TTORA Forum banner

1 - 10 of 10 Posts

Deal Master
2,773 Posts
Discussion Starter #1 (Edited)
Traction Aiding Devices - Locker , LSD , etc....

Copied & Pasted from previous discussions
-Thanks PinkTaco for saving the link because we all know Delphi's Search sucks

To lock or not to lock
By Murderman

..It was the best of times, it was the worst of times.....

There have been alot of good posts on this topic; here are some further details based on my experience:

There are five basic categories of differentials, that's right five! They are:

Open carrier
Limited slip
Automatic locker
Selectable locker

What these all have in common is that the torque is transmitted from the [input] pinion gear to the ring gear, which is bolted to the carrier. Through various methods, the carrier tranmits the torque to the axle shafts [output] through the side gears. Below is a description of how each works, and some sub-categories.

OPEN CARRIER - open carriers are found on most stock trucks and passenger vehicles. The reason they are called "open" is because the typical cast carrier is one-piece, and has openings in it to allow insertion and removal of the "guts". They are available in two, three, and four pinion [not to be confused with the drive pinion] designs; the more pinions, the stronger. Three and four pinion designs typically have a two-piece split carrier, because there would be more window than steel if a one-piece casting were used. If equipped with a open diff, the Taco uses a two pinion design. Bolted transverse to the axle axis inside of the carrier are the bevel cut[carrier] pinion gears which mesh with the side gears, which are splined to the axle shafts. Under normal straight line conditions, when the carrier spins, the pinion gears are static relative to the carrier, as are the side gears and both axle shafts spin at the same speed, and with the same torque as the carrier itself. When you go around a corner, the outside wheel [and axle shaft] must spin faster than the inside, because the tire travels farther along the larger radius. This "differentiation" is accomplished by one side gear transmitting its velocity to the other through the pinion gears. The side gear on the inside of the turn slows down relative to the carrier by exactly the same amount that the outside one speeds up. Since this operation is driven by the resistive torque of the tire on the road, when there is a substantial difference of traction available, such as one tire on ice or in the air, that tire will get all of the output torque. Believe it or not, most stock 4WD's are actually only truly 2WD.

LIMITED SLIPS - as the name implies, with LSD's the amount of torque differentiation between the two axle shafts is "limited", but not "eliminated". At best, they are about 60% efficient, which is why when one tire is in the air, it will spin relatively freely, and the other with the good traction will get essentially zero torque, just like an open diff. There are two basic types of LSD's, clutch type and gear type. Examples of the former are virtually unlimited such a Trac-Lok, Power-Lok, Eaton, Auburn, etc. The only two examples of the latter that come to mind are the Gleason Torsen and the TracTech TrueTrac. Clutch type LSD's are essentially the same as open diffs, except that friction clutches are included usually between the side gears and the carrier or between the side gears themselves to limit the amount of side gear rotation relative to the carrier. Because it is a clutch, there is always some slip, hence the 60% efficiency. Plate clutches are most common, but the Eaton uses cone clutches, and the Auburn uses coils springs and friction plates. Clutch type LSD's require a friction modifier be added to the axle oil to reduce chatter, and as the clutches wear out, the efficiency goes down. Gear type LSD's use a combination of spur gears and worm gears instaed of the typical bevel cut pinion and side gears. A combination of four sets of two spur gears and a single worm drive gear couple together are mounted transverse to the axle axis, and replace the pinion gear of an open diff. The spur gears mesh with each other to provide the coupling of one axle shaft to the other, while the worm drive gear meshes with the worm driven gears which replace the typical side gears of an open diff. Based upon the principle that on a worm gear system, the drive can turn the driven, but not the reverse, the theory says that the only differentiation which can take place within a gear type LSD is when one axle speeds up by exactly the same amount that the other slows down, as is desired when cornering on hard surfaces. In practice, however, some differentiation occurs under all conditions where there is a very large difference in traction available, such as when one tire is in the air. Gear types do not require special lubricants, and do not typically wear out like clutch types.

AUTOMATIC LOCKERS - My personal favorite - within the auto locker category, there are two sub categories; drop-in or "lunchbox" lockers such as LockRight, or full case such as TracTech Detroit [the original]. The operation of both is identical, but the full case design is substantially stronger. With a drop in, the stock side and pinion gears are replaced with a "cartridge"; the desirability of this type is that they are inexpensive, and installation does not require re-setup of the R&P. The basic principle behind auto lockers is that no axle can ever spin slower that the carrier, but either can spin faster. They sort of work like a ratchet wrench that works in both directions without flipping a switch; I know, it took me a real long time to get ahold of that concept too! This is accomplished by a dual castelated [?sp] profile on the mesh between the side "gears" and the carrier. When you go around a corner without applying significant torque, the outer axle shaft de-couples from the carriers and spins faster than it, while the inner axle spins the same speed as the carrier. Because the outer is de-coupled, the inner is carrying all of the torque; this is why lane changes can be a little wierd when the mechanism locks and un-locks. The upside is that they are very simple, provide superior traction under all conditions [even when one tire is in the air] and require no driver intervention; the downside is that they can make some noise when engaging/dis-engaging and they will stay locked whenever there is input torque applied. This is why they scuff the tires around corners in the rear or cause bigtime understeer in the front when turning [or trying to] with alot of power applied. Did I mention that Detroit's are my personal favorite?

FULL SPOOL - I desribe this one "out of order" because it relates to the selectable locker description below. There are two sub-categories of spools, "true" spools, and the notorious "Lincoln Locker", but functioning is the same. A spool replaces all of the various gears and the carrier with a single piece of steel [or sometimes aluminum for extreme drag race applications]. Basically, both axle shafts are directly coupled to the ring gear all of the time; there is absolutely zero differentiation under all conditions. Spools are pretty hard on tires when used on the street for a daily driver, and should never be used in the front if you ever want to make a turn. Traction is as good as it gets. "Lincoln Lockers" are created by welding the side gears of an open diff to the [carrier] pinion gears, hence the namesake reference to Lincoln welding machines. While this is a very cheap and easy way of making a spool, many people, myself included, generally consider it a bad idea because the open carrier is relatively weak to start with, and welding to hardened steel gears certainly does not help their strength. There are a few members on this board who have performed this modification without problems, but Tacos are not exactly high torque applications.

SELECTABLE LOCKERS - Selectable lockers are a combination of open diff and spool. The transition takes place based upon active manual input by the driver. There are three types; cable, air, and electric. Cable examples are the non-USA Toyota variations, the Ox-Locker, and I am sure there are others. The most common air variation is the ARB, and electrics are found in late model Taco's and Runner's. A new e-locker which has just been developed by TracTech is a combination of a spool and their TrueTrac LSD. Fundamental functioning is essentially identical for all types. A sliding sleeve is included inside the carrier, which locks one of the side gears to the carrier when engaged. Whenever on side gear is locked to the carrier, so is the other due to the coupling through the carrier pinion gears. This sliding sleeve is actuated by a shift fork very similar to those used in most transfer cases, connected to some form of drive mechanism, either a mechanical linkage [cable], a pneumatic diaphragm [air], or a solenoid [electric]. The upside is the versatility. The downside is the cost and complexibility. Due to the fact that they are all "fail-safe"; i.e., default to the open position, and distruption to the drive mechanism such as breaking a cable, ripping loose an air hose, or shorting out the electrics, will cause a lack of functionality. Depending on your perspective, the driver intervention could be either a good or bad thing.

Wow, that is a mouthful! My fingers are tired; I must really be bored today, or is it that I am just trying to avoid doing our income taxes?

Hopefully, y'all will find this informative; please let me know whatever errors I may have made.

Cheers, John

4,641 Posts
mudferret said:
He covered that under spools.
Ahh, I missed that part.

The smart way to weld carriers is to weld the spiders and the side gears, and cover the open part of the carrier with a plate that is welded on. People I know that have welded just the side gears have experienced the welds cracking and grenading the carrier.

Welding both sets of gears and adding the plates resolves the question of strength, regardless of the application.

Deal Master
2,773 Posts
Discussion Starter #6
Bump - Becuse lots of people are asking the same questions

180 Posts
Wow all the info i needed. Thanks!!!
1 - 10 of 10 Posts
About this Discussion
9 Replies
9 Participants
TTORA forum is the best Toyota off-road club around. We are nation wide with chapters in most states. Come in and discuss Tacoma, 4Runner, Highlander, & TRD models.
Full Forum Listing