My speedo is reading lower than I am going and have sort of established that it must be one of 2 things.

1. One of the previous owners has changed the rear end gears. If so, how do I find out what they have been changed to? If it is the rear end gears that have been altered where can I get new speedo gears from?

2. The speedo head is buggered. How do I establish if this is actually the case? Also, can the speedo head be replaced and if so how much is it and where from?

Thanks for the help as I really want this problem fixed.

Rob

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1987 IROC-Z Auto (LB9)
Black/grey with the stance of a streetfighter

Mods
Custom exhaust. 4 Inch pipe from the headders all the way back to a single muffler at the rear. No Cat.

Future mods:
K&Ns
RAM Air
New Underdrive pulleys-either March performance pulleys or Auto Specialties Performance
Air foil

 

I dont know what you mean by the speedo head but if you suspect different gears then you cn do a very simple check with the car in neutral jack the car up by the rearend and while spinnig the driveshaft count how many revolutions you have to make to turn the rear wheel once. There should also be a tag on the rearend that will identify what it came with stock. I'm also nt sure what the codes are but I know that chiltons has them. Hope this helps!!!

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91 Camaro RS, 305 TBI
No mods yet...Hopefully:
Convert to dual-cat with headers and Borla catback exhaust.
Edelbrock MPFI system.
RAM air hood & Z28 wing.
Z28 cam.
ABS system.
Positraction rearend with rear disc brakes.
Rebuilt front and rearend suspension with polygraphite bushings.
Strutbrace.
Rollbar.