Speedo Re-calibrated

91Bird305

91Bird305

Club Member
Ever since I did my swap, my speedo has always been off by +15-20mph. Is there anyway to re-calibrate the speedometer to display the correct mph? Car is a 91 Firebird w/ an 87 GN motor swap, 700r4 still and a Dana 60 rear.

Thanks!
 
You must have changed gears or tire size. The only way to change the MPH readout (because it is cable driven) is to change these little plastic gears in the tailshaft of the 700R4 trans. Getting them, installing them, getting the correct ratio gears? Goodluck with that part, im sure the info is out there.
 
There are a few speedo drive vs driven gear calculators that will get you within a tolerance. You need to know your rear axle ratio. Knowing the tire size (if different from stock) will help get even closer.
 
91 is about the year they went electronic.
If you have plastic gears you are in luck. I have every gear & housing in stock & can calibrate what you need with tire height & gear ratio
If its electronic I need to know if the vehicle has a Drac module under the dash (pictured below)
If it has a drac you either need a new one made or one with dip switches installed like the one pictured.... I had several made for this issue with older vehicles.
If it has no drac I think you can recalibrate on the back of the dash.... its been years since I seen one of those.



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