Just bought a 1995 2500 4x4. It was an old work truck so I got it pretty cheap.
I pulled out the plug in the front diff and it was very low on oil. I sucked what it had and looks to have some water mixed in the oil. How much damage will low oil cause?
I guess I will pull off the cover and see how it looks. I can put in 4x4 and roll but not sure if front axle is pulling.

 

I pulled off front cover expecting to see broken parts on the bottom but everything seems like it should. I have never looked at one before. I spun front tire and seems like the gears look normal. What should I check before filling back with oil???

 

spray out the bottom of the case with brake cleaner to clean out any sludge. clean the magnet and check it for any foreign objects. some pasty sludge is normal, just clean that off and put the magnet back in place. wipe out any brake cleaner. use gasket or RTV, either is fine. don't overtighten the little cover bolts. refill with gear oil.

differential gears and bearings are really tough, and about the only thing that kill them is water. the water leaks in past the seals when driving in deep water, so its a good idea to change the oil regularly.

 

OK, thanks. I hope the front end is ok. IThe oil had the milky color from water.

 

That is not really unusual. You will get some over time just from condensation. It takes a while to discolor the fluid though, but then, that seems to be one of the 'neglected' fluids on a lot of trucks.

Clean it out good, seal it back up, re-fill, and smile.

To see if it is actually working, find a dirt road that is fairly wide, lock in the four wheel drive, turn the wheels nice and sharp, and BACK UP. If all is working as it should, the front end should 'hop' a bit when back up slowly. That's normal too. You WILL feel it.

 

I did engage the 4x4 while test driving it. Could not find sandy road around so I tried the 4x4 just to see if anything would bind up while turning. I was able to turn lock to lock with out binding. I have the driveshaft out right now so I have to wait till get new U-joint in. The last Ranger I had got water in the front diff and the 4x4 wouldn't pull anymore. Had to have the chunk replaced.

 

There should be an indicator light in your dash (left of the steering column.) that comes on when the expensive stick is pulled back. If the light doesn't come on, start looking at the vacuum lines for the Central Axle Disconnect system.

 

Yep, light comes on. Was just concerned with being low on oil if that caused any bearing or something to be damaged in the front diff

 

Probably not. Bad bearings and such will let ya know they are bad. Generally by making rather rude noises.

If the light comes on, that indicates the vacuum portion of the system is working.

Put the front end up on jackstands, start the engine, and engage four wheel drive. LEAVE THE TRUCK IN PARK! Try and turn one of the front wheels, the other wheel should turn in the opposti direction. If not.... the E clips on the shaft from the vacuum actuator might have come loose, or, the shift fork in there might have broken. Have to pull the CAD off the axle to check. (four bolts. don't break 'em, pain in the ***. ask me how I know. )