I have an '87 Formula w/T-5 tranny and 9 bolt rear end. I recently upgraded from 3.27 to 3.73's. What steps need to be taken to calibrate my speedo?

 

You need a 7 tooth drive gear and a 21 or 20 tooth driven gear. If you already have the 7 tooth inside the T5, then just remove your VSS, and change the gear to the 20 or 21 tooth and put it back in. If you dont have the 7 tooth, then you need to drop the trans and remove the rear housing to change the gear.

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1991 Camaro Z28
5.7L 5-Speed (originally 305)
317 RWHP, 418 RWTQ
13.23 @ 107.62 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Member: SoCal F-Bodies
-=ICON Motorsports=-

 

If you have 245/50 tires you will need a 21 tooth driven gear for your electric speedo equiped bird. You just got one problem, there all out of stock and GM stoped making them for our cars. Do a search for a product called Dakota digital it might work for you.



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89 T-Top GTA 350 5-speed (soon to be 6-speed)
(Jet hot coated)1 3/4 SLP headers,flowmaster force 2,no cat's,SLP cold air,MSD 6al,march pulleys,ported plenum,air foil,B&M ripper shifter,180 stat,alston SFC,spohn LCA relocation brackets,ES LCA and Panhard bushings,free mods.

0-60 5.2s
Track Time
60' 2.049
E.T. 14.14@96.7MPH (2270 FT)
13.76@99.4MPH corrected

 

Or simply buy an external ratio adapter and plug it into your tranny and the speedo cable. I have a 10-bolt and went from 3.08s to 3.73s so I bought a 0.82:1 adapter. You'll need something like a 0.87 or 0.88:1 adapter. Check with your GM dealer and see what they have.

Hope this helps,

Jason