Which rear end?

it depends on what kind of driving you`ll be doing more of; city vs. highway. also, what is the HP output of your engine? and don`t forget tire size as well. MANY things have to be considered for getting the best fuel mileage possible. oh, and how heavy your right foot is as well.:)

in theory 3.42 will give the best mileage, however in practice sometimes a deeper gear like a 3.73 will give you better mileage as you don't have to get as deep into the peddle to get going. if you run empty all the time, get a 3.42, if you actually put something in the bed and tow only occasionally, get a 3.73, if you tow more than occasionally, get the 4.10.

a limited slip uses clutches ( or gears, if a torsen type) to literally limit the slip that a tire can achieve on limited traction surfaces. they work fine on the street, don't work at all off road.

a locking differential (ignoring the selective lockers) is actually misnamed. they actually are automatic unlockers. in a rest state, the axles are locked together like a spool. however, in a coasting turn, the locker will allow the outer wheel to overrun the inner wheel. if you go into a turn and remain under power, the locker will not unlock and understeer will result.

HTH, Bret

Which series? It sounds like you're looking at a 1500 4x4. If so, you probably are looking at either the 4.8L V8 or the

5.3L V8. If the 4.8L then stay away from the 3.42, it will shift down too much on small grades. If you are going to tow anything, I'd go with the 4.10. From what I've heard the difference in mpg isn't much between the 3.73 and the 4.10. In any case, don't expect much for mileage. My '96 Sierra 4.3L V6 got 21/22 mpg solo on a trip (3.42) and my "old" '02 Sierra 4.8L V8 (3.42) got at best 16/17. Was sorta disappointing. HD in NY