2003 Ford Lightning rear axle fluid

[Revving2Redline]

I helped a buddy of mine modify a 203 Ford Lightning 5.4L. It had a lot of power,but now it had a engine rebuild and port and polish, we added bolt on, the supercharger ported, added Nitrous and other sorts. We adddd Royal Purple ATF too,but is the factory fluid shot or on borrow time. Quarter mile time is in the 11's? The NOS is a 150 shot and fill is M1 5w20? Is the rear end due for service and if so what fluid/weight?

 

[artificialist]

Gear oil is discussed in this subforum:
https://bobistheoilguy.com/forums/ubbthreads.php/forums/16/1/ATF,_Differential,_Trans,_Brak

The factory specified fluid would have been 75w140, but I don't know what should be used when the horsepower and torque are increased dramatically.

 

[buck91]

I'm not really knowledgable on builds like that, but I would image a quality 75w140 would be appropriate. Many here like Redline but I can't comment.

Amsoil severe gear has a great reputation and its going into our Explorer rear and PTU due to extremely low volumes. Motorcraft gear oil is (or was) supposed to be stout stuff as well.

 

[jdavis]

Not sure I agree about running 5w-20 on a supercharged engine with a 150 shot of NOS lol

 

[Colt45ws]

Amsoil Sever Gear 75W140. And put a XW40 in the engine like Mobil 1 0w40

 

[bvance554]

Did you help him rebuild it? Did you and your buddy do the 'port and polish?' You and your buddy have the expertise and knowledge to do that, add on all the bolt on goodies, but you need to come here and ask if your should change the fluid in the rear end? And what you should change it with?

The fluid is probably fine. It won't know you ported and polished the heads and blower.

 

[FranklinJL]

20w in that truck lol. Get some brad penn 20w50 for that motor. I used to own a 1995 Cobra with a custom 502 with 3 kits. 800 hp on race gas, 1300 on the silly spray...ran brad penn in the motor, redline 75w90 in the rear...

BTW I blew that motor up and got our of the nitrous business for good....turbos are the future...

 

[FCD]

I'd say run 15W50 Mobil 1 in the engine and Redline 75W-110 or 140 in the rear end