1984 F150 differential?

Changing the oil in the rear differential on an 84 F150. 2 wheel drive, 4 speed. No badge or marking on the differential that I can see indicate whether it is limited slip or not. Manual and Haynes don't indicate either. Any ideas as to which it is?

Thanks.

If you can, jack both rear wheels off the ground. Turn one of the wheels, if the opposite wheel turns the same direction it is limited slip. If the opposite wheel turns the opposite direction, it is not limited slip.

Another way, jack up just one rear wheel and put the transmission in neutral, if you can turn that one wheel and it turns the driveshaft, you don't have limited slip.

Great. Thanks a lot for the info. Been trying to figure out what it was for two or three months. Called the ford dealer with the VIN number and been scanning the internet but couldn't find anything.

I don't have a limited slip differential- but out of curiosity, what is the purpose or the mechanics behind the wheels spinning opposite directions when they are both without load?

I don't know. I guess it just works out that way with the spider gears and all. That's the best answer I can give you.