One Ford/Motorcraft 4 oz bottle friction modifier should be fine.

I used to use 80-140 synthetic, Royal Purple, when I had my Traction-Lok. Now that I have an Auburn Pro I use 75-90 dino oil, Lucas, with 8 oz of friction modifier.

Not sure why you are asking about valve covers but I like the Moroso ones.

 

When I had my truetrac i had to run dino fluid. But now with my eaton posi (lsd) i use RP synthetic 75-140. 2 quarts and a bottle of friction modifier. As for the diff cover, i use an lpw cover.

 

Oh, I thought he said valve cover. Any one should do as long as it has the carrier support bolts. Some may or may not need a pan hard relocation. I have the Ford Racing one.

 

Oh, I thought he said valve cover.

Yeah I did, typing and not paying attention :dunce:

Are the girdle support caps that big of a deal? I figure my car will never see a supercharger.

I'm guessing I need a panhard relocation bracket for most of those aftermarket covers, eh?

 

He did say valve cover but the boss doesn't have finned (heat sink) valve covers, it has a diff cover lol

 

Lol. First thing I thought of were those old school Mickey Thompson valve covers.

http://m.ebay.com/itm/251439758477

 

I'm running 75-140 Amsoil in mine, no complaints. Also have the Boss cover. You can pick one up from Tasca for about $60. One bottle of Ford friction modifier is all you need. And if you're like me and suffer from a habitual leaking axle vent, I can recommend the JLT axle catch can.

 

Redline 75-90 NS here. Torsen recommended whatever the factory fill is but after some reading on the tech with the T2R, the heavier oil was dropped in favor of a lighter oil for the higher bias ratio. 75-140 would drop the bias ratio almost a half point. Same with friction modifier. The original Torsen diff was designed to work in ATF...

 

When I put my T2R I was very tempted to use 75-90 with the same reasoning as Whiskey11 gave. However, diff oil operates under one of the most harsh conditions among all car fluids without any explicit cooling system designed for them. Thicker oil means more pressure within diff and more heat. So unless you are opting for a better diff cover with finned option for better cooling, not sure if it is worth taking the risk of using 75-90. I have seen one guy smoking his T2R with 75-90 in an autocross course! Diff oil stinks anyway, a burning diff oil is like attack of thousand skunks

 

For me, it's Royal Purple Synthetic 75W-140 Rear Gear Oil with a separate bottle of Friction Modifier, and a Low Profile Ford Racing Differential Cover with Load Bolts and Fill/Drain Plug

 

iirc oe fluid is 75-90, the thicker viscosity lead to chatter in the oe lsd. The tsb was to switch to 75-140. Op my LPW cover fits without modifications and has the support pieces, its just not as pretty as the ford racing one

 

Offchance does anyone know how long the bolts have to be for an aluminum cover, in case I get one that doesn't have a bolt kit?

Also I didn't think TA-style covers with the girdle would clear the panhard.

 

I used 1 1/4" long bolts for mine.

 

Something else you may want to pick up is a cheap pump action weed / garden sprayer (the type with the canister and spray wand). It's the best $7 I've ever spent in terms of not seeing diff oil drip everywhere when trying to squeeze fluid into the fill hole.

 

You know what I did? Removed the vent and filled from the axle tube. Less mess and works just as well. Got to pay attention to the fill hole still but it isn't bad.

 

So should I use 75W-140 instead of 75W-90?

I got a $25 rebate from Advance Auto Parts from when I ordered my spark plugs, so I'm gonna buy the oil and diff cover soon, planning to do this job in the next couple weeks. Spring is fast approaching so I'm trying to get all my little projects wrapped up.

 

Damn so many different opinions, when I did my gear swap 600 miles ago I heard 75/90 non synthetic because it was thicker!!! Now you good folks are telling me 75/90 Full Synthet? Which is it?!? I'm about to change my rear end oil tomorrow as well please help!

 

The factory fill is 75W140 so you are always safe picking that.

 

Get a can of Brakleen, a scraper and a tube of Ultra black rtv too. Scrape the diff housing clean and wipe it down real good with Brakleen. Apply a bead of rtv. If you do install a diff cover with a girdle either use copper washers behind the lock nuts or apply the rtv behind them because they will often leak. Also, check the drain plug on the new cover if it has one. They never tighten them.

 

How much oil is it supposed to be? Ford racing says 3 quarts iirc, some people say fill till it leaks out the fill hole (which won't work since having the rear end jacked up will tilt the axle).

And then someone on the first page (maybe bigchris) said 2 quarts. What is the real actual fill level?

 

Up around the side on the driver's side there is a plug. You have to use a 1/2' drive to get it out. Pour it in the fill hole on the cover until it comes out the hole on the side. Do not fill it to the bottom of the fill hole. On most covers that is way to high. If you want to eyeball it it should be level with the center of your axle shafts.

 

Not stupid, just slow. lol.

Actually I should have been more clear. I forgot the factory cover does not have a fill hole. In your case, yes, fill it till it comes out your fill hole.

 

So I took off the plug and there was a vacuum in the diff. Why was there a vacuum?

 

Because when it heats up it expels any excess pressure out the axle vent check valve. When it cools the vent won't let anything in so it forms a slight vacuum. That is actually a good sign. That means all of your axle seals and such are in good order.

 

No, I'm saying that the axle would tilt forward when you have it in the air. Like how the oil pan can tilt back when you jack the front up.

 

So level the car out? with the weight of the car on the axle you should be in that 2º range with pinion angle (usually negative) which is next to minascule and or not important when filling diff fluid up.

When I dumped my rear diff fluid after the 500 mile break in I just put the front up on jack stands and the rear was supported by my ramps. Close enough to be honest.

 

If that's all the difference then I suppose it wouldn't really matter.