O/T: Any Transmission Experts? Need you Help!!

muscle96ss · Oct 14, 2007

O/T: Any Transmission Experts? Need your Help!!

I have a 2002 Camaro SS 35th LE Vert w/M6(T-56); no performance mods other than exhaust(CME mated w/GMMG with SLP Y-pipe and hollowed out cats). At around 75,000 miles I started getting 2 different problems. The first problem was that in 2nd gear with hard acceleration the shifter would actually move. It turned out to be the tranny mount and that was replaced. The second problem was that I was getting a real loud grinding noise(sounded to me like metal scraping on concrete) whenever the clutch pedal was pressed in and I was either coasting or slowing down(would not happen when accelerating). The only time it would happen is when the clutch pedal was pressed in and the second you let it out the noise would stop. It would happen in all gears and even sometimes in neutral(In other words say I was in second gear and slowing down to a stop. I would press the clutch pedal in and the grinding noise would start and then when I take it out of gear and put it in neutral without releasing the clutch pedal yet, it would still be grinding. However, the frequency of when it would happen in neutral was around 25%). Other than the actual noise there were no functional problems. In other words I had no problems getting into the gear and the actual operational part of the clutch and tranny were 100% normal. The only symptom was the grinding noise(which I could feel vibrate through the clutch pedal and the shifter). To describe it best, it felt like the shifter was scraping something directly underneath the car.

Anyways, I took it to the shop that works on my car; they specialize and F-bodys and Vettes and seem to know their shit. It turned out that I needed a new clutch and slave cylinder as well. Being that I had gotten 75K miles out of the stock clutch and the fact that I don't have a lot of mods, I opted to stick with a new OEM replacement clutch and not a performance clutch. Got the car back and everything is smooth as silk with no grinding noise.

Fast forward 3 months and 5K miles later(yes, I put a lot of miles on my car lately) and the noise has returned and the symptoms are identical. The only difference is that it is only about 50% as loud now(but still can easily be heard by those outside the car). I brought it back to the shop last night and today they took it apart and could find absolutely nothing wrong with the clutch. Apparently they even tried setting things differently to see if it would make a difference and could not find anything wrong nor get the noise to go away. They are positive that it is coming from the transmission. However, their T-56 specialist(who is also the owner of the shop) was not there today so I will not be able to get an opinion from him on how to proceed until Monday.

My question is this: What would be your opinion as to what is going on and why would the noise have gone away when the clutch was replaced the first time if it was not being caused by the clutch? Any feedback would be greatly appreciated.

warhorse · Oct 14, 2007

sounds like a throwout bearing only when the clutch is pressed in right? However if it was a bad throwout bearing (which a good shop will replace with every new clutch) your shop should be able to easily identify it...

Rambo · Oct 14, 2007

Yea, it's probably what Warhorse said.

muscle96ss · Oct 14, 2007

warhorse said:
sounds like a throwout bearing only when the clutch is pressed in right? However if it was a bad throwout bearing (which a good shop will replace with every new clutch) your shop should be able to easily identify it...

Yep, only happens when the clutch pedal is pressed to the floor and goes away when released. When they took the clutch apart today they checked the throwout bearing, pilot bearing, etc... and there was absolutely nothing wrong with anything clutch related at all. They said that when you press the clutch pedal it increases the load on the tranny and that is why it is only happening when the clutch pedal is pressed.

warhorse · Oct 15, 2007

uhh The clutch links the motor and transmission together via a friction disc and the fly wheel when you press the clutch in it disengages the transmission from the engine. The transmission is definitly not under more stress with the clutch pushed in that doesn't make sense to me at all, be wary if they tell you that now you need expensive transmission work....

oldfella · Oct 15, 2007

Nine times out of ten it will be the throwout bearing. It is under the greatest load while cluch pedal is depressed. This sounds like your trouble. In HP cars it is a constant source of trouble. See if some one makes a heavy duty one or get one that comes out of a GM truck! A good mechanic will know this!

muscle96ss · Oct 15, 2007

warhorse said:
uhh The clutch links the motor and transmission together via a friction disc and the fly wheel when you press the clutch in it disengages the transmission from the engine. The transmission is definitly not under more stress with the clutch pushed in that doesn't make sense to me at all, be wary if they tell you that now you need expensive transmission work....

Let me try to elaborate on what I was trying to say because I probably am not using the proper terminology. When the clutch is engaged the input shaft is spinning but is held in place in a closed system controlled by the engine. When the clutch disengages, the input shaft is no longer attatched to the engine and as it winds down it is no longer under control of the engine as long as the clutch is disengaged(so in a sense it is now an open system; again I am not sure if my terminology is corect). It is during this winding down period that moving the shifter is causing the noise. Since they disassembled the clutch yesterday and found everything to supposedly be working properly and not defective, they are assuming that it is something internal in the tranny that is transpiring during the winding down phase that is causing the noise.

muscle96ss · Oct 15, 2007

oldfella said:
Nine times out of ten it will be the throwout bearing. It is under the greatest load while cluch pedal is depressed. This sounds like your trouble. In HP cars it is a constant source of trouble. See if some one makes a heavy duty one or get one that comes out of a GM truck! A good mechanic will know this!

Based on the symptoms, that was what they initially thought that they were gonna find(or possibly the pilot bearing). They checked the throwout bearing yesterday and said it was fine.

oldfella · Oct 15, 2007

Inside the tranny there are a series of bushes. These allow the gears to be moved around and sloted into position when required. it may be one of these that is worn or as they say dried out. What you need is an M22 rock crusher. Bullet proof and the best HP tranny going.

Jarconis · Oct 15, 2007

actually, if you have the $$$, a company called Jericho Transmissions, they make clutchless road racing 5 sp's ( no overdrive, so its really like have a 6 speed) and they are good for up to 1500 hp.

try to break that.

Mackster · Oct 15, 2007

I was thinking throw out bearing when I initially read this, but 5k miles since changing it is not that long. Sometimes these parts can still fail when new, but sounds like the shop has already looked into that.

Yeah, I think it sounds like the tranny to me. Could be a bearing or synchro. Are you wanting to do any mods to the car? Boost up the HP a bit? Or just keep it as is for a while?

Just read its a stock car... Just replace it with another stock unit. No need to spend a lot of money on it unless your planning to do more to it. I replaced the transmission in my Jeep not too long ago and just got one from a salvage yard with 15k miles on it. Very cheap and reliable solution.