If you are refering to taking your mog through the water. You don't have to change the dif fluids. The dif vents go up under the hood, so you shouldn't have any problems with getting water in the diffs. I believe they actually vent into the air intake somewhere(before the filter), so if you have a snorkel you can even go right under without getting water in the difs.
Gotta love how water proof the mogs are.
Reg trucks like mine usually have the difs vented along the fram rails, so if you get water up that high you should change the fluids.
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Coquitlam Crawlers
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1974 Dodge W100 Power Wagon BROKEN
Looks beaten up but it's fun.
360 V8, TF-727, NP-205, D44 front, chrysler 8 3/4" rear with detroit locker
http://members.shaw.ca/jaretthumphrey
[This message has been edited by Jarett (edited March 03, 2002).]

Reg trucks like mine usually have the difs vented along the fram rails, so if you get water up that high you should change the fluids.
------------------
Coquitlam Crawlers
------------------
1974 Dodge W100 Power Wagon BROKEN

Looks beaten up but it's fun.
360 V8, TF-727, NP-205, D44 front, chrysler 8 3/4" rear with detroit locker
http://members.shaw.ca/jaretthumphrey
[This message has been edited by Jarett (edited March 03, 2002).]