Engine/Transmission (1998.5 - 2002) Differential fluid changes

[Adam]

I'm sure it's in here already, but I can't find it, so here goes...

I know I need to run my engine 10-15K before swapping to synthetics, but how long do I have to run the factory stuff in the diffs before I can swap to synthetics and get that easy rolling, high-mpg feel? I don't want to rush things, but as the temperature drops (-3F as I type this) I'm starting to feel the truck coming to a halt a little more abruptly than it used to when I'm coasting to a stop. It also takes a good while longer to achieve my cruising mpg upon initial start-up.



TIA,

-Adam

 

[LSMITH]

My rule has always been 500 miles on a new diff. Now that I am thinking about it I am not sure where the 500 miles came from, but I think it was from a gear set maker. 500 miles is enough to break it in good. Most of us need a couple years to get 500 miles on the front diff, but since it is used rarely and only at lower speeds I would change it out right now as well. My front diff has quite a few miles on it, but I use it in the rain quite a bit and things like that.

 

[klenger]

I changed mine after a couple of hundered miles. I used Amsoil 74w140 (I think that's the correct term. Too early in the morning) and installed a Mag-Hytec cover. Love it.