What is a Limited Slip rear?

[flareside_thun]

It's relatively easy if you're not daunted. I'm looking for a link to a good write-up i ran across before but here's a video to tide you over... http://www.youtube.com/watch?v=0GsLDg3C6Hc

 

[LUCKYFORD]

what does a 95 250 auto di 4 wheel have out back. t will spin both tires.

 

[flareside_thun]

If it'll spin both, most likely a limited slip...the easy way to tell is look at the metal tag on the rearend. It should say something like 3 55 or 3L55 or 4 10 or 4L10. The L stands for limited slip.

 

[pybyr]

I've always wondered about those things. YOu're the first one I've ever heard with a first hand experience with one of the things. They always seemed like they would be a good option for a rig like mine where I tow heavy a lot. My LS works pretty darn well right now with fresh clutches in it but that I imagine will be short lived, even running synthetic gear lube. I was pretty impressed with the thing here last fall up around Leadville CO I was up running around on a bunch of 4x4 only roads without any trouble ( hey it's a dually, there were 4 wheels driving back there From what I'm gathering, with one of those Torsen jobs, I'd have the same type traction and maybe even a little better except it wouldn't wear out over time.
Those things drive me nuts though. I've looked and looked at them and can;t for the life of me figure out how on earth they could possibly function the way they say they do without consumable parts.

It was one of the AAM axles with the helical-gear torque proportioning differentia (same principles as the TrueTrac)l, and the proof was definitely in the pudding. One time I had that truck parked in a situation where one rear wheel was in a very wet grassy ditch and the other was on a gravel road, and it walked right out in 2wd without any spinning (it was a diesel, so lots of low end torque that could easily have spun things). Also made it all sorts of places in winter- without even having dedicated snow tires on it- without usually needing to be put in 4WD- places that I've usually needed to engage 4WD (even with snow tires) with other vehicles owned before and since. I was _really_ impressed and am looking forward to installing the TrueTrac in my F350. Supposedly the AAM helical differential has a lower maximum torque bias ratio than the TrueTrac, so the TrueTrac should work even better.

 

[MidnightBlade]

If it'll spin both, most likely a limited slip...the easy way to tell is look at the metal tag on the rearend. It should say something like 3 55 or 3L55 or 4 10 or 4L10. The L stands for limited slip.

some trucks don't have those tags from Ford, it is a royal painus in the **** trying to figure out watcha got

 

[Jbevs]

The axle code on the door jamb will tell what axle the truck came with, though it doesn't help if the axle has been swapped.

 

[MidnightBlade]

Never thought of that

 

[Jbevs]

Well, really it just gives you a letter or number or number and letter or something. You need the chart/book to actually tell you the gears. I think it's in the owners manual maybe.

 

[MidnightBlade]

We have a tech article on it I believe

 

[ocnorb]

Put a jack under the center of the diff and lift both tires off the ground. Spin one wheel. IF the other wheel spins the SAME direction you have some type of limited slip or locker. IF the other wheel spins the opposite direction of the tire you are rotating it is an open diff.

 

[MidnightBlade]

When I put my truck on jackstands one wheel spins forward and one spins backward. However when I get on the road and stomp on it both spin at the same time (proven by parrallel marks on the road ) SO IDK if my truck is just the difficult one or what but my dad's 99 Chev 2500 with a Posi will do the same thing mine does on jackstands

 

[flareside_thun]

Yea, if it's an open carrier one tire will spin, if it's an LS one will spin forward and one backwards.

 

[RLDSL]

When I put my truck on jackstands one wheel spins forward and one spins backward. However when I get on the road and stomp on it both spin at the same time (proven by parrallel marks on the road ) SO IDK if my truck is just the difficult one or what but my dad's 99 Chev 2500 with a Posi will do the same thing mine does on jackstands

If the tranny is parked in gear or in park ( slushbox) the LS will do the different direction bit but under resistance. Make sure to try the test with the tranny in neutral.

 

[ocnorb]

When I put my truck on jackstands one wheel spins forward and one spins backward. However when I get on the road and stomp on it both spin at the same time (proven by parrallel marks on the road ) SO IDK if my truck is just the difficult one or what but my dad's 99 Chev 2500 with a Posi will do the same thing mine does on jackstands

Yeah. A chev gov-lock will do that because it is essentially open until you put torque to it.

Another test is one wheel up in the air on a jack you don't care about- try to drive off of it with just the wheel on the ground (2wd). If you can you have some kind of limited slip, otherwise you'll be just spinning.

 

[MidnightBlade]

If the tranny is parked in gear or in park ( slushbox) the LS will do the different direction bit but under resistance. Make sure to try the test with the tranny in neutral.

I had the ZF5 in 2nd when I did it, never thought of that making a difference