I've been concedering changeing over to a synthetic "oil" in my transfer case, and diff's. Is there any problems that anybody else has encountered? Is there a concern about the residual oil when the synthetic is installed?
D1, 147,000 miles.
Rich

With 147,000 miles I don't think there is much need to go to synthetic. Just make sure that you change the diff fluid somewhat frequently if you offroad with water crossings.

Do you still need to "change the diff fluid somewhat frequently if you offroad with water crossings" if you install higher than normal breathers?

Chris,

The higher breathers will minimize the potential for water ingress into the diffs, but won't eliminate the possibility entirely.

--Craig

Got breather tubes, and agree, "trust but verify".
Still courious though, is there a process for converting to synthetic?

Drain the old stuff, and pour the synthetic stuff in. It's my understanding that it is ok to mix regular and synthetic oils.

if you want to feel real good about it, run it for 1000 miles and change again. that should get most of it out.
or just leave it in the driveway for a month and let all the old stuff leak out.

Nothing like a self purging system!

Rich, synthetic oil and conventional oil are completely compatible. The diffs in these trucks are pretty tolerant of just about any kind of oil and the bearings will do fine as long as the oil is clean and there is no water. Save your $$$ for other maintenance. I think a common perception is that you can keep synthetic oils in there longer, but for the diffs that isn't the case. Conventional won't break down before contaminants get in there, so I think synthetic oil is kind of a waste, at least in the diffs.