When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Ok folks. Here’s my question. How can I tell if my differential has posi traction or not? The sticker in the door jam is long gone as well as any tag that could have been attached to the housing. 1989 F 150 two wheel drive. 8.8 rear. Thanks Jim
Jack up the rear end. With the trans in park (or in gear if manual trans), turn one rear wheel. If the other wheel turns the same direction, it's a posi. If it turns the opposite direction, then it is an open diff.
Jack up the rear end. With the trans in park (or in gear if manual trans), turn one rear wheel. If the other wheel turns the same direction, it's a posi. If it turns the opposite direction, then it is an open diff.
With the trans in park (or in gear with a manual) if you try to turn a limited slip you might not be able to. And if you are, the tires will turn opposite directions, just like an open diff. So with the trans in park (or in gear) you are looking for easy to turn is open, hard to turn is limited slip. But dragging brakes can make an open diff seem hard to turn, and a worn-out limited slip might be easy to turn, so this isn't 100% foolproof.
So leave the trans in neutral and do what jas88 said. That isn't 100% foolproof either, because if your ring gear and trans have very little drag it's POSSIBLE that an open diff will have both tires turn the same direction. But that's pretty unlikely (I've never seen it happen) so it's still a good test.
Chances are that truck has on open diff but if you want to know for sure pull the diff cover off and have a look. If it's never been off then the oil needs to be changed anyway, and if you find something that looks like this you have a factory Ford LS diff.
