Clunking Noise from the rear

[brahmabull]

Hey fellas, this question is for the ones that might know my problem and/or have had similar problems, to see if you guys can diagnose this.

2015 Z/28, I have just passed 1500 miles of a mild break in, and went for a spirited drive in the canyons yesterday. My runs consisted of mostly staying in third gear on a very curvy road, and the Z/28 handled real well(I was following my buddy's 2014 Cayman). Never once lost me, and he was surprised I kept up with him. My problem started when we were done, and was driving around the city. Whenever I accelerate from a complete stop upon taking off from first gear, I would hear a couple of clunks until i reached a much higher speed and or until I switch to second gear. The sound is pretty loud, and I could hear and feel it coming from the rear of the car. I had a passenger in the rear, and she stated she could hear and feel it under the seat. My question is, do you guys think this is the Transmission, Differential or the rear axle. I do remember stopping off at a turnpoint, and had to reverse on a downhill. After reversing, and switching back to first gear and accelerating on an uphill, the "HILL ASSIST" came up on the DIC, and I told myself that's weird. Ever sine then, the clunking sound would happen. I am scheduled to bring it to the dealership first thing in the morning to see what is the culprit, but I just cant fathom to think that after a mild break in that this car that is made to handle some track abuse, would not be able to handle a spirited drive in the canyons. Anybody had this similar thing occur to them with this car or any other car?

[jsd]

Hill assist in the z28???

I think the z28 is a track car


For what we need the hill assist in a track car

[blessedhellride]

Sounds like diff. Some zl1 have had this issue.

[2SSRS@Gen5diy]

Originally Posted by brahmabull

Hey fellas, this question is for the ones that might know my problem and/or have had similar problems, to see if you guys can diagnose this.

2015 Z/28, I have just passed 1500 miles of a mild break in, and went for a spirited drive in the canyons yesterday. My runs consisted of mostly staying in third gear on a very curvy road, and the Z/28 handled real well(I was following my buddy's 2014 Cayman). Never once lost me, and he was surprised I kept up with him. My problem started when we were done, and was driving around the city. Whenever I accelerate from a complete stop upon taking off from first gear, I would hear a couple of clunks until i reached a much higher speed and or until I switch to second gear. The sound is pretty loud, and I could hear and feel it coming from the rear of the car. I had a passenger in the rear, and she stated she could hear and feel it under the seat. My question is, do you guys think this is the Transmission, Differential or the rear axle. I do remember stopping off at a turnpoint, and had to reverse on a downhill. After reversing, and switching back to first gear and accelerating on an uphill, the "HILL ASSIST" came up on the DIC, and I told myself that's weird. Ever sine then, the clunking sound would happen. I am scheduled to bring it to the dealership first thing in the morning to see what is the culprit, but I just cant fathom to think that after a mild break in that this car that is made to handle some track abuse, would not be able to handle a spirited drive in the canyons. Anybody had this similar thing occur to them with this car or any other car?

Originally Posted by jsd

Hill assist in the z28???

I think the z28 is a track car


For what we need the hill assist in a track car

The Z/28 does have hill assist, it came up on me ones till i disconnected it.

Originally Posted by blessedhellride

Sounds like diff. Some zl1 have had this issue.

+1

Do the oil change in the diff and see if that fixes it and dont forget you have a different locker then any other Camaro.

[vdshenoy]

Z/28s do have a different differential that other Camaros. It has a helical gearset and gets rid of the clutch packs that most LSDs have. It is a different torque-sensing LSD design that only the Z/28 gets, and they are more efficient at putting power down. However, they do tend to be noisy at low speeds and around parking lots and tight radius turns (especially since we have no sound deadening).

Are you sure this isn't what you are hearing?

[Front Runner]

Originally Posted by vdshenoy

Z/28s do have a different differential that other Camaros. It has a helical gearset and gets rid of the clutch packs that most LSDs have. It is a different torque-sensing LSD design that only the Z/28 gets, and they are more efficient at putting power down. However, they do tend to be noisy at low speeds and around parking lots and tight radius turns (especially since we have no sound deadening).

Are you sure this isn't what you are hearing?

Interesting........

OP, let us know what the dealer says.

[brahmabull]

Originally Posted by vdshenoy

Z/28s do have a different differential that other Camaros. It has a helical gearset and gets rid of the clutch packs that most LSDs have. It is a different torque-sensing LSD design that only the Z/28 gets, and they are more efficient at putting power down. However, they do tend to be noisy at low speeds and around parking lots and tight radius turns (especially since we have no sound deadening).

Are you sure this isn't what you are hearing?

No man, this is not what I was hearing, I am all too familiar with what you just explained. Coming from a C6 ZO6, that vehicle had it too...I'm all too familiar with those other noises in that car, especially in low speeds, and especially when making tight turns. You especially hear kind of like a scuffing sound on the tires. So to answer your question, no it's not that sound..The sound it was making was more like a "pulling and or tugging kind of Clunk", like it was hitting something.

Originally Posted by Front Runner

Interesting........

OP, let us know what the dealer says.

Will do, i'm anxiously waiting on the results myself. i'm hoping its nothing crazy.

[didon1972]

Originally Posted by 2SSRS@Gen5diy

The Z/28 does have hill assist, it came up on me ones till i disconnected it.



+1

Do the oil change in the diff and see if that fixes it and dont forget you have a different locker then any other Camaro.

So, how did you disconnect yours?

[blessedhellride]

wondering if it has anything to do with the flow of diff fluid from the cooling lines.....iirc zl1 had some issue like this as well

[brahmabull]

I got a little bit of my questions answer. Dealer mechanic advised me that it was the "rear knuckles". He didn't explain how this could happen. Maybe it was just a bad batch? I don't know. What do you guys think?

[X25]

Originally Posted by brahmabull

No man, this is not what I was hearing, I am all too familiar with what you just explained. Coming from a C6 ZO6, that vehicle had it too...I'm all too familiar with those other noises in that car, especially in low speeds, and especially when making tight turns. You especially hear kind of like a scuffing sound on the tires. So to answer your question, no it's not that sound..The sound it was making was more like a "pulling and or tugging kind of Clunk", like it was hitting something.



Will do, i'm anxiously waiting on the results myself. i'm hoping its nothing crazy.

I never heard that C6 Z06 had torsen diff? Actually I am almost sure it has clutch packs like other Camaros except Z/28 since friction modifiers quiet down diffs of all C6s.

Most people think Corvettes get better parts than Camaros. There's no such discrimination at GM; it's all about the particular car's R&D budget and price target.

[brahmabull]

Originally Posted by X25

I never heard that C6 Z06 had torsen diff? Actually I am almost sure it has clutch packs like other Camaros except Z/28 since friction modifiers quiet down diffs of all C6s.

Most people think Corvettes get better parts than Camaros. There's no such discrimination at GM; it's all about the particular car's R&D budget and price target.

Never said that a C6 ZO6 had the "Torsen Diff", what I meant and was refferring to was the scuffing noise from the tires when driving slow and or turning on the Zo6 and the Z/28. Both vehicles from my experience on driving them make that noise.

[brahmabull]

Since I had figured out what was the culprit of whats aching my Z/28. I will ask the mechanic to take a pic of the "Defective/failed" part which is a "rear knuckle". up to this point, I still don't know what exactly how they look like, but once I do, I will be looking for vendors who can make a stronger upgrade which can hold better tolerances. I know this part isn't a "service bulletin" yet, and this is the first one that they have heard of it happening on a Z/28, so I might as well make pre-cautions now and start looking to modify to make that sumbitch stronger so it does not happen again. So does anyone know how this part looks like, and willing to suggest a company able to modify and make an upgrade?

[Zslash28]

Have them explain specifically how the knuckle was clunking. The knuckle has pressed in bushings and a bolted on bearing from what I can see. Nothing about the knuckle in my mind could cause it to clunk unless the other parts were bad.