When people get 4.88's or 5.13's, is that a single gear in the rear end, or is that an entire gear set in the transmission?

 

Thats the gears in the front and rear axle. You WILL have to change both front and rear gears at the same time. You could also just gear the rear and NOT enguage the 4wd then get the front geared or vise versa.

 

So since I have the 4 speed auto, each gear 1 - 4 is multiplied just that much more over 4.10 going with 4.88 or 5.13?

 

Yes. That's how it works.

 

I would also suggest that if you do only the rear to go ahead and just pop the front drive shaft off too instead of soley leaving it just in two wheel drive (anybody correct me if I'm wrong please) but I'm pretty sure that if you leave the front drive shaft on and your running two different gear ratios between the front and the rear both are going to be rotating at a different ratio and speed and both being connected to the T-case will cause issues. Just my 2 cents and what I thought but dont take my word without further research I am far from an expert on drive train.

 

True. This could cause binding somewhere in the driveline. My front shaft is off cause my front is 3.73 and my rear is 5.13.