This might be a stupid question. I have experience with Lock-Rites and have seen LS diffs before. My question is my Axle code states I have 3.73 gears and a LS diff. Last year when I changed the fluid the case looked like a standard open diff. I spoke to a local shop and they said that the Ford LS doesn't look like a normal LS with the mechanism filling the carrier. He said unless you look closely you might not be able to tell it's a LS. I left it at that. It acts like a weak LS or a tight open diff. Today I had the rear off the ground and when I spin one rear wheel forward the other spins backwards. This tells me its open. Does this Ford LS have to have torque input to lock or do I have an open diff?

I just noticed this thread title sounds like it should be on a Neurology forum. No jokes plz.

 

You have an open. With LS if you spin one wheel the other should spin in the SAME direction. In open when you spin one wheel the other will spin in the opposite direction.

 

That's not what I wanted to hear. I was hoping they were spinning opposite because the pinion didn't have power to it.
Thanks.

 

What's your "AXLE" code from the door jamb sticker? In general, if it's a two digit number, it's open. If there is a letter and then a number, it's LS.

I'd think that even if the LS was worn out, the wheels should still turn the same direction when jacked up off the ground.

Mine is an H9 and both wheels spin the same direction when turned while off the ground.

 

Axle code is H8.

 

The following lists the gear ratios on rear axles.
19 - 3.55 non-limited slip (Econoline, F-150)
18 - 3.08 non-limited slip (F-150)
17 - 3.31 non-limited slip (Econoline)
H9 - 3.55 limited slip (F-150, F-250)
B6 - 3.73 limited slip (F-150, F-250)
24 - 3.73 (Econoline)
32 - 4.10 (Econoline)
35 - 4.09 (Econoline)
34 - 3.73 (Econoline)
39 - 3.55 (Econoline)
52 - 4.10 (Econoline)
56 - 4.10 (Econoline)
81 - 4.63 (Econoline)
27 - 3.31 non-limited slip (F-250)
26 - 3.73 non-limited slip (F-250)
41 - 3.27 non-limited slip (Explorer/Mountaineer)
45 - 3.55 non-limited slip (Explorer/Mountaineer)
46 - 3.73 non-limited slip (Explorer/Mountaineer)
42 - 4.10 non-limited slip (Explorer/Mountaineer)
D1 - 3.27 limited slip (Explorer/Mountaineer)
D4 - 3.73 limited slip (Explorer/Mountaineer)
D2 - 4.10 limited slip (Explorer/Mountaineer)
84 - 3.45 non-limited slip (Ranger)
86 - 3.73 non-limited slip (Ranger)
87 - 4.10 non-limited slip (Ranger)
89 - 4.56 non-limited slip (Ranger)
F6 - 3.73 limited slip (Ranger)
F7 - 4.10 limited slip (Ranger)
92 - 3.08 non-limited slip (Ranger)
R5 - 3.55 limited slip (Ranger)
91 - 3.27 non-limited slip (Ranger)
96 - 3.73 non-limited slip (Ranger)
R6 - 3.73 limited slip (Ranger)

 

I better actually check the door post then. I got that from Ford after giving them my VIN. My truck wasn't handy at the time. Thx.

 

Got it. Code on door is H6. This is a 97' Expedition. Service Dept at Ford says my VIN tells them 3.73 with LS. He says that with the LS it's possible for the rear tires to spin in opposite directions with the rear off the ground. This tells me that it needs torque input from the pinion to get them to lock. I didn't see any clutch pack in the carrier. It looked like a standard open diff (2 side gears and 2 spiders). Could I have missed the pack? I remember when I was looking at these trucks on the used car lots I was looking for the H6 code to make sure I got the 3.73/Ls.

 

Hello davet,

Go to your nearest dirt lot, come to a complete stop, then punch it, if you see two burn-out marks from the tires you have a LS, if only one, then open...

 

The 9.75 L/S carriers do not "look" like what you are used to seeing. They appear to be open. There are no metal "S" locks between the spider gears like you are probably looking for. The clutches and friction plates are between the outside case and the spider gears. If you remove the axles you can see them with a flashlight, or at least the top of them. The clutches do wear out like everything else does eventually. The rebuild kit is about a 100 bones with carrier bearings/races included. The better test would be to spin the driveshaft with the rear end off the ground, the primary drive wheel should spin no more than one turn before the other wheel starts to spin.

 

Thanks guys for the help. I spun the driveshaft and they both spin the same direction.