Limited Slip Diff Always Slipping?

[GhostZero]

Hey fellow CTD folks-



I have an 06 long bed, quad cab, 4x4, manual transfer case, manual transmission. When I bought the truck I made sure it had a limited slip diff in it, although the extent of my verification was simply looking at the window sticker.



I tried an experiment yesterday- With the drivers rear wheel on ice, the passengers rear wheel on dry pavement, and the truck in 2wd, I hit the gas. The drivers side wheel spun but the passengers stood still.



Do I just not understand how a limited slip diff is supposed to work, or is it possible it's just busted? I would think that when the drive wheel started to spin that the other would kick in, and being on dry pavement it would have propelled the truck forward... After the little "test" I went and looked at my window sticker again- Low and behold, "Limited spin differential"...



Any thoughts?



Ghost.

 

[GhostZero]

And here is the answer:



https://www.turbodieselregister.com/forums/showpost.php?p=1632414&postcount=10



Thank you, HSpiering, for an awesome answer.

 

[GaryCarter]

Note the responding expert refers to "clutches" in the Dodge rear end. This is true for the earlier trucks but not true of the third gen with AAM axles.

The AAM is a gear operated -not clutch operated- torque biasing differential. Similar in design and operation to the Torsen.



IMO better for ice than the clutch type.



But any torque biasing unit has limitations in the torque bias designed in. In the scenario posted above zero times any bias is still zero. Meaning you need SOME resistance on the slipping tire to get traction on the other.



Gary

 

[RAlberg]

Note the responding expert refers to "clutches" in the Dodge rear end. This is true for the earlier trucks but not true of the third gen with AAM axles.

The AAM is a gear operated -not clutch operated- torque biasing differential. Similar in design and operation to the Torsen.



IMO better for ice than the clutch type.



But any torque biasing unit has limitations in the torque bias designed in. In the scenario posted above zero times any bias is still zero. Meaning you need SOME resistance on the slipping tire to get traction on the other.



Gary

This fascinating! Does that mean if the rear tire is spinning, throwing some sand or kitty litter on the road to get traction will result in both rear tires turning?

 

[TowPro]

It also means that if you put the emergency brake on a little both axles will think they have the same load and they both will turn. Heck, that even works in a "one wheeler" some.



Edit: Forgot the disclamer. Once get "un-stuck" remember to release the emergency brake

 

[Budpwr66]

TowPro, thanks for that pointer on the Emergency Brake... I never would have thought of that one.

 

[DonFitzwater]

Just a thought, I had an 04 that had limited slip on the sticker and after a trip back to the dealer, we found it never had one to start with? Who wooda thunk? They offered me the 295. 00 back or install the l/s..... went with the limited slip.

 

[J&LRam]

ghost

tow pros right. Look at page 198-200 in our owners manual and it states to apply the emergency brake slightly in the circumstances you had. I have been stuck with one wheel on snow pack and the other on wet pavement. I did a search and came up with a thread that had the same question and a answer from STAR " the transfere of power from wheel to wheel is torque sensitive and must have both wheels spinning [not stationary] to function. It is possible for the Trac rite diff to not send power to a wheel if its not spinning. Example: accelerating from a stop and one wheel is on ice and the other on dry pavement. If accelerating to fast , the wheel on ice may spin and never send power to the wheel on pavement side. A slower start may be necessary to start the vehicles momentum".

What a POS for a anti spin differential. We have 3-4 " of ice on the ground right now and the Dodge is in the tractor shed where it will stay till sleet/ice is gone off the roads. I drive my old '90 2500 5. 7 2wd with the factory G80 with 225k on it. The G80 will not let me get stuck as the Trac rite has. We have one hellova ice storm right now and more comming tomarrow. I had the tractor out which weighs about 8000 with frt loader and box blade. The tractor left no tracks at all on the ice/sleet. I wouldn't even try and move the Dodge. Maybe Dodge will give us a anti spin that works on ice.

JIM

 

[steved]

Note the responding expert refers to "clutches" in the Dodge rear end. This is true for the earlier trucks but not true of the third gen with AAM axles.

Umm, they do have clutches... they are called "drive shoes". These are not a true helical drive like a truetrac, close, but not completely.



The gears need load on both tires to load the drive shoes... in other words, the more load, the more traction...



steved