WOW, I knew there would be a difference but not this much!

I'm on 30x9.5 BFG A/T right now and before with the 4.30:1 stock gears the speedo read 3-4 mph less then what I was traveling. NOW, with the 5.125 gears, it reads 9mph fast at 60mph.

It gets up and goes faster tho and with it reading wrong the TC locks up still at 47mph per the speedo reading but only traveling 40ish mph so driving around town the rpm will be lower but highway looks like 60mph will be about the max running the speedo around 70mph and 4k rpm.

Is there anyway to run something to make the speedo/odometer reads correct so it doesn't run my mileage way up?

Time for some 32s or 33s to offest this some!

Ya, put in the manual trans speedo drive gear, it will then read closer to correct

Wild

before with the 4.30:1 stock gears the speedo read 3-4 mph less then what I was traveling. NOW, with the 5.125 gears, it reads 9mph fast at 60mph.

sent you message about your 4.30 gears....

You have to change BOTH speedo drive gears, the inner one is on a shaft in the t case which requires removing the back of the case.

Ohh, I didn't know about that, both gears looked the same to me 

I thought the answer was to install the GPS and ignore the speedometer. 

I thought the answer was to install the GPS and ignore the speedometer. 

Eh, traveling 60mph the speedo reads just shy of 70 mph... but around 4k rpm IDK how much highway driving I'm going to do with it till I get some 32 or 33" tires to offset it some.

I just swapped a t-case from a 3 spd auto (4.6's) into a Kick that ran 4.8's from the Factory and the speedo didn't work as the gear inside the t-case is too small a diameter to engage with the drive in the end of the speedo cable. Swapped the drive and it now works fine. The 5.12 geared Kicks have the same size speedo cable drive as the 4.8 geared ones so that hasn't been a problem swapping between them.

I thought the answer was to install the GPS and ignore the speedometer. 

I'm with that, and really, just drive the tach. You do get used to it though, when mine reads 57 I know I'm going 65, 62 is 70, and after that I'm too busy trying to watch the road!