.

The clunk feeling isn't going to hurt anything. I've raced mine like that for the last 4 and a half years. Pretty hard on it on the street as well. During normal traffic driving I tend to ease off it and go for smoothness and gas mileage. But these cars are too much fun not to bangin gears! :)
 

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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.


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

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Discussion Starter #14
Thats the sound! I heard a pop from what seemed like where the driveshaft connects to the transmission, but it only did it once, and the rest came from the normal sound of the rear diff. I wonder if my carrier bearing is bad, i think im gonna chnage it.
 

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Yeah if your carrier bearing is bad or going bad you'll hear knock/pop/clunk type feeling from under the car at lower rpm, usually just 1st gear if it's not too bad. If it's a little worse it's a series of thump, thump, thump, until the driveshaft smooths out with RPM. If you just heard it once it may have just started going bad and have a small tear. (or that sound could have been something else lol)

To check the carrier bearing look at the rubber surrounding it. Look for rips or tears.

This is my torn carrier bearing from a few months ago before the new drive shaft... I was getting a thump, thump, thump in rapid succession for a second or 2 when i took off. Especially if i was getting on it hard from a stop.

 
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