You can fill it right away if need be. I wouldn't drive a long distant right away (don't want fluid to get hot while the RTV is curring)

If you can afford to wait, I'd let it set over night before going on any long trips, but thats just me. I would say 15-30 minutes would do ya fine.

hope that wasn't too late.

 

you dont need to let it dry at all. as soon as you get the cover on filler up.

 

Thanks, I sealed it and waited about an hour while I cleaned up and did a few other tasks. I then filled it with the Royal Purple and let it sit overnight.

So far no sign of any seepage after about 100 miles of local driving. It does seem to be a little smoother with some of the nois gone.

 

^^ Glad to hear it. Its amazing how many people neglect that rear end, until it comes time for a big fix and lots of $$$.

 

Just changed mine out for RP 75w-140 and what a difference. The slow speed shutter is completely gone! I have 54k on my 04FX4 and the fluid was pretty dark, and the magnetic plug had a pretty good amount a sludge stuck to it already.

Now if only I could get this rank smell of gear oil off my hands

 

I changed mine out to Amsoil a couple of weeks ago. At 49k the fluid was black and the clutches were wasted. I'm pretty sure someone had been in there before because it didn't have Ford silicone on the cover and the clutches were stacked wrong. So i replaced and shimmed the clutch packs, filled it with Amsoil 75/140 and I can't believe how much nicer it is to drive now. I probably should have done a spider set too but I had the clutch set lying around anyway and just those took a ton of slop out of the diff. Good luck getting the gear oil smell off your hands, even worse if you got into friction modifier.

 

You people ever heard of gloves?

 

Wash and scrub your hands with lemon juice, its always worked for me

 

Hey PhqChevys I Saw that picture and was wondering if your truck can go faster than what's on the speedometer..just wondering how fast these things go, I don't want to get a ticket finding out for myself.

 

How about passing along the site that has Royal Purple gear oil for $9.99 a qt???!!!!----DirtySCREW

 

The guy at napa said even if using royal purple to go ahead and add the 4 oz of friction modifier because most all differential fluids have friction modifiers in them already.

Truth, or fiction?

 

Fiction. Not all fluids have the modifier in them. I have had RP in my diff for about 15k miles with no other additive. No problems here.

Adding too much modifier can cause problems just like having too little. Use the RP alone to start, and if you get chatter taking corners you can add modifier later. Its much easier to add a few ounces later than it is replace all the fluid since you have too much modifer in there.

 

That pic is actually of the gauge cluster from my '03 Mustang, but my in F150 I have had the speedometer pegged out. I had street tires on it at the time, and you can look at my sig for the other mods. According to the records on my Gryphon, my max speed in the truck is 132mph. That was the point where the engine just couldn't push it any faster, just maintain the speed (max speed). If you are going to attempt this, MAKE SURE your tires can handle the speed, and you are nowhere around other traffic. I was on a deserted desert road going between Las Vegas and Reno, NV...not a thing around for miles. Make sure your truck is up to par, it's heavy, it needs some room to slow down. I need to update my sig, but my truck also has EBC slotted and dimpled rotors and Hawk HPS pads on all 4.

 

That's pretty good for something that has the aerodynamics of a wall, completely stock I imagine 120 is possible.

 

I was TOLD by the service advisor at the local Ford dealer that if I got a tune to remove the speed limiter, my little ole V-6 would do about 125. Do I believe him? I dunno. Do I want to try it? Hell no!