Can anyone tell me for sure when the gear lube in both differentials needs to be changed?
Thanks,
JDGMC

I would say change it at around 1500 miles. Look at the fluid closely to see if there is a lot of metal or even some chunks.

Ditto what akdiesel said.

And at the very least follow the OEM manual after that until they get dmaxallitech's (Eric's) Recommended Maintenance Schedule posted again. It should be in the Maintenance Section soon.




Gary

Has anyone made a step by step directions for changing the rear and front differential fluids. Or where can I find how to do this proceedure.

Very simple.
Just like the transfer case drain and refill steps.

To check level - Pull top plug (usually on the back side of the pumkin or the case) and check for level. The level should be just even with or slightly lower than the opening.

To drain - place drip pan under the area and pull lower plug (should also be right below the fill plug and on the same side), drain out all of the liquid. Look for any metal or pieces that may come out. For a better inspection pull the cover off and look at the gears as well as the lower part for any chunks.

To fill - reinstall cover if removed with a 1/8 beed of gasket seal or a new o-ring and torque bolts to specs. Reinstall drain plug. I always use teflon tape and make sure that there is no tape on the surface of the plug that will be inside the casing. Torque to specs. Try to make sure the truck is level because too much liquid can cause foaming action. Fill the case with the correct liquid/weight by squeezing the bottles into the fill plug hole (the hole used to check the level. Most if not all bottles are designed to be able to do this type of method. They also make a pump that you can attach to each bottle to make it easier and cleaner. To worry about over filling the case since it will just run out untill it is level with the hole. This is a good idea to do since you will know where the level is alot easier. Tape plug and torque to specs.

Note: On some transfer cases I was told that there is some metal disimalarities, like magnesium, steel, and alluminum. Make sure you use the original plug or get one that is a direct replacement if you need a new one. Or you can quickly corrode the material.