I apologize if this question has been asked before, but I couldn't figure out the search words to find it...

I have a '78 F150 with axle code H2J; I understand this to be a Ford 9" rear axle. I'm trying to figure out how you check the rear diff fluid level, or even change the fluid. Any help is greatly appreciated.

 

these axles are great for strength, TERRIBLE for convenience.

yank the wheels and rear brakes, unbolt the axle plates and slide the axles out. drop the driveline and unbolt the carrier. replace the seal and bolt the carrier back on when the fluid is drained and wiped clean. fill up to the fill plug.

 

The level is check through the fill hole. On the drivers side of the differential housing there is a 1/2" pipe plug. Remove the plug, oil should "dribble out" of the hole, if it doesn't add oil till it does.
Some (very, very few) have drain plugs. You can try a suction gun or, as bobwires suggests, drop the center section.
On yours, if the axle code is correct, you have a limited slip rear. Be sure to use the correct oil.

 

Thanks guys.

Mike, I didn't know it'd take a certain kind of oil... What do I need?

 

Mobil 1 synthetic LS75W90 is a good one (note the LS prefix), you can use regular gear oil if you add a friction modifier to it. You should be able to get the additives at any auto parts store.
Just tell them you need oil for a limited slip rear, it should say on the bottle that it can be used in limied slip applications.
Just incase you don't know already H2J= (H2) Ford 9" 3.50 ratio limited slip 3750 lb capacity axle (J) w/ power steering

 

Thanks again Mike.