Flushing your differentials..
If you ride in mud and water, you know that it can eventually seep inside your diff and turn the gear oil into what looks like a thick milkshake.
It's a good idea to check the gear oil in your diffs often. If you find any signs of water or mud, you'll want to flush it out and get clean gear oil in it as soon as possible.
To flush your diff..
You'll need gear oil (a quality 80w 90), gallon or so of diesel fuel, a funnel with a hose or a transfer pump to add diesel and gear oil, and a drain pan.
Step 1. Pull the drain and fill plug and let the oil and water drain out. Screw the drain plug back in.
Step 2. Using a funnel with hose or a fluid pump, fill the differential with diesel fuel until it runs out of the fill hole. Then screw the fill plug back in.
Step 3. Make a lap or two around the yard not going very far or very fast, just enough to get the diesel to work around in the diff.
Step 4. Drain the diesel out into your drain pain. For really dirty diffs, you may have to repeat steps 2 and 3.
Step 5. With the drain plug and fill plug still out, using that same funnel or transfer pump, add gear oil until it starts to run out the drain hole, then replace the drain plug.
Finally, fill the differential with the appropriate amount of fluid, (usually just below the fill plug).
Pro tip.. if you are getting water in your diff every ride, take a look at the seals on your diff where the axles and driveshaft go in. They could need replaced.