1981 speedometer
Thread Starter
3rd Gear
Joined: Jan 2012
Posts: 3
Likes: 0
1981 speedometer
The speedo in my 81 doesn't work at all. Trans is 350 turbo. Took cable off and it has a blue driven gear. Can turn the driven gear by hand and speedo in car moves. Has a red drive gear, but I don't see red on charts for an 81. Can't find ID num for trans, guess its got several coats of paint over the years. Would appreciate any help. Thanks
Race Director
Joined: Oct 2000
Posts: 12,636
Likes: 3,101
From: Shamong, NJ
The 1981 MX3 Turbo 350, was unique to the 81 Corvette. I believe it was a GM "corporate" trans, sourced from GM'S B-O-P (Buick, Olds, Pontiac) division. The 80 Corvette used the Chevrolet Turbo 350, and 82 used the 700-R4 auto.
The Corvette parts book only lists one drive gear for use in the MX3, a green 9 tooth gear. Strangely, both a natural 19 tooth gear, and a blue 20 tooth gear, are listed for use with the 2:87 rear, and either the P225/70R15 or the P255/60R15 tires.
I'd suggest trying to identify if it's the original trans. The 81 Corvette Turbo 350 was identified by the production code, 8JD, which was stamped on a vertical pad, on the passenger side of the trans, by the transmission's oil pan. There should also be a 6 digit code identifying the manufacturing date and plant.
The trans could also have a VIN derivative, that would match your car's VIN number. The VIN derivative, can be found on either a boss on the front right side of the trans, or on the lip of the bellhousing portion on the left side of the trans.
Check your two gears, to see how many teeth each has. You may want try a green 9 tooth drive gear, to see if that fixes the problem. The GM part number for the green 9 tooth gear, is 6261782, though I can't say if it's still available. GM has been discontinuing a lot of the old speedometer gears.
The Corvette parts book only lists one drive gear for use in the MX3, a green 9 tooth gear. Strangely, both a natural 19 tooth gear, and a blue 20 tooth gear, are listed for use with the 2:87 rear, and either the P225/70R15 or the P255/60R15 tires.
I'd suggest trying to identify if it's the original trans. The 81 Corvette Turbo 350 was identified by the production code, 8JD, which was stamped on a vertical pad, on the passenger side of the trans, by the transmission's oil pan. There should also be a 6 digit code identifying the manufacturing date and plant.
The trans could also have a VIN derivative, that would match your car's VIN number. The VIN derivative, can be found on either a boss on the front right side of the trans, or on the lip of the bellhousing portion on the left side of the trans.
Check your two gears, to see how many teeth each has. You may want try a green 9 tooth drive gear, to see if that fixes the problem. The GM part number for the green 9 tooth gear, is 6261782, though I can't say if it's still available. GM has been discontinuing a lot of the old speedometer gears.
Thread Starter
3rd Gear
Joined: Jan 2012
Posts: 3
Likes: 0
1981 speedometer
The 1981 MX3 Turbo 350, was unique to the 81 Corvette. I believe it was a GM "corporate" trans, sourced from GM'S B-O-P (Buick, Olds, Pontiac) division. The 80 Corvette used the Chevrolet Turbo 350, and 82 used the 700-R4 auto.
The Corvette parts book only lists one drive gear for use in the MX3, a green 9 tooth gear. Strangely, both a natural 19 tooth gear, and a blue 20 tooth gear, are listed for use with the 2:87 rear, and either the P225/70R15 or the P255/60R15 tires.
I'd suggest trying to identify if it's the original trans. The 81 Corvette Turbo 350 was identified by the production code, 8JD, which was stamped on a vertical pad, on the passenger side of the trans, by the transmission's oil pan. There should also be a 6 digit code identifying the manufacturing date and plant.
The trans could also have a VIN derivative, that would match your car's VIN number. The VIN derivative, can be found on either a boss on the front right side of the trans, or on the lip of the bellhousing portion on the left side of the trans.
Check your two gears, to see how many teeth each has. You may want try a green 9 tooth drive gear, to see if that fixes the problem. The GM part number for the green 9 tooth gear, is 6261782, though I can't say if it's still available. GM has been discontinuing a lot of the old speedometer gears.
The Corvette parts book only lists one drive gear for use in the MX3, a green 9 tooth gear. Strangely, both a natural 19 tooth gear, and a blue 20 tooth gear, are listed for use with the 2:87 rear, and either the P225/70R15 or the P255/60R15 tires.
I'd suggest trying to identify if it's the original trans. The 81 Corvette Turbo 350 was identified by the production code, 8JD, which was stamped on a vertical pad, on the passenger side of the trans, by the transmission's oil pan. There should also be a 6 digit code identifying the manufacturing date and plant.
The trans could also have a VIN derivative, that would match your car's VIN number. The VIN derivative, can be found on either a boss on the front right side of the trans, or on the lip of the bellhousing portion on the left side of the trans.
Check your two gears, to see how many teeth each has. You may want try a green 9 tooth drive gear, to see if that fixes the problem. The GM part number for the green 9 tooth gear, is 6261782, though I can't say if it's still available. GM has been discontinuing a lot of the old speedometer gears.
