stole this from a different thread on R/F. its a list of things to water-proof your truck.
"Very true. I cross deep water frequently, but you need to do it knowing what you're facing both in terms of what you're crossing, but also what some of the potential side effects are. Here's some things to remember and some may add to it if I don't note something important:
1. You need to extend your axle, transmission, and transfer case vents up to a higher level. Top of the engine compartment with "reverse traps" (that is, with the tubing bent over so the ends point down) is a good spot.
2. If you go through really muddy water, you can get it packed up in your radiator. Make sure you check it when you're done.
3. If you have an older Ranger with a distributor, that's a really important item to keep maintained and waterproofed. Later DIS ignitions are quite immune to water, but if your wires and boots are crap you can still get shorted out by water. Keep your wires in good shape.
4. Axle, driveshaft, and pinion shaft seals will leak when immersed in deep water sometimes. They weren't really meant for the externally applied pressure of deep water. After you've done some crossing, open your fill plugs and get a sample from the bottom of your diff/tranny/tcase using a tube of some kind. Particulary important to check are the front locking hubs and grease in the spindle. Periodically renew your seals. I do mine every year whether they are bad or not.
5. One more item I think needs to have the vent extended: the charcoal cannister purge inlet. If your engine goes into purge when you're underwater you'll suck water into the charcoal cannister and possibly foul it and the purge valve. This can cause leakage and an inability to pass emissions tests if the emission related drive cycle monitors are checked. You won't be able to hold a vacuum in the fuel system then.
If you want to cross deep water with any regularity you need to have an "inspection program" or one day you're gonna' get bit by a large repair job."
