So, we all know the Open vs Limited Slip vs Locker vs Spool debate, but I was wondering what's the best type of Limited Slip differential? I've done a fair bit of research and found this:

Open Differentials are cheap and easy. By applying more torque to the tire with less resistance, it lets the outside tire in a turn rotate faster than the inside tire making turning smoother. The downside to this effect is that if one of the tires starts to lose traction, it makes it much easier for it to lose traction completely, the other tire will be "seen" as the tire with more resistance, and the tire with less traction will get more of the power, until the point it has no traction and has all of the power. It's not good from a performance standpoint, because if you ever lose traction, you lose a large chunk of power until you regain traction, and it can lead to extremely dangerous situations in snow/ice/rain situations.

Spool and mini-spool differentials do exactly the same thing, full spool is just stronger than mini-spool, and harder to set up. Full spool completely replaces the carrier and the ring gear bolts to it, while a mini-spool replaces the spider gears inside the carrier. Spooling locks both wheels together, so they always rotate at the same speed. No matter what. Great for straight lines, horrible for turning. I believe they are able to snap an axle if they have to turn at high speeds.

Lockers function as a spool, and as an open differential. There are two types, one being automatic, the other being selectable. The automatic locker will switch between an open and spooled type differential with no action on the driver's part. They will only function as an open during cornering, where one tire HAS to move at a faster pace than the other tire, and the rest of the time will function as a spooled differential. Unlike an open differential though, neither tire can move slower than the differential carrier, but one can move faster. The automatic locking differential also can make turning difficult, seeing as it can lock and unlock several times during a turn. It can also accelerate tire wear. Manual lockers function similar to automatic, but are generally left in open configuration, and only run in locking configuration when needed (race time). Both of these styles can apply 100% of your engines torque to the one axle that has traction, so lockers have the ability to break axles.

Now, with limited slip differentials, there are a lot more choices. There are two main categories, and they continue to break down from there. The two main categories are the torque-sensitive and the speed-sensitive. The two types of torque-sensitive LSD's are clutch-type and gear-type, and the three main types of speed-sensitive LSD's are viscous fluid, gerotor pump, and electrionically controlled.

The clutch-type LSD is operated by driveshaft torque. The more torque applied to the clutch-pack, the more locked the differential is. These are also the 1 Way, 1.5 Way, and 2 Way differentials. The 1 way version will stay in a locking state until the gas pedal is released (on acceleration only), which makes it easy to turn by just lifting up off of the gas. The 2 way stays locked even when the car isn't under acceleration (acceleration and deceleration), which makes turning a lot harder, but you can alternate between the brake and the gas without the feel of your turning changing, making it easier to heel-toe the gas and the brake to get optimum turning while racing. Not quite as useful on the street, where if you need to brake in an emergency, you'll likely need to quickly swerve as well. A 1.5 way operates in between these two states on deceleration, and will be "partially" locked while decelerating (full on acceleration, half on deceleration). This is a compromise between safety and performance. Downsides are: Clutch-wear, price, and noise. They require more maintenance than any of the other kinds of differentials, and can suffer from lack of maintenance.

Gear-type use worm gears to engage both of the wheels when the torque in between the axles differs. They use a worm gear and worm wheel setup that is extremely difficult to explain, but they use an extraordinary worm gear setup that will speed up the outside wheel by exactly how much the inside wheel is slowed down by. For a better example, look at the end of the page here. The major downside to gear-type LSD differentials is that if they lose traction completely on one wheel, it behaves exactly like an open differential. They are usually cheaper than clutch-type, wear much less, and are less sensitive to lack of maintenance.

Speed-sensitive differentials work based on the difference in speed between the two axles. Viscous fluid-type LSD's have a canister of fluid inside the differential with one end hooked to one axle, and the other end hooked to the other. When the speed between the two differs, it shears the fluid on the inside, which gets thicker, making it harder to shear, and transferring power between the axles. Downfalls of the viscous LSD are that with wear the fluid eventually wears out, but at least it fails well, it turns into an open differential. There is no way to service the viscous fluid, the whole canister (and I believe differential) must be replaced. If traction is lost on one wheel the opposite wheel will still get power, but not as much as the torque-sensitive LSD's. A downside to this is the amount of energy lost by the fluid, in a similar way to the energy lost by a torque converter.

Gerotor pump differentials work on a similar principle, except it creates a pump using an axle and the differential carrier, and using the pump it compresses a clutch pack as the speed between the two wheels differs. Most new ones also implement some kind of computer control.

Electronic differentials aren't really differentials at all. They are an open differential that uses ABS to slow the wheel that has no traction, effectively giving the other wheel (which in a normal open diff would have no traction) traction.

But my big question here is which is better? Spool is mostly a race-only decision, lockers are for more strip/street than street/strip cars, open differentials aren't good from a performance standpoint and can create dangerous situations in a daily driver, so it looks like LSD is good for the street/strip car.

But then which LSD? Viscous loses power due to the nature of fluid transfers, gerotor has a similar issue but actually locks with a clutch. The best of the speed-sensitive seems to be the Electronic, but that requires ABS, which needs different sensors, brakes, a computer, etc. So without doing a full ABS conversion that really leaves the the torque-sensitive diffs. Clutch-type are good because they will never behave like an open differential, but they wear and require a very specific break in period. They are also generally more costly. Gear-type are difficult to break, don't require much in the way of maintenance, and as long as both tires have some traction, operate well. But the downside is the exact same as with an open differential, if one tire loses all traction (Ice, hydroplaning, etc) they give all of the power to the wheel with no traction.

Which would you choose, and why?

Notice: All of the information above is the reflection of my searching, and may be just as wrong as where I found the information. A good portion of my knowledge came from HowStuffWorks, Wikipedia, and reading around different manufacturer websites and forums. Any and all of the information above could be wrong, and if you see something that is, feel free to correct me. Maybe this could be a helpful thread for anyone wondering what to do. Thank you for reading.

 

I went with the Detriot TruTrac, gear type LSD for my Dana. The clutches were burnt out on the 9 bolt I replaced.. seemed like the best option to me. The Trac Loc ( i think it's called ) standard LSD Dana differential needed some fixing... little spring clips on the clutch packs were broken. So 2 clutch type differentials that needed fixing... I figured I didn't want to deal with that. Plus I read a lot of positive things about the TruTrac

 

i vote for sticky

 

That's a damn good post there, lots of good info.
They say a spool can break axles, I don't think that's because it's turning too fast (i'm imaging you using it on an autobahn sorta thing, just driving it fast wouldn't break the axle). I think it's because the spool is strong, that leaves the next weak link - axles. Assuming you don't wipe the teeth off the pinion first...

That being said, i'm going to go for the Detroit true-trac as well. No maintenance and high strength are a plus for me, along with the lower cost. Just to throw out an example, the Torsion from the 4th gen cars is a type of helical gear posi like the tru-trac.

I have heard about the 0 traction to one wheel makes it like an open as well. I think what I read was talking about when driving on ice or if one tire hits a puddle and hydroplanes. **Edit, just realized you wrote exactly that in your last paragraph*.

 

I dunno. The geared LSD's seem great, but I do lose traction a lot in the rain. More things to think about before the big S60.

 

Awesome Info!! I also vote for a sticky!!

I had a full spool in the Camaro I currently own. I bought it that way. I hated that full spool, and it was no fun having both wheels turn at the same speed on teh street, let me tell ya....... I went with a Moser 12 bolt and a Detroit True Trac...

Lastly third gens are cool!! I have owned 4 Camaro's in my life, 2 were third gen's!! I'm looking for either a 1989 or 1990 IROC with a 5.7L and the 8th digit of Vin code 8. No 305's!!

 

sticky please lots of awsome info for us younger guys

 

Because this is a good thread, I'm gonna bump it.

 

LSD Helical gear type, like the Detroit Truetrac and the Quaife Hydratrak, and the Torson are the best for the street bar none. They by mechanical design distribute torque to whichever wheel turns faster. This is the exact opposite of what an open rear end does. In an open rear end you can lift one driving wheel off the ground and put a running car in gear and it will go nowhere because the mechanical design gives all the torque to the faster turning wheel. With a Helical gear type limited slip diff, like the truetrac the mechanical design gives the torque to the slower wheel. In the one wheel off the ground case it would go to the wheel on the ground. Result is when you have traction on both wheels they get equal torque like a spool or locker. When you don't the wheel with the most traction gets the most torque. Simple fool proof and great and no drawbacks. Ideal for the street.

Spool. Now for a strip only car a spool might be best. It simply locks both wheels together so they both turn the same speed all the time. It does not like to turn corners and would soon break and or eat the rear tires on a street car.

Locker, A locker is a diff that by one means or another Locks and acts like a spool sometimes and unlocks and is like an open rear other times. They do make a decent street or strip rear. However the unlocking/locking may not occur when you want it to/ can be noisy and jerk you around. IMO they suck except when drag racing or offroading, not as much as an open rear, more than any LSD.

POSI is just a name for an old type of Borg Warner made Limited slip diff that used friction clutches. Better than open but they only transfer some torque under some conditions and they wear out and they suck.

LSD Limited slip differential most non helical gear diffs use some sort of friction device cones or discs or what have you to transfer some torque to the Other wheel. They are basically open rears that have a torque transfer device in them to partially drive the slower turning wheel. They are better than a open rear but they wear out and they slip more and they suck.

Good news is if you have a 10 bolt rear you can get a Detroit TrueTrac that will fit it for a reasonable amount of money IE less than $500 bucks around $350 -400 really.

If you have any non stock rear in there like a Dana or a 12 bolt or a Ford nine inch you can get a Detroit Truetrac to fit it reasonable IE less than $500 bucks.

Now for the bad news. If you have the GM nine bolt Borg Warner BTR 78 7.75 inch ring gear that came in the IROC and GTA you are SOL amigo. No one in the world not Australia, or Japan or England or New Zealand or Canada or anywhere makes a Helical gear LSD for that @$#@#$ rear end which I myself have. You can get the Borg Warner made stock cone type maybe somewhere, or an expensive German made clutch disc type ( More than a currie 9 inch with a truetrac expensive I kid you not.) LSD for it and a Aussie Ford bit that might work for like $800 bucks US other than that no joy. I'm gonna toss mine and get a Ford 9 inch for it. Moser and Strange among others have other options for you. You could salvage a 10 inch from a lesser vehicle and get a Truetrac for it, and save some cash, a good choice would be a 4 th gen V8 10 bolt with the good discs on it.

Lastly some specs on the GM 9 bolt.

http://www.accuautoparts.com/axledes...xleid=G775REAR

Hope this helps some of yall.

 

When you hit the puddle scenario just put the brake on a little it will cause the Helical gear LSD to torque transfer to the wheel with traction. Offroader trick.

 

Agreed, lots of good research/info here.

As for my personal opinion ...
I picked up a 3.23-disc-posi, and started renovation.
When I got to the carrier (Auborn, clutch cones), the
cones were split, and fell off. Auborn advertises this
configuration as replacable, not servicable. For me, the Eaton
clutch disc configuration seemed to be the desirable
alternative, with respect to configurability (options of
springs/clutches can be configured from mild to extreme,
and are individually available) and cost, for a street-strip
application. I think the Detroit Locker web-site indicated
those units more for off-road.

Anyway, thats my story, & I'm sticking with it.

 

mmadden55, I've got a few problems with your post. First, Posi is a trade mark name for the Eaton brand limited slip differetnial, not Borg Warner. Posi and Positive Traction were the names used for the Eaton that was installed in the old Chevy 12 bolt car rear ends. The name posi caught on and people started using that name for all limited slip differentials. The Eaton Posi is a clutch type LSD and in my opinion it is the very best street/strip differential for GM rear ends.

The Truetrac and Torsen have some problems. They don't always lock up when doing a burnout or when drag racing. MANY times they will allow one wheel to spin without the other. They are better in a road racing car and for auto cross. Im my opinion they are not the best street differential, but they do run close behind the Eaton. The Eaton can be rebuilt and it can be tuned to fit your needs. There are 3 different clutch designs and 3 different preload spring sets available that allow you to tune it for the amount of lock up that you want.

 

The Truetrac Torsen and Qauife are all better than any clutch or cone type LSD in that any of them can and do transfer up to 100% of torque to whichever wheel has traction. The clutch type LSD you refer to when in perfect operating condition still transfers less than 40 % torque and they wear out quickly. The Helical gear LSDs like the Truetrac always transfer torque to the slowest turning wheel if they have any resistance to work with. In short the only time you will get one wheel spin is when you are at a dead stop and have no traction at all. And then you can simply touch the brakes to provide a little resistance to transfer torque. This does not apply in a drag race situation. In fact there is a guy on another forum I frequent who launches is 1200 hp TT Viper with a Qauife Helical gear LSD. So no. The Borg Warner unit was also called a Posi as is the Eaton unit which they still sell under that name btw both are clutch type LSD and better than an open rear but nowhere near as good as a helical gear LSD like the Truetrac.

 

Would someone like to implement drifting into which type is best to do so with. Im subscribing to this.

 

With drifting you want steering effort to remain constant whether you're braking or accelerating, so you'd want a 2-way clutch type.

mmadden, in your one wheel off the ground scenario the worm-gear diff and the open diff will behave the same.

 

Please when this becomes a sticky? post for each type of racing whether street, drag, auto-x or street. So anyone can come here and check out some good recommendations for their applications needs. Thanks.

 

Strip: Spool
Strip/Street: Locker
Street/Strip: Gear-type
Street: Gear-type or Clutch-type, driver preference
Auto-X: Clutch, #-way depending on preference
Drift: 2-Way Clutch

Speed-sensitive diffs are generally designed for certain applications rather than easily retrofittable, which is why I didn't recommend them.

 

Well mmadden, I still disagree with you about the gear type differential, but I'm going to drop it. As for the Borg Warner differential, it can not be called a Posi because that is a registered trade mark of Eaton and it would have been illegal for B-W to use that name.

My opinion is like this.
Drag racing spool
Strip/street Detroit Locker
Street/strip Eaton Posi
Auto cross or road race Truetrac
Dirt track mini spool
Drifting I would use a locker of some kind. I don't think any of the limtied slip differentials (clutch or gear type) would be good for that. A spool might even work in that situation because you want to keep both tires spinning at ALL times. The ARB or E Locker might be a good choice.

 

Positraction was originally a trademarked name, but is now what any form of LSD is called. Or are you the person who calls your Equate brand Band-Aids Equate Brand Self-Adhesive Medicated Strips? This board needs an eye-rolling smiley face.

Why would you recommend a mini spool over a full spool? Full spools are stronger and behave exactly the same.

 

A full spool requires c clip eliminators, which aren't always needed. A mini spool can be used with c clips. Most stock body dirt track cars can use c clips on the axles and keep the axles in the car easier, especially the left axle.

I don't call my Stihl trimer a Wead Eater, I don't call Advil Asprin and I don't call inline skates Roller Blades. An Eaton is a Posi, a Spicer LSD is a Power Lock, an Auburn is a Sure Grip if it's in a Mopar. I don't use Equate, I use Band-Aids. Yea, I'm **** and it drives my wife crazy.

 

I call Advil ibuprofen, Tylenol acetaminophen, that way if people have an alternative I can still get what I want. :P

 

Found this, may help out some as well. A different POV?
http://www.houseofthud.com/differentials.htm