[1982VetteGuy]

Does anyone know what the stock driven gear for the speedometer is in the 1982 Corvette 700r4 transmissions?

I pulled a 42 tooth out of my transmission earlier. The reason why I was asking was because this was a rebuilt transmission I purchased about a year ago. It's not my stock unit, and I do think it came out of a vehicle later than 82.

The speedometer seems accurate.

But I'm installing a TPI set-up on my 82 and am installing a cable driven speed sensor that installs in the transmission.

GM made two speed sensors of this type, using either a 34-39 tooth gear or 40-45 tooth gear.

I bought my harness, ecm, and speed sensor from a company called TPI Parts. I gave him my stock tire height and rear end ratio and he sent me the 34-39 tooth speed sensor based on my calculations. But after I pulled out the 42 tooth gear out earlier, I'm afraid I might have the wrong sensor.

Either way I'm pretty sure i can send this back get the right sensor.

What would happen if I installed a 39 tooth gear instead of a 42 tooth?

Thanks!

 

[WIT911]

bump

 

[TwinTurbo]

what color came out? stock was green 42 if I'm not mistaken.

 

[1982VetteGuy]

what color came out? stock was green 42 if I'm not mistaken.

It was a green 42 tooth driven gear and a 19 tooth drive gear. After creating this thread I remember that I re-used the stock gears from my old tranny.

Which is weird because I used bowtie overdrive's speedo gear calculator and I didn't come anywhere near that.

http://www.700r4.com/speedoCalc/speedocalc.shtml

My car came with the aluminum wheels which according to this website I have 2.87 gears in the rear end.

http://www.corvette-world.com/corvette_1968-82_Rear_Axle%20Ratios_Identification.php

After plugging in the rear end ratio and tire size it said I needed a 17 tooth drive gear and a 36 tooth driven gear for my speedo to be accurate.

I ended up getting those gears from here:

http://www.transmissioncenter.net/speedometer_calibration_______va.htm