05 SD Which Limited Slip??
Rear axle: Ford 10.50" full-float, made by Visteon.
My truck, though older, is similar to yours: '92 F350 SRW CrewCab 4x4 longbed. I also use my truck in sand in the California desert, as well as for hauling a camper and pullling a trailer with dirt bikes for weekend fun. Mine came originally with regular open differentials front and rear. The truck's off-road traction was rather embarassing, even with good tires (BFG AT's) and dropping the air pressure.
I opted to put a Powertrax Lock Right auto-locking differential in the rear axle and am quite happy with it. It's a completely different truck off-road now. The truck will go alot of places in 2wd now that previously required 4wd and when I put it in 4wd, it claws it's way through pretty much wherever I want to go with it
. The Lock Right differential is a locker (like a Detroit Locker), which may or may not be something you will like. Lockers make a little clicking and clunking noise and chirp tires when you get on the gas. You can find out more about it by checking out the manufacturer website: www.powertrax.com.



