speedo gearing..totally confused

[Teds89IROC]

I swapped from 2.77 to 3.42. Just called chevy asking them which gears I need for the speedometer. They told me 15 tooth drive gear and 41 tooth driven gear. GM no longer makes them and I need to go aftermarket. I looked on the site that Bill posted up in my last post and the only drive gear to accomodate a 3.42 rear is 17 tooth, not 15. Is the stock drive gear in an 89 700R4 17 tooth? Also, what is overal diameter of a 275/40/17 tire? or stock iroc 16" wheel/tire?

~Ted

[Tru2Chevy]

Stock 245/50/16 = 25.6"
Current 275/40/17 = 25.7"

http://www.miata.net/garage/tirecalc.html

- Justin

[Teds89IROC]

ah awesome, thanks Justin. Also found out a number 45 driven gear will work with my tranny :-D

~Ted

[NJSPEEDER]

http://www.tciauto.com/tech_info/speedo_gears.htm
this is the most accurate calculator i have found and it also has reference charts for what gears are available and part numbers :)

[Tru2Chevy]

http://www.tciauto.com/tech_info/speedo_gears.htm
this is the most accurate calculator i have found and it also has reference charts for what gears are available and part numbers :)

So no gears available for the 700R4 for anything over a 3.73? That's crap...

- Justin

[alamantia]

i did th esame swap in my 91 camaro, the gears are color coded. If i remember correctly the drive was gray and the driven red or th eother way around and GM still stocks them.