I have a 99 XJ with a RE 5.5 lift. I have configured that the speedometer is between 8-10 mph off. I know they make a small gear that can re calibrate this. Does anyone have experience with it? Does it work? Worth It?

 

Yes it works. Yes its worth it.

Unless you just use GPS.

 

Easy install? Does it mess anything else up, such as cause any lights to light up on dash or anything?

 

You gotta pull the tcase and bla bla bla, so not for the light hearted.

No lights to come on and yell at you. I have a speedometer shop in my area, so I'm lucky.