What is a Limited Slip rear?

[MidnightBlade]

Just curious what a Limited Slip rearend is and what other types there are.

 

[trapper]

the one wheel peel

 

[Roland_Jenkins]

I had a nice reply all typed out and then hit the wrong key and it all went PPPFFFFTTT

Anyways, Randy's has a list of different ones.

http://www.ringpinion.com/

I will say this, some work a lot better than others do.

 

[RLDSL]

A limited slip is just that, it allows one wheel to slip on pavement for turns , they usually have wet clutches with springs under really high tension keeping both wheels going together in mud, but in dirt or rocks they aren't all that stout and one can break loose and you can get stuck if in a tight spot A torsen gear drive limited slip doesn't have the clutches to wear out

Despite what folks say about the limited slips being worthless, , if they are fresh, they work pretty good. When I got my truck, the clutches were shot in the diff and I'd get stuck everywhere, but last year i rebuilt the thing and it grabs very nicely now.

next up is the Lockers either automatic or air powered and those critters will lock both wheels together preventing any wheel slip maximum traction , but possibility of breakage if you tow heavy

least desirable is open diff where there is no resistance between wheels, and you get stuck in a heartbeat

 

[gonecrazyi]

Limited slip is not one wheel peel.

There are clutches that allow power to be split between the axles. The condition of the clutches helps determine how much power isput to both wheels instead of just one. That's a pretty basic definition. I've never taken one apart so I really can't say to much more.

I will say that I get stuck a lot less in 2wd with the ls rear than with an open one.

 

[gatorman21218]

from what I understand is this.

On a rear axle the wheels are fixed, therefore on a right hand turn, the left wheel is going to spin faster than the right.

Now on an open diff, the wheel is allowed to spin and the power is only applied to the inside wheel of the turn. Also If you are in mud, only one wheel will spin. Anybody remember My Cousin Vinny?

On a limited slip diff, there are clutches to allow the outside wheel to turn around a corner, but if you are in mud or someones lawn, the clutches prevent the wheel from spinning and applies power to both wheels.

A locked diff is just that. both wheels are locked. This is why cars/trucks with locked diffs will chirp the wheels in parking lots and such

 

[GOOSE]

An open rear uses spider gears as stated and offers the most friendly street manners. These are the one wheel wonders and will keep your from going sideways when you spin a tire, the non spinning one continues to keep the vehicle on track. If one tire is on ice and the other on dry pavement , the one on ice will spin and you will go nowhere. Put your truck on jackstands. If you spin one tire and the other goes in the opposite direction, you have this.

Next is limited slip. Here there are a clutch pack being held together by high pressure springs as mentioned. Both tires will receive torque from the engine with this setup. Go back to the scene with one tire on ice and the other on dry pavement. Now the tire on pavement will receive power from the engine through the clutches. These clutches are what connects your left axle to the right one. Over time these springs and clutches tend to wear out and a limited slip axle will behave more like an open rear. On jackstands, both tires will spin in the same direction.

Next up the ladder is a locking differential. Instead of clutches, there are cogs that connnect the axles together. In the ice / pavement scenario, both axles will receive full torque and spin. If one tire is in the air and the other on a rock, both will rotate as they are connected through the cogs. When you let off the throttle to go around a curve, the cogs release allowing the tire to spin at different rates of speed avoiding chirping. Hit the gas in mid curve, the tires lock, usually dragging the inner one or spinning out your ride if you have the power. It is really easy to spin out a truck in the rain with one of these. I personally ran a 74 390 4bbl f100 for about 85,000 miles with a Detroit Locker and was very pleased with it.

There are various kind of lockers. A Detroit Locker is always there and usually bulletproof. Different selectable lockers use 12 volts or air pressure to engage or release. These offer the best of both worlds and can be used in the front or rear of a truck. They are a locker when engaged and an open rear when turned off and pretty expensive.

At the top of the ladder is a spool. These permanantly lock the axles together and are usually on 1/4 mile cars or off road only vehicles. These are not very friendly on the street, both tires will turn at the same rate and chirp when turning.

 

[MidnightBlade]

So, this winter I tried to climb a snow pile in 2WD, got stuck with the fornt end on the snow pile and the rear on soggy grass, I now have 2 6" deep ruts to fill in, side by side. That throws out the Open Diff and leaves either the LS or Locking Diff. (another name for a posi.??)

 

[gatorman21218]

http://www.drivingfast.net/technology/differentials.htm

heres a little article that helped me understand.

And Posi-traction is Chevy's brand name for limited slip. heres a list of all the brand names.

* Alfa Romeo: Q2
* American Motors: Twin-Grip
* Buick: Positive Traction
* Chevrolet/GMC trucks (after 1973): Gov-Lock
* Chrysler: Sure Grip
* Dana Corporation:Trak-Lok or Powr-Lok
* Ferrari: E-Diff
* Fiat: Viscodrive
* Ford: Equa-Lock and Traction-Lok
* International: Trak-Lok or Powr-Lok
* Jeep: Trac-Lok (clutch-type mechanical), Tru-Lok (gear-type mechanical), and Vari-Lok (gerotor pump)
* Oldsmobile: Anti-Spin
* Pontiac: Safe-T-Track
* Porsche: PSD (electro-hydraulic mechanical)
* Saab: Saab XWD eLSD
* Studebaker-Packard Corporation: Twin Traction
* TVR: Hydratrak

 

[RLDSL]

So, this winter I tried to climb a snow pile in 2WD, got stuck with the fornt end on the snow pile and the rear on soggy grass, I now have 2 6" deep ruts to fill in, side by side. That throws out the Open Diff and leaves either the LS or Locking Diff. (another name for a posi.??)

It's kind of funny, 4x4 will fake people out. With open diffs, if one wheel slps you are dead in the water. You can go places with a 2 wheel drive with a locker that a 4x4 with open diffs can't even dream of. I've got a couple of Volvo cars that came with Dana30 rear ends with an Eaton locker from the factory and I regularly get 4x4 owners mad as heck at me in the winter when I go tooling on by them in the ditch waiting on a wrecker. Really ticked off a guy I went to buy a boat from a few years ago when his 4x4 cheby with mud tires couldn't pull the boat and trailer up a muddy ,grassy hill and I hooked up to it with summer tires on a rear wheel drive passenger car and walked right up it

 

[pybyr]

There's also the Torsen-type torque proportioning helical gear diffs, which, to my mind, are pretty close to best of both worlds for the widest range of situations (had one in a Dodge a few years ago and it was great). They act like an open differential in terms of driveability, but if you're in limited traction conditions, they send more power to the wheel with better traction, up to a ratio of about 3:1. I have a Detroit TrueTrac of this type that's going to go in my truck this coming summer.

 

[rjjp]

It's kind of funny, 4x4 will fake people out. With open diffs, if one wheel slps you are dead in the water. You can go places with a 2 wheel drive with a locker that a 4x4 with open diffs can't even dream of.

Very true, my 2wd diesel has gone places that my old 1990 F150 4x4 couldn't, mostly dragging it on the end of a chain to get it out. But tires make a huge difference to, my dad has an 05 F250 4x4 with BFG trailmasters, I walk through places with 2wd then have to go back and pull his ass out.

 

[RLDSL]

There's also the Torsen-type torque proportioning helical gear diffs, which, to my mind, are pretty close to best of both worlds for the widest range of situations (had one in a Dodge a few years ago and it was great). They act like an open differential in terms of driveability, but if you're in limited traction conditions, they send more power to the wheel with better traction, up to a ratio of about 3:1. I have a Detroit TrueTrac of this type that's going to go in my truck this coming summer.

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.

 

[hesutton]

There's also the Torsen-type torque proportioning helical gear diffs, which, to my mind, are pretty close to best of both worlds for the widest range of situations (had one in a Dodge a few years ago and it was great). They act like an open differential in terms of driveability, but if you're in limited traction conditions, they send more power to the wheel with better traction, up to a ratio of about 3:1. I have a Detroit TrueTrac of this type that's going to go in my truck this coming summer.

I've had a Detrioit True Trac gear driven LS in my rear axle for close to 5 years now. It has worked better for me than traditional clutch or cone LS's I've used in the past. The inproved bias ratio seems to be part of the reason. The other thing I like is there are no cltuches, springs, cones to wear out and NO SPECIAL FRICTION MODIFIER in the gear oil. Just fill the diff with regualr gear oil and go.

Heath

 

[gatorman21218]

how hard is it to a) refresh the clutch packs in my factory LS or b) add one of them lockers

I havent gotten stuck yet (knock on wood) but with 280000 miles on the rear I can imagine those clutches are not factory fresh.