3.73 w/T5

[stadair]

I just re-read the 3.73 gear posted by "copper", but it does not seem to help me. I just had a 3.73 gear installed and my speedometer is off by +8 mph at highway speed (going 70 mph, speedo indicates 78 mph). THe shop, MRT, installed the red 21 tooth gear in my trans, which is supposed to be the correct gear for the T5. What gives? Is there something to do to the 160 mph speedometer in our cars? My SSP is a '93 w/T5. Orginally it had the 3.08 rear gear. Any suggestions?

[copper]

Toshi,
I had a 21 tooth gear in my 3.73 and it jumped. I read gears that high may get their teeth ground off I replaced it with a 23 tooth I found on eBay and it got it a little closer but that one is starting to jump a little. I have not had it checked for being accurate as of yet, if it holds out. I was told my only other choices are change the trans gear or reduce the rear end or I could just tolorate it. Good luck on yours. Let me know if you come up with a cure for it. George

[stadair]

George,

I read and re-read your thread a few times, trying to get any info for my 3.73/T5 combo. So, you are still trying to figure out something, huh? I did see that I may have to have the driven gear swapped. We shall see.

[FoxChassis]

Borg Warner OEM T-5s had TWO different speedometer "drive" gears; one with seven teeth (7T) or one with eight teeth (8T).

7T = '83-late '89
8T = late '89-'95

A speedometer "driven" gear with 21 teeth (21T) is correct for 3.73:1 only with a 7T drive gear. Your '93 T-5 does not have a 7T drive gear, it has an 8T drive gear. An 8T drive gear with 3.73:1 requires a 24T driven gear, which isn't made. Closest one is 23T. It isn't a Ford gear, it doesn't have the correct pitch to made with the Ford drive gear, and it will eventually wear out, leave plastic pieces in your transmission fluid, and cause the speedometer needle to bounce or stop moving altogether. Not to mention that since 24T is not 23T, the speedometer is not going to be completely accurate.

You have three choices:

Use the 23T driven gear and deal with the eventual consequences. Change the drive gear to 7T or 6T and use the appropriate driven gear. Have a speedometer repair shop install a "gear reducer" in your speedometer cable.

[stadair]

Borg Warner OEM T-5s had TWO different speedometer "drive" gears; one with seven teeth (7T) or one with eight teeth (8T).

7T = '83-late '89
8T = late '89-'95

A speedometer "driven" gear with 21 teeth (21T) is correct for 3.73:1 only with a 7T drive gear. Your '93 T-5 does not have a 7T drive gear, it has an 8T drive gear. An 8T drive gear with 3.73:1 requires a 24T driven gear, which isn't made. Closest one is 23T. It isn't a Ford gear, it doesn't have the correct pitch to made with the Ford drive gear, and it will eventually wear out, leave plastic pieces in your transmission fluid, and cause the speedometer needle to bounce or stop moving altogether. Not to mention that since 24T is not 23T, the speedometer is not going to be completely accurate.

You have three choices:

Use the 23T driven gear and deal with the eventual consequences. Change the drive gear to 7T or 6T and use the appropriate driven gear. Have a speedometer repair shop install a "gear reducer" in your speedometer cable.


This is very helpful. Thank you.