Well let me say first that I am talking about a 1996 Ford Bronco 4x4 (there is no form for broncos) Well my problem is when I step on the gas there is like a loud roaring noise from the rear end and when I let off it stops, it only does it when there is torque on the rear end. A shop said that it is a gear in the diff but I can't remeber the name but it started with a "P". If anyone knows what it is and how to fix it please write back. Please! Or even if you know what it is.

 

pinion gear.....Ring and pinion... as far as fixing it is not a do it your self endevor. Pull the drive shaft, booth axles, rear brakes, shoes and drums, Diff housing ect...Ring and pinion come in a set, you will need new axle seals and you have to adjust the back lash...

 

Crud that is alot of things but oh well we will put up with it. Also i know this is a little off-topic but, where is the breather filter on my 1997 Ford F150 4.6L? Thanks

 

I would of guessed the same, the pinion gear is making noise with the ring gear. One way of checking is to take off the back cover and see inside, seeing the wear pattern if something else doesn't tell the story. Sounds familiar though when they don't mesh right, they have a tendancy to whine even, under load.

 

as in air Filter ? Round canister right side fender metal hasp you undo, canister slides out..
IF PCV breathier right side on valve cover..looks like a plug...

 

No not air filter, breather filter. The motorcraft website said I had one so I wanted to change it.

 

I was also wondering if i could put some better fluid in my rear diff to calm down the noise? Mabey lucas oil treatment? Mabey instead of 75W140 putting in a higher #?

 

If it's that loud, whatever damage that's done is done. Ain't no band aids for it...you're gonna have to tear it down and see what all's screwed up.

 

Indeed, there's no living with it. Once it's damaged, it's not going to heal itself, and will get progressively worse. Fix it ASAP before it destroys other components in the axle.

-Joe