paulbench

Hey all! Long time lurker, finally got around to making an account.
I have a 2007 F150 (4.6, SuperCrew, RWD) with 153,000 on it!
Today I finally changed the rear diff fluid, as I started to see it leaking from the pumpkin. I purchased the truck at 103k, and I am not sure if the previous owner ever changed it. Prior to the service I had a VERY light chatter, usually under 5MPH and not noticeable unless I was listening for it.

I Just changed the oil (To Royal Purple 75w140 + Friction Mod) and a new gasket. Now the chatter is CONSTANT and loud. No matter what speed I'm going or straight/turning there is a very constant metal/metal chirp sound. It sounds like its coming from the rear - which would make sense

I did fill up the fluid until it started spilling out of the fill port, it was performed on a flat surface and I used the proper gasket sealing method!

Any ideas? It's driving me crazy and I don't want to continue driving until I have an idea if I'm destroying my diff.
Thanks!

RLXXI

Use Ford friction modifier.
If it still chatters after that, there's a good chance you need a rebuild.
.

jhelrey

Did you drive in figure 8s? They say to do that after changing the fluid, esp. if you let it drip for a while.

I also second Ford products. I rebuilt my rear end and had issues. When I did the fluid change over to Ford, it all went away.

AlwaysTrucks

I put Valvoline stuff in both of my differentials and transfer case 4 months ago. Theirs doesn't need a modifier and it works great for my 09. Maybe it was the royal purple just not agreeing with your differential, I've heard stranger stuff happening with these trucks. I agree that you can not go wrong with motorcraft though. But if it's really that loud you might need to rebuild it...But if you do rebuild it you could get whatever ratio you want!

techrep

iTrader: (1)

You added a separate bottle of friction modifier.. or you bought the RP with it in it ?