dloudy

For some reason, I got one hell of a roar in my rear differential. I figured I would check the level and change it out if needed. I notice the rear calls for friction modifier and the front uses a different weight.

Any recommendations on brands, modifier...or can I go without modifier if I go full synthetic?

Thanks for the input.

truckbed

the book calls for full synthetic so i hope its not an "IF i go full syn..."

some guys swear by motorcraft (although i think they get a kickback for every time they say the word) and others like royal purple as it has friction modifiers already added.

Mod (Ret.)

I don't think it's a "kickback" as much as it is convienience. Motorcraft is readily available, and takes any guesswork out of what's acceptable and/or compatable. Royal Purple is great stuff, but not available on the shelf at all parts stores. The Ford dealership in Lewisville Texas offers Royal Purple as a substitute for Motorcraft semi-synthetic engine oil; I was suprised they did this.

The folks at your Ford service or parts department can provide you with the need information on fluid compatabilities for those who don't have a repair manual, or an owners manual.

truckbed

sorry dude, i trust 0% of dealerships. they told me my truck does not have a pcv valve. i insisted that it does have one and he finally decided that it has one and it cannot be replaced, which it can. you people on the internet know more about these trucks than the dip****s who put them together. well, some of you do!

dloudy

Well...it wasn't really an "if" I go synthetic.....
I just noticed in the manual that it called for different weights in both the front and rear.

Once upon a time, I ran redline in my mustang and had no problem at all, and didn't have to add friction modifier.

I had the pinion seal replaced in this truck because it was leaking not too long ago. I hope the dealerhip had enough sense to top it off with fluid, but then again...we are talking about a dealership here. Now the rear end has developed a roar, and you can hear the gears "meshing" together and whining, if you will.

I thought it would be a good idea to go ahead and change them both out (front and rear) with some good fluid so I know it's good to go....then see if I have anymore "roars" or other problems.

truckbed

i think thats a good idea too.

go dawgs!

dloudy

Any suggestions on what route to go in terms of brand of fluid? I know you guys mentioned Royal Purple and motorcraft earlier.....but around here, I'd be striking gold if I found Royal Purple.....and the Redline, Amzoil, etc., is special order.

The dealership can kiss my *** on ordering Motorcraft.

Advance and places like that usually carry Valvoline synthetics from what I've seen, and Wal Mart might have a Supertech synthetic or two.....

What have you had your best luck with?
Thanks!!

nightridr

hey dloudy, did changing the fluid get rid of the "roar"? I started hearing that noise recently and was debating whether or not to change the fluid. thanks

golden-lariat

I believe the friction modifier is for the LSD. I changed the fluid in my truck when i got it. We used synthetic but no friction modifier. Now its kinda turnin in to posi. Which works for me!!

Mod (Ret.)

Well "dude", you need to locate another dealership. As I stated, the dealership in Lewisville Texas knows their stuff. I have no problem driving in, talking with a service rep or parts guy, and getting the answers I need; correct ones.