Thank you all for the information. Like I said I am no mechanic, but I love to tinker with my truck. I think I understand about the 7.5 and 8.8 thing. It's is the size of the "guts" in there, right? The 3:73 or 3:45 is the ratio of the gear sets(?) to each other? And after reading these replies I think L/S is the way to go if both sides spin at low traction/speed. If only the right side spins with an open type and that is the side that has low traction (snow or mud) what good is that?

Is there any general rule of thumb on how far off the speedometer will be? Is it something that can be recalibrated and how much of a PITA might it be?

Thanks again for helping out this noob.

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Little Black Ranger: R.I.P Born-1997 Died-2018. 297k miles of good times. You will be missed.

Oh Deer: 2003 XL 2.3L 5-speed stick w/OD. Current mods: Body work after hitting a deer 12 hours after I bought it. Averaging 32 MPG on the highway.