2004R Speedometer Calibration [Archive] - Chevelle Tech

: 2004R Speedometer Calibration

Jun 4th, 06, 1:07 AM
I just finished putting a 2004R in my 86 Cutlass. I removed it from a 88 Monte Carlo LS. The speedo in the Cutlass is now 20-25 MPH off (reading higher). The cutlass has 3.73 gears in it, not sure what the Monte Carlo had. Is it possible to fix this by changing the cable gear? I can't change the one on the tailshaft since the housing doesn't come off like a TH350 or TH400.

Jun 4th, 06, 1:20 AM
The speedo gear on a 200-4R is on the governor. You can change it but it requires removal of the pan, govenor cover, governor, and partial disassembly of the governor. New gears are about $40 each from GM for the 200-4R drive gear :(
To make such a drastic difference you will likely need to change the drive gear.

What tire size do you have now, and you are sure you have 3.73's right?

Jun 4th, 06, 9:54 AM
Right now it has 255 60 15's on the back, but those are about bald so they will need to be changed soon. Yes I am positive it has 3.73's in it, I put the rear in it.

Jun 4th, 06, 12:04 PM
If you plan on keeping the 255/60-15's, or a tire with the same overall diameter which is approx 27", you need a 10 tooth drive gear which is green for the 200-4R and original to the Monte Carlo SS's, and a 28 tooth driven(yellow).

You could get by with an 11 tooth drive gear (orange) and a 31 tooth driven (white).

I would pull your existing driven gear and look in the hole with a flashlight and see what you have for a drive gear.

GM P/N's are 416765 is the 28 tooth driven about 5 bucks at the dealer.
8639906 on the 10 tooth drive gear, lists for $42.