92 recalibrate to 3.73 rear end

[Ronald N.]

I have recently purchased a modified 1992 Vette. The rear end has been changed to a 3.73. The problem is the speedometer reads VERY WRONG. Does anyone have a suggestion as the best way to fix this? The tire size is 17" rim with 25.5' diameter tire. I have contacted the "Yellow Box Speedo Recalibrator" but they don't think their's will work on a '92 because of it's "unique" 2-wire sensor. It can be used on a STANDARD 2-wire inductive coil type speed sensor or a 3-wire hail-effect type sensor. The local Chevy dealers are guessing and really don't know if changing the driven gear would even work. One helpful parts manager told me that this car started as a 2.59 ratio. Which his information shows has a 17 tooth drive gear and a 36 toothed driven gear. BUT, because he said it is an electric speedometer changing these would not help. Others have said it might. THANKS for any help you can offer.

[William C.]

Re: 92 recalibrate to 3.73 rear end

The good news is that the basic laws of mechanics that work on an old-fashoned speedo drive also work on the electronic units. The 2.59 gearset used a 36 tooth driven gear part number 25513043, at least per my '89 parts book. you would need about 1.44 times that number of teeth to get the correct drive, and that would give you a 52 tooth gear which is not manufactured. If the electronic sensor screws onto a traditional speedo-style outlet at the trans, I'd look at a reducer, available thru truck parts suppliers or speedo shops the get the system in better sync. A .7 reducer should get you in the ballpark I believe.