Need help with Speedo gears. I have an 87 IROC 5.7 automatic with a 9 bolt. Changed 3:27 gears to 3:73. I have stock tires. What parts do I need to adjust the speedometer?
Thank you,
Arty

 

JMD on this board can fix you up with all that you need. Do a search on his name.

JamesC

 

I sent JMD a personal e-mail asking for his help. Thank you for yours.

 

Anyone else that can help?
Thanks,
Arty

 

Ok, I can only assume (for now) that you have a mechanical speedometer and stock 25.6" tall tires. If anything is different, please let us know, it will influence the gear selection for your speedometer.

If you have the purple 10-tooth drive gear, you will need the green 29-tooth driven gear (#25524924).
If you have the white 13-tooth drive gear, you will need the blue 38-tooth driven gear (#25522483).

If you have the red 17-tooth or yellow 19-tooth drive gear, you will need to change it to one of the above drive gears. There are not driven gears that would match these to give an accurate reading. The part #'s are 8628838 for the purple 10-tooth drive gear (I know who's got one for sale) and 8634934 for the white 13-tooth gear.

Hope this helps.
Lou