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Discussion Starter #1
1966 with 302ci, T5 installed about 10 years ago by previous owner, 3.55 rear.

I was at the speedo calculator website (Mustang Speedometer Gear Calculator - because my speedo reads about 5mph faster than actual.

It asks what type T5 I have -- just finding out that there are several types of Tremec T5 trannies that have different "toothed" speedometers.
How can I find out which t5 I have -- or can I check how many toothed speedo I have without pulling the speedo gear?
6, 7, or 8 teeth?

Here's what the website says:
6 Tooth
  • The black 6 tooth internal drive gear was originally used in the 4 speed tranny, but works great to exactly correct for 4.10s when used with a pink 19 tooth driven gear.
  • 83-89 T5 has a yellow 7 tooth internal drive gear
  • 90-95 T5 has a greenish/yellow 8 tooth internal drive gear
  • FRPP M-7003-Z T5 has a yellow 7 tooth internal drive gear
7 Tooth
Select this if you have a:
  • factory 1983-1989 Mustang T5 or AOD
  • Ford Racing M-7003-Z World Class T5
  • Tremec 3550, TKO, TKO 500, TKO 600
  • Tremec T56 Magnum
1996-1998 Cobra T45

8 Tooth
Select this if you have a:
  • factory 1990-1995 Mustang T5, AOD, AODE
  • 1996-1998 GT T45, AODE, 4R70W
  • 1994-1998 V6 T5, AODE, 4R70W

923 Posts
Just see how many teeth are on your current driven gear and get the gear with the next higher count. That will slow down the cable, resulting in a slower speed reading.
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