I am in the process of changing my rear differential fluid on my 2009 1500 SLT, just wondering what weight of oil to use, i called my dealership and they said to use 75w-140 synthetic gear oil is this correct?

 

thats correct

 

thats correct and if you have the 3.92 with lsd differential you need to add a friction modifier additive 4oz or get the gear oil with it already in it if you have the 3.21 or 3.55 you just need the oil

 

Why are you changing your differential fluid?
Did you go thru deep water?
I ran my F150 111,000 miles and never needed to change it.

 

Some people like to change it every 20k or so. IMO its a waste. I'm changing mine at 100k miles. I've never had nor do I know anyone with dff troubles related to late fluid changes.

 

The scheduled service calls for changing it. In order to maintain your warranty you probably need to follow the schedule.

Is 30K too soon? I'd think so. I've had other vehicles that have been able to do 60K or 100K between diff fluid changes. I'd say 50K is probably enough, and after my warranty is up I'll switch to that.

Rob

 

Thats why, thanks everybody for your help going to buy some royal purple, and be done with it.

 

In my old GMC with an LSD, the maintenance required the first change at 15K miles to get rid of the friction plates break in impurities. I don't remember the schedule after that.

 

The scheduled service isn't clear when to change it. The manual says every 16k miles if you tow alot, otherwise just check it.

 

I guess I was confusing it with my Grand Cherokee which was every 30K regardless of use.

Looks like spark plugs are the only semi-regular maintenance item (other than oil changes and air filters).

Rob