Speedometer gear for 4.88 ratio

[myjeep3]

My 97 TJ speed is about 10 mph off, it reads about 70 mph on dash while the gps is only at 58. I read that i need to replace the speedometer gear, base on some chart I looked at, i need a 38 gears. Is that right? Where to buy the gear

I have a 4.88 gear ratio and running tire size of 315/70r17.

Also my transfer case if leaking somewhere, not sure if its related to the above.

 

[Jerry Bransford]

That's roughly equivalent to a 35" tire so I'd go with a 39 tooth gear. Those gears are available on Amazon like at https://www.amazon.com/dp/B00EDWLLYU/?tag=wranglerorg-20

 

[inkedrose]

I used a speedo healer on my 04'. A little more expensive but pllug and play. Can change it up as often as you want for gear, wheel, tire changes, ect.. 15 minute job

https://www.polyperformance.com/hea...MIr7O27oWXgwMVbhmtBh3JWAl2EAQYASABEgIau_D_BwE