i need some help from your veterans. my car's speedo was setup for 2.73 gears and 235/60/15 tires. im swapping in 3.73 gears and 275/50/15 tires. i know summit has the gear calculator, but i was having some issues for it. im going to guess i need both the drive and driven gears? its an 86 700r4

 

I went thru the same ordeal, but NOTHING fits my tail housing. (something about a th350 where a 700r4 should be, but I cant identify the tail housing at all, anywhere) Try TCI automotive, these guys live and eat gears and transmissions. They will tell you exactly what tooth combination's you need.

 

http://www.700r4.com/speedoCalc/speedocalc.shtml

 

awesome, thanks