Change The Differential Lubricant Or No?

[jbeall]

The manual for my 2003 Yukon XL says to "Check rear/front axle fluid level and add fluid as needed. Check constant velocity joints and axle seals for leaking." Two initial questions:

 

1) This is talking about your differential, right? I think of an "axle" as being a very different thing (a simple rod between the wheels) and the differential (which is a gearing mechanism to deliver variable amounts of torque to wheels). But, on page 5-47, it has "Front Axle-When to Check and Change Lubricant", and in there is says "When the differential is cold, add enough lubricant to raise the level to 1/2 inch (12 mm) below the filler plug hole."

 

This, and the fact that nowhere else is the differential mentioned in the manual, makes me think that these references to front and rear axle fluid are a reference to the differential fluid.

 

2) Is "check[ing the] constant velocity joints and axle seals for leaking" as simple as looking for lubricant fluid on the joint and seal? If not, what do you do in order to ensure that the joints/seals are not leaking?

 

 

 

Now, on to the question that really brought me here--how often, if ever, do I want to change the differential/axle fluid? My Yukon XL Owner's Manual from GM only mentions checking the level, and adding fluid if it is low. Nowhere in the scheduled maintenance list does it mention changing the fluid. Apparently they did, once upon a time, suggest changing the fluid, because you can see they discuss in on page 5-47, where it says "When to Check and Change Lubricant." However, it goes on to say that you see "Scheduled Maintenance Services on page 6-4," and when you go there, it only says to check the levels, never to change.

 

This is in agreement with what the local dealership that I got the truck from says--now that they are using synthetic lube for the differentials, they never need to to change the lubricant, they just check the levels and add if necessary.

 

The transfer case is similar. You check the fluid level every 12 months, but you never change the fluid.

 

However, my Haynes manual tells a different story. It says to change both the differential lubricant, and the transfer case fluid, ever 60,000 miles or 4 years.

 

The consensus from my reading on these forums is to change all your fluids.

 

I thought I'd get some feedback on when and why to change the fluids. E.g., who do you think is wrong, and why? If GM is wrong, why should you change the fluids? If Haynes/et al is wrong, why shouldn't you change the fluids?

 

-Josh

[brims]

The axle housings are directly attached to the differential housing, so changing the axle fluid is the same thing in these trucks, may not hold true in some exotic vehicle, I don't know. But they just refer to it as the axle.

 

I changed my fluid around 15k just to get anything out that I don't want in there. My new cover leaked 2 other times so was forced to drain and refill.

 

If you drive through mud and water I think it's recommended that you check for water in the differential fluid. You really don't need to change the fluid from what I gather. But doing it can't hurt. If you do it at 60k then you should be good to go for a long time.