Possible Transmission Issue, Or Something Else?

[hottrodcrazy]

I have a '91 ZR1 that I bought almost 2 years ago. It has 6,000 miles on it. I drove it 3 miles and parked it. There were no problems or unusual sounds at that point.

I drove it last week and it's making a noise that sounds like it's in the transmission. The sound is always there when the car is moving in gear, any gear if gear, and when in neutral no noise. I took it to the local dealership, which has a designated Corvette mechanic that it known to be one of the top in our area and he diagnosed it as a transmission issue, but said they did not have the parts and would be unable to locate them, therefore he could not work on it and I had it towed home.

But, he did not take it apart or give a specific diagnosis, so really, I don't even know for 100% it is a transmission issue.

There is oil in the transmission and again it's only got 6,000 miles so I'm wondering if anyone has any ideas or has maybe had transmission issues with their '91 that they could tell me a little about so I could see if potentially that's my issue.

Thanks!

[Kevin]

could you describe the noise for us? or maybe a cell phone vid or gopro? The black tag transmissions have a distinct gear wine that comes from them.

[Roadster]

Welcome to the forum, you will enjoy it here.....:)
Sounds like you have a nice low mileage Z......
What I don't understand is how your mechanic determined that you have a trans problem and would have been ready to order parts if he could get them!!!
Did he tell you what parts he thought were defective and needed to be replaced???
Just buying mine back in April, I probably have the same or similar noise that you have....when you depress the clutch pedal, noise goes away, of course when you let the clutch pedal out and put the vehicle in motion, the noise is present. I thought it sounded like the throw-out bearing, and another member also mentioned that it could be the pilot bearing making this noise (or sound).
Either or, apparently it is no biggie, I have no problems driving with mine with that noise, in fact I just block it out, and don't even notice or pay attention to it anymore.
Why did you have it towed????
Does it not move under its own power???
Is there any problem putting the vehicle in motion and shifting the trans???
You mentioned that you drove it 3 miles 2 years ago and parked it, don't you think that some "things" might have dried up a little over that time, and need more movement to get everything properly lubricated once again???
If someone drove you 3 miles and parked you for 2 years without any movement, what do you think would happen to you???
I think you should drive your Z, unless it won't move under its own power and is making such a noise that in fact it would indicate that something is broken...JMO

[hottrodcrazy]

could you describe the noise for us? or maybe a cell phone vid or gopro? The black tag transmissions have a distinct gear wine that comes from them.

I don't have a video handy, but I'll try to get one ASAP as maybe that will help, but for now I'll do my best to describe it. I know it's not a normal noise. For one I didn't hear it on the first drive and second, it's just one of those things that does not in anyway sound normal. As soon as I heard it I knew there was an issue, but to be honest I thought maybe it was a wheel bearing. If nothing else based on where the noise seems to be coming from I didn't think it was transmission.

The best I can really say is that as long as it's in gear it's a continuous whining sort of noise, but definitely not a grinding sound. I hope that helps, but like I said I'll try to get a video posted so you can actually hear it.

[Kevin]

sounds like it may just be the gear whine from the trans

[hottrodcrazy]

Welcome to the forum, you will enjoy it here.....:)
Sounds like you have a nice low mileage Z......
What I don't understand is how your mechanic determined that you have a trans problem and would have been ready to order parts if he could get them!!!
Did he tell you what parts he thought were defective and needed to be replaced???
Just buying mine back in April, I probably have the same or similar noise that you have....when you depress the clutch pedal, noise goes away, of course when you let the clutch pedal out and put the vehicle in motion, the noise is present. I thought it sounded like the throw-out bearing, and another member also mentioned that it could be the pilot bearing making this noise (or sound).
Either or, apparently it is no biggie, I have no problems driving with mine with that noise, in fact I just block it out, and don't even notice or pay attention to it anymore.
Why did you have it towed????
Does it not move under its own power???
Is there any problem putting the vehicle in motion and shifting the trans???
You mentioned that you drove it 3 miles 2 years ago and parked it, don't you think that some "things" might have dried up a little over that time, and need more movement to get everything properly lubricated once again???
If someone drove you 3 miles and parked you for 2 years without any movement, what do you think would happen to you???
I think you should drive your Z, unless it won't move under its own power and is making such a noise that in fact it would indicate that something is broken...JMO


What you said about the mechanic is exactly why I'm on hear asking and not even sure it's a transmission issue. He gave me no specific diagnosis or parts needed, and as I said he didn't take the trans apart, so basically it was just a guess on his part.

I do understand that without driving it for nearly 2 years things will dry up and need to be relubricated and frankly can go bad from not being driven. I drove it far enough that if that was all that was needed the noise would have atleast let up some, thus I drove it in to have it looked at.

I chose to have it towed because upon first hearing this supposed diagnosis from a very reputable corvette mechanic my first instinct was that I didn't want to add miles and possibly damage the car. But now that I've gotten it home and had some time to think it over, I'm more and more unsure the transmission is the issue.

I'm hoping it's a much less expensive issue and an easier fix than a transmission issue, and maybe it is a transmission issue where the car was serviced and the fluid was drained and replaced with the incorrect fluid. I haven't had a chance to investigate myself and was hoping to find someone with some insight or who has maybe had the same experience. I'll definitely look into the issues you mentioned, so thanks for mentioning them.

[Roadster]

What you said about the mechanic is exactly why I'm on hear asking and not even sure it's a transmission issue. He gave me no specific diagnosis or parts needed, and as I said he didn't take the trans apart, so basically it was just a guess on his part.

I do understand that without driving it for nearly 2 years things will dry up and need to be relubricated and frankly can go bad from not being driven. I drove it far enough that if that was all that was needed the noise would have atleast let up some, thus I drove it in to have it looked at.

I chose to have it towed because upon first hearing this supposed diagnosis from a very reputable corvette mechanic my first instinct was that I didn't want to add miles and possibly damage the car. But now that I've gotten it home and had some time to think it over, I'm more and more unsure the transmission is the issue.

I'm hoping it's a much less expensive issue and an easier fix than a transmission issue, and maybe it is a transmission issue where the car was serviced and the fluid was drained and replaced with the incorrect fluid. I haven't had a chance to investigate myself and was hoping to find someone with some insight or who has maybe had the same experience. I'll definitely look into the issues you mentioned, so thanks for mentioning them.

Your welcome, no problem....:)
As you have mentioned, it may not be a trans issue after all. Since the vehicle only has 6000 miles, it seems that it highly unlikely that their is an issue with the trans or anything else for that matter. Again, if the Z drives good, and the noise mentioned is a low level noise, then IMO I don't think you have a major problem. On the other hand, if the noise is loud to the point that you can't focus on driving the vehicle, then I would have it checked out for a safety inspection, suspension, wheel bearings, ball joints, etc., to determine what and where the noise is originating.....
You mentioned about the trans fluid being changed, was it changed, or do you think it was a possibility it was changed???

[hottrodcrazy]

A few other things I just thought to add, I said it doesn't sound like grinding, but I should amend that. It has a bit of a grinding sound, but NOT like gears grinding, definitely not like gears grinding.

I have a mechanical friend that listened and said it sounds like it may be in the main shaft of the transmission. And in regards to the mention of the pilot bearing or the throw out bearing - I honestly don't know what an issue with the pilot bearing would sound like and I don't believe it's the throw out bearing based on where the sound is coming from. The sound seems to be coming from the middle of the car. And it's a loud enough sound that when driving it others can hear it from maybe 100 feet away, which is another reason I had it towed and won't drive it as is because something is obviously going on with it.

Part of my asking was to see if this is a somewhat common ZR1 issue. Also, is the transmission the same that would be found in any other manual c4 corvette? That's something I honestly don't know, but if so then finding parts should definitely not be an issue.

Thanks again for help and thoughts! And I don't guess anyone by any chance knows a reputable corvette mechanic in the Charlotte area do they?

[hottrodcrazy]

Your welcome, no problem....:)
As you have mentioned, it may not be a trans issue after all. Since the vehicle only has 6000 miles, it seems that it highly unlikely that their is an issue with the trans or anything else for that matter. Again, if the Z drives good, and the noise mentioned is a low level noise, then IMO I don't think you have a major problem. On the other hand, if the noise is loud to the point that you can't focus on driving the vehicle, then I would have it checked out for a safety inspection, suspension, wheel bearings, ball joints, etc., to determine what and where the noise is originating.....
You mentioned about the trans fluid being changed, was it changed, or do you think it was a possibility it was changed???


The dealership did a 28 point inspection and found no issues, they did not change the trans fluid and if they did they did not tell me. I was thinking in an earlier service it was probably changed and for all I know the incorrect fluid was used, but I've not had time to check into it to know, that's just a guess of a possible issue.

And it's definitely not a low level noise, which is part of why I had it towed home. But I agree, it definitely may not even be a trans issue, thus the title for my thread. That certainly wasn't my first guess...

[Roadster]

Ok, just based on your previous post, and thinking out loud.......
check your u-joints on the drive shaft and the half shafts, it may be a possibility that you have a bad u-joint...again just thinking out loud.....
if people can hear this noise 100 feet away and it is above the engine noise, then yes, there is something goin on.....

[Roadster]

I mean then again, it could be something loose that when you put the vehicle in motion, it is rubbing or vibrating against something else during that time and producing the noise you are hearing...
some questions???
1-is the vehicle drivable?
2-can you shift the trans with no problem?
3-are you experiencing any clutch slippage?
4-with the vehicle stopped and in gear with the clutch pedal depressed of course, is the noise present?
5-with the vehicle stopped and not in gear, any noise? if you depress the clutch not in gear, any noise?
6-with the vehicle stopped and either in gear or not in gear and reving the engine, any noise?
7-when in motion and in gear, noise is present, correct? if you depress the clutch pedal in gear when in motion, is noise still present?

[Roadster]

Part of my asking was to see if this is a somewhat common ZR1 issue. Also, is the transmission the same that would be found in any other manual c4 corvette? That's something I honestly don't know, but if so then finding parts should definitely not be an issue.


As far as the trans goes, I don't remember if the other C4's from that time used the same ZF 6speed, and since I'm old and sometimes confused, and lazy at the moment, I can't give you a correct answer.....

[Kevin]

89-96 are zf cars. 93 they went to the blue tags

[hottrodcrazy]

I mean then again, it could be something loose that when you put the vehicle in motion, it is rubbing or vibrating against something else during that time and producing the noise you are hearing...
some questions???
1-is the vehicle drivable?
2-can you shift the trans with no problem?
3-are you experiencing any clutch slippage?
4-with the vehicle stopped and in gear with the clutch pedal depressed of course, is the noise present?
5-with the vehicle stopped and not in gear, any noise? if you depress the clutch not in gear, any noise?
6-with the vehicle stopped and either in gear or not in gear and reving the engine, any noise?
7-when in motion and in gear, noise is present, correct? if you depress the clutch pedal in gear when in motion, is noise still present?


The more I think on it the more I'm leaning towards the possibility that when it was prepped for sale - it's a two owner car, I'm the second owner and the original owner passed away from my understanding and for all I know when his kids prepped it for sale they could have the grease changed and replaced with the wrong thing. It's just a guess and possibly wishful thinking.

But to answer your questions...
1. it is driveable
2. shifting is no problem
3. there is no clutch slippage
And, as long as the car is in gear the noise is present. Knock it out of gear and put it in neutral and the noise goes away.

[Roadster]

The more I think on it the more I'm leaning towards the possibility that when it was prepped for sale - it's a two owner car, I'm the second owner and the original owner passed away from my understanding and for all I know when his kids prepped it for sale they could have the grease changed and replaced with the wrong thing. It's just a guess and possibly wishful thinking.

But to answer your questions...
1. it is driveable
2. shifting is no problem
3. there is no clutch slippage
And, as long as the car is in gear the noise is present. Knock it out of gear and put it in neutral and the noise goes away.

Based on what you are saying, I don't think it has anything to do with the car being prepped, grease being replaced with wrong thing, I don't think so.
Either it is the throw-out or pilot bearing making the noise since when you put in it neutral, the noise goes away. Unless it is something really weird to when being in gear the torque of the motor is creating this sound and of course when your out of gear with the vehicle in neutral, the torque of the motor is non-exsistent, thus not creating any said noise.
IMO, it is one of those bearings making the noise. As suggested earlier by Kevin, get a sound bite so we can listen.....