What do I need to order to change the rear diff fluid on my 2012 FX4?

I want the best.

Thanks!

 

Same stuff it's been for many years now - 75W140 full synthetic for the rear and 80W90 conventional for the front. 75W90 synthetic is okay for the front. If the rear is limited slip you need a bottle of Ford friction modifier, the e-locker doesn't need additive.

 

What he said about full synthetic. I used valvoline with the correct amount of friction modifier. I bought the friction modifier of Amazon. Be warned it smells like *** so use gloves. I have an XLT without the E locker though. Just check your manual. It was a pain to do without a drain plug though, I used a suction gun to remove the old stuff. But if you have the money get yourself an aftermarket diff cover with heat fins and a drain plug.

 

Any particular brand you guys recommend?

I'll check my vin, but I think I've got limited slip and an e locker.

 

You have either a limited slip or an e-locker - not both. Limited slip needs modifier, e-locker does not. The VIN won't tell you, but what's the AXLE code on the door jamb sticker?

Any brand of fluid is fine, but you should use Motorcraft modifier if you have a limited slip. To do it right you need to remove the cover to drain the fluid, a suction gun won't get all the crap out of the bottom.

 

Sorry for the late reply.

L6 is the axle code.

 

L6 is a locker axle. you don't need friction modifier because it doesn't have slip clutches, but if the fluid you buy has it already in, it's not a problem. I would suggest ford's 75w140 gear oil or Redline's 75w140 fluid. Redline's has a higher amount of ester base in it which doesn't sheer in the same way as conventional fluids, even type III "synthetics", but Ford's fluid is good too. you will need to buy 3 quarts as it requires about 2.6 to fill. You will also need to clean the gasket material off the cover and axle and then re-seal with a gasket maker. I would suggest permatex gear oil gasket maker.

 

Screw RTV. Use a gasket.

 

You're right about using a suction gun not getting all the crud out. BUT I just did that for temporary purposes. I had my rear end rebuilt after the dealership screwed it up after incorrectly installing the flange that was causing a noise. Oh get this. The dealership used some sort of sealant on the rebuild. Don't know if they also used a gasket though.