I have 2 f150 trucks
The first an 87
the 2nd a 94
With the rear end off the ground the 87 is stiff to spin the tires, the 94 spins very very easy.
Which is right, which is wrong, what do I need to check
Thanks
Sky

 

Both are right - you need to read your owner's manuals & What's the DIFF?.

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unfortunatly I dont have an owners manual, Just got the truck and it was not there. And the axle tag was not there as well, and somebody painted over the door sticker.
I would love some more info on why both are right.
Thanks
Sky

 

Different types of axles, most likely limited slip on one, and open on the other. There's normally a tag on the axle itself (on one of the rear diff cover bolts. What do those say? Steve's caption above explains the axle tag too. Follow his second pic.

 

Niether have axle tags, and the door tag on both are painted over. When I turn one wheel (on either truck) the opposite wheel rotates the opposite direction. Does that help any?

 

both are goin to spin the opposite way there both essentially the same in that they have spider gears inside the differential so that one wheel can if it needs to spin faster or slower than the other the only difference is the one with the ls has clutches in between the spider gears that the axle shafts slide into and have a metal s shaped spring in between the two spider gears to put pressure on the clutches

 

I think you have open(not limited slip) differentials on both vehicles. Try this test: Jack up just one rear wheel while leaving the other rear wheel on the ground. Shift your transmission to neutral so the driveshaft can turn free. Now try to turn the wheel that is raised off the ground. If you CAN'T turn that wheel you have limited slip. If you CAN turn that wheel, you have an open differential.

 

youll still be able to turn the wheel if it has limited slip itll just have more resistance might not have any at all if the clutches are smoked in it

which could explain why the tires spin opposite directions or he could just have open diffs best way to find out tear them diff covers off and take a look

 

Download the closest year you can get from Ford. It's free.Then click the link text in my previous post: "What's the DIFF?"

 

Even if the clutches were smoked, I think both tires would spin the same direction with a limited slip. I'll admit I could be wrong.

 

No, when the clutches wear out, it becomes an open diff. And the tires can never spin the same direction unless the trans/t-case is in N and both tires are off the ground. If the d'shaft is locked, then the tires must spin opposite, if at all.