1993 Speedo correction

[Ray purple93Z28]

Alright, I hope you guys aren't getting sick of me asking questions yet. I have been out of the car ting for awhile and have forgotten more than I thought. I have a ton of ?'s but will ask as I get to that stageof puttin the car back where it needs to be.
Right now, I am trying to correct my speedo. Does anyone now what gear I need in the A4 since my car now has 3.73 rear gears? (GM part#'s?) THANK YOU so much. I really do appreciate all the help yo guys have given me so far.

[KnightFire]

***Speedo Correction Gears for 93 LT1***

GM p/n 25513052 (44 tooth driven gear) $12.78

GM p/n 8642620 (15 tooth drive gear) $7.56



2.73= 17 tooth[red] and 37 tooth[red]
3.08= 17 tooth[red] and 42 tooth[green]
3.23= 17 tooth[red] and 44 tooth[dark gray]
3.36= 15 tooth[gray] and 40 tooth[black]
3.42= 15 tooth[gray] and 41 tooth[yellow] This is mine
3.55= 15 tooth[gray] and 42 tooth[green]
3.73= 15 tooth[gray] and 44 tooth[Light blue]
4.10= 15 tooth[gray] and 49 tooth[NONE]


KnightFire

[Ray purple93Z28]

Thanks Alot! That was a huge help.

[Ray purple93Z28]

I got the car up and running Sundy...... And the speedo now works great!!! And the tranny is shifting where it should. Thanks alot Bro!!

[blackfire93]

I'm confused?

So if you were to buy those two parts then you wouldn't have to reprogram your PCM for the new gears?

[madwolf]

Yes, that is correct. And also gear correction on 93 ECMs is very limited. Best way to calibrate it is by using the right gears or a speedometer correction module.

[wako29]

what's the deal with this? If you change to rear gears, it will affect the shift points a lot? I just thought it was pretty minor, and your also saying that it will make the speedo not work properly? I thought that only changed with tires sizes.

[Injuneer]

You must be more familiar with the cars that take the speedo sensor off the front wheel..... e.g. front wheel drive cars. On the rear wheel drive setup, the speedo typically is driven off the output shaft of the tranny. Changing the rear axle ratio alters the number of driveshaft/tailshaft rotations per rear wheel rotation, and requires that you correct for the gear ratio change. Up to 1993, they used selectable gears in the speedo drive cable (or driving a VSS). When they went to the 4L60E in 1994, they changed the speed sensor to a reluctor gear on the tranny output shaft, and a magnetic pulse generator type sensor that feeds pulses to the computer. You have to make the corrections in the PCM in that case.

[blackfire93]

installing the gears

I'm going to 3.73 gears and I was wondering if I would be able to install the new speedo gears myself after the mechanic puts the gears in. How hard are they to install and does anybody have any instructions on how to do it?