I was on a jeep trail in my stock 4WD Tacoma in Colo, and had to cross a stream. I doubt the stream came up higher than the center of the wheels, and probably was well below it. The trail is a standard, well-traveled route on a BLM tract. How long does one have to be in that situation, and how high does the water need to be, before it becomes a problem for the front and rear diffs, tranny, and transfer case (I have a manual trans)? I obviously did not linger, and the creek was about twice as wide as my truck is long. It was not raging in mid-August. I guess U-joints are another concern, but I can and will lube those, since they need to be done anyway.