Transmission Issues
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4th Gear
Joined: Aug 2016
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Transmission Issues
I have a 1986 corvette Z51 in running condition. It has a Doug Nash 4 + 3 manual with overdrive. The car had been sitting for about five years before I bought a new battery and started it up. It runs pretty smoothly, my only issue is the transmission. I'm not sure how serious it is, but there is a loud humming in every gear whether or not I'm in overdrive. Also, overdrive doesn't automatically shut itself off in 1st gear even though it's supposed to. I have no clue whether these two issues are related. Any help would be appreciated.
P.S. Praying it just needs the transmission fluid filled up.
P.S. Praying it just needs the transmission fluid filled up.
Melting Slicks
Joined: Jan 2014
Posts: 2,181
Likes: 380
From: Lunenburg MA
I have a 1986 corvette Z51 in running condition. It has a Doug Nash 4 + 3 manual with overdrive. The car had been sitting for about five years before I bought a new battery and started it up. It runs pretty smoothly, my only issue is the transmission. I'm not sure how serious it is, but there is a loud humming in every gear whether or not I'm in overdrive. Also, overdrive doesn't automatically shut itself off in 1st gear even though it's supposed to. I have no clue whether these two issues are related. Any help would be appreciated.
P.S. Praying it just needs the transmission fluid filled up.
P.S. Praying it just needs the transmission fluid filled up.
Probably not a lack of fluid problem. There's usually a reason someone lets a car sit for 5 years. Hope you got the old gas out of it before you tried to start it.
Melting Slicks
Joined: Mar 2016
Posts: 2,778
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From: Langley BC
I'm not sure if this is a fluid related Issue, but if the car has been sitting for 5+ years, You should drain the old fluid out of the trans and refill to the correct level before you drive it anywhere. In fact basically all the fluids in the car should be changed in the car before you drive it.
Try changing the fluid and see what happens it can't hurt!
let us know if the noise remains after the fluid change.
Try changing the fluid and see what happens it can't hurt!
let us know if the noise remains after the fluid change.
Last edited by DMITTZ; Aug 4, 2016 at 10:46 PM.
Thread Starter
4th Gear
Joined: Aug 2016
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Does it hum with the clutch pedal depressed? Sometimes people bypass the first gear switch, either because it failed or because they want OD in every gear. It's a bad idea though as the OD pump is driven by the rear wheels.
Probably not a lack of fluid problem. There's usually a reason someone lets a car sit for 5 years. Hope you got the old gas out of it before you tried to start it.
Probably not a lack of fluid problem. There's usually a reason someone lets a car sit for 5 years. Hope you got the old gas out of it before you tried to start it.
Melting Slicks
Joined: Mar 2016
Posts: 2,778
Likes: 580
From: Langley BC
Is it making a noise when the car is stopped?
If the car is parked /stopped and the clutch is depressed or trans is in neutral, and it is still humming I don't think your issue is U-joints since they are only in motion when the car is moving.
If the car is parked /stopped and the clutch is depressed or trans is in neutral, and it is still humming I don't think your issue is U-joints since they are only in motion when the car is moving.
Thread Starter
4th Gear
Joined: Aug 2016
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It makes noise whenever the clutch is out, even in neutral.
Melting Slicks
Joined: Mar 2016
Posts: 2,778
Likes: 580
From: Langley BC
If that is the case it sounds like the noise is coming from the transmission itself...
I would park it until you can change the fluids in the trans and overdrive, and then see if the noise remains. I wouldn't risk driving it until you know it has enough fluid, as running dry or low on fluid could be very bad.
I would park it until you can change the fluids in the trans and overdrive, and then see if the noise remains. I wouldn't risk driving it until you know it has enough fluid, as running dry or low on fluid could be very bad.
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Thread Starter
4th Gear
Joined: Aug 2016
Posts: 4
Likes: 0
If that is the case it sounds like the noise is coming from the transmission itself...
I would park it until you can change the fluids in the trans and overdrive, and then see if the noise remains. I wouldn't risk driving it until you know it has enough fluid, as running dry or low on fluid could be very bad.
I would park it until you can change the fluids in the trans and overdrive, and then see if the noise remains. I wouldn't risk driving it until you know it has enough fluid, as running dry or low on fluid could be very bad.
Melting Slicks
Joined: Mar 2016
Posts: 2,778
Likes: 580
From: Langley BC
Changing the fluid is a good first step, as it will rule out the easy fix and you can see if there are any metal particles in the old fluid...
Otherwise the only other thing I can think of is you may have internal transmission problems or it might be a bad pilot bearing, both of which would require the trans to be removed to repair.
Otherwise the only other thing I can think of is you may have internal transmission problems or it might be a bad pilot bearing, both of which would require the trans to be removed to repair.