Color of Speedometer Drive gear with a T400 transmission

[Gary C.]

Does anyone know what color speedo driven gear should be for a 75 with a T400, 3.36 and 255/60 tires?

[Joe L.]

Re: Color of Speedometer Drive gear with a T400 transmission

Does anyone know what color speedo driven gear should be for a 75 with a T400, 3.36 and 255/60 tires?

Gary-------


I can tell you what the gear is for stock size, original GR-70-15 tires (741 revs/mile). The 255-60-R15 is slightly different in size (771 revs per mile). However, they are close enough that the original speedometer gears are as close as you are going to get. To get a closer speedometer calibration you would have to use a speedometer adapter.

First of all, a little information on speedometer gear terminology. The speedometer DRIVE gear is the gear that's internal to the transmission and mounted on the transmission shaft. In your case, this is a steel gear originally of GM #8623310 and later GM #8679981. The latter is also discontinued and there may or may not be a new part number.

The speedometer DRIVEN is the gear which runs off the DRIVE gear and can be removed and installed without disassembling the transmission. In your case this would be a nylon (plastic) gear of GM #1359272. This was a 38 tooth gear and of BLUE color. It's GM-discontinued and there may or may not be a new part number.

The DRIVEN gear is used with a sleeve. The gear mounts into the sleeve and the speedometer cable attaches to the sleeve. The sleeve for your application was GM #1362294. It's also discontinued and there may or may not be a new part number.

All of the above parts should be available in the aftermarket and should be able to be cross-referenced from the aforementioned GM part numbers.

[Gary C.]

Re: Color of Speedometer Drive gear with a T400 transmission

Thanks Joe