231 transfer case, 3.55 rear diff ratio. 31" tires.

I don't know if 31 or 32 tooth gear is what I need. I've seen charts and posts suggesting both.

Need some help, thanks!

 

32 short shaft

http://www.ruggedridge.com/speedomet...-18760-13.html

 

Thanks^^

 

Hi same question from a slightly different angle....I have read the charts...31's need a 32 tooth gear...I have Brand new 31X10.5 Revos...With the weight on wheels my 31 Revos only measure 30 inches. I have measured all 4 wheels accurately and they all measure 30. SO...is the chart based on actual measured wheel size or manufactured stated wheel size...if anyone knows...Thanks

 

I just took a long trip in my jeep and had a tom-tom gps hooked up. At 60mph speedo reading I was reading 63mph gps speed. I was able to get a fairly steady speedo reading and had time to let the gps equalize and it was a fairly consistent 3 mph difference. I did this numerous times. My math says 3 mph difference at 60 mph equals 5 % off. I was running 31X10.5 Revo's . The charts say 31 teeth for the calibrated gear for these tires even though they only measure a true 30 inch diameter...brand new. I just removed the gear installed and it says 34 teeth so I multiplied by .95 and got 32.3 for the new gear to equalize so I guess I will be getting a 32 tooth gear...Is my calculations accurate or is it not the simple formula that it seems..It probably doesn't matter too much whether its 31 or 32 teeth but I try to be accurate

 

WELL...I misread the chart and it appears my math matches the chart after all so it is a 32 tooth gear that I need