Mine did that. Found it out trying to cross a flooded stream.
Tighten the belt. Even if it seems tight, tighten some more. If that doesn't help, replace.
95 Laredo 4.0, 2" RE BB, RC N2.0 Shocks, Custom Roof-Mount Light Bar w/ 6 lights, Bumpers deleted, Homemade sway bar discos, Michelin LTX 31x10.50s, and a Dog Box :)
Planned: Homemade Spare tire carrier, double shear front track bar, 4 adjustable rear control arms, New Rims and 33" Wrangler MT/Rs or BFG M/T KO's w/ LOTS of trimming.