Topic: Auto Locker Functionality Explained by John Zentmyer (Lock-Right inventor)

[blackdiamond]

BACKGROUND
After a lengthy discussion recently on the forum related to the function of automatic locking differentials, I contacted Torq-Masters to see if they could confirm for me that torque is not a factor in the functionality of an automatic locker. I had contacted Torq-Masters in years past and found them to be both helpful and friendly. This time I was really impressed when I was put into contact with John Zentmyer, the engineer who invented the Lock-Right and is currently consulting with Torq-Masters. He designed the new TorqLocker initially for the Spicer (Dana) 60, and there are more in the pipe. This design eliminates the pins found in other automatic locking differentials by using a keyway slide-in design. With permission, I am passing along the core of our conversation as it related to the functionality of automatic lockers.

https://www.torqmasters.com/torq_locker_dana_60_35_spline_tl_16035_tor

If you have any questions for John I would be happy to pass them along and post his response.

EMAIL 1 (to Torque-Masters)
Any chance the new key-way design of the 1-ton plus lockers will make its way into the regular lineup? On the surface it seems like a far superior design unless there are space/configuration constraints that prevent it from being an option.

Also, I have recently learned (assuming that it's correct) that torque has nothing do with an automatic locker unlocking or re-locking and it's just related to the relative speed of each axle. I have a Detroit locker in the rear of my 89 4Runner and an Aussie Locker in the front. In your Aussie Locker Operator's Guide backlash is described as the cause of the "clink" or "clunk" sound that is heard. I've always envisioned the side gears getting compressed without actually meshing the teeth and then the noise is heard when the teeth snap together. With my Detroit Locker it will sometimes sound like an axle broke. Can you explain specifically which parts and what is happening to make the noise?

RESPONSE 1 (from Torq-Masters)
The new TORQ Locker will eventually be available for some of the OE axle differentials. We now have the TL available for the Spicer (Dana) 60 and the GM 14-bolt (split case). The only Toyota axle we are considering for now is the Toyota 8”. We also have other OE axles in development and a couple are close to prototyping. Stay tuned!

We would love to help with your questions. I've copied in John Zentmyer, one of the more seasoned experts in the field, who is the inventor of the Lock-Right Automatic Locker and of our TORQ Locker.
RESPONSE 1 (from John Zentmyer)
Good questions, and yes, you got it right. In mechanical terms, the automatic locking differential is a speed-activated “bi-directional over-running dog clutch.”  That is to say that when one side wants to go faster than the other side, it disconnects and speeds up (over-runs) until it doesn’t want to over-run any more, whereupon it re-locks and goes at the same rate as the first side. The term “dog” in this context means “tooth”, and clutch, of course, implies a disconnecting mechanism of some sort. Being bi-directional, it works equally well in both directions. This speeding up and slowing down are due to the different turning radii of the wheels on the ground during turns--the outside wheel will turn faster than the inside wheel and will resume the same rotational speed when the vehicle straightens out. Thus, you are correct that torque has nothing to do with it-—it’s all relative speed.

The Aussie Locker (and the others as well) needs about five degrees of backlash at the locker to disengage. That amount is translated upward by the gear ratio, so that, for example, with a 4:1 gear ratio the drive shaft would see about 5 x 4, or 20 degrees. This isn’t huge, but it does create a “clunk” going from drive to coast. It won’t always be 20 degrees because it depends on the relative position of the teeth for each axle gear, but for easy explanation, that’s about it.
         
The other noise you mention is what we call “click” rather than “clunk”, and that is what you’re describing when the teeth of the cam gear connected to the faster wheel go in and out of its associated axle gear teeth during a turn. The speed of the click depends on the tightness of the turn, and as the vehicle straightens out the clicks become slower and then stop when the vehicle is going straight again.
         
The Detroit Locker was invented in 1939 by Roy Thornton of the Thornton Tandem Company. They made 4-rear-wheel drive bogie assemblies for large trucks. Back then it was called the "No-Spin" and it was first put into International Harvester 2-1/2-ton 6x6 trucks during WWII. They were extremely harsh because the teeth kept going in and out during a turn and the halves were forced inward for engaging by huge coil springs (they still are). The No-Spins really made a lot of noise and had harsh operation. They were not at all suited to smaller vehicles. Sometime in the late ‘50s or early ‘60s they were being made by Detroit Automotive and they wanted to broaden their line, so they added what they called a “holdout ring” and called it the “Detroit Locker.”  This ring kept the teeth of the faster wheel’s outer clutch member (connected to the axle) from engaging during a turn, but as this wheel slows down and reaches the speed of the other one, the holdout ring is supposed to get out of the way and allow the teeth to re-engage. Sometimes it gets out of the way at the wrong time, so you get the famous “D.L. bang” as the vehicle is coming out of a turn. Thornton’s original design with the added holdout ring is still being made today, so it’s had quite a long product life.
         
The first serious potential competition to the Detroit Locker was the All-Trac, which I invented during the 1983 -1985 time frame. It was made strictly for the Dodge Power Wagon and its military cousins (WWII 3/4-ton 4x4 and 1-1/2-ton 6x6, the M37 and M601 Power Wagon and numerous variants). Detroit Locker didn’t have a product for that niche market in the early ‘80s, although they did have one briefly in the ‘60s (model KS-22A), so no problem at that point with any competition from me. However, in 1989 I adapted the All-Trac design to a Toyota 8" differential and called it the L.A. Locker. Problem. I had to change the name to Lock-Right, and it so remains today. Due to too long a story, I am not involved with the L-R anymore but have been quite involved with the Aussie people as a consultant for a number of years. I developed the 1-ton TorqLocker you asked about as well as several other models that are being readied for the marketplace, with patents pending. The Aussie people are first-rate and have a great company for taking the TorqLocker into the future as well as for maintaining the existing design in the marketplace. As you know, the Aussie product is 100% made in the U.S.A. If you want a Chinese locker or one made in India, you can buy something else.
         
In a nutshell, that’s about it. If we can be of any more assistance, please don’t hesitate to let us know.

[blackdiamond [OP]]

EMAIL 2
When I built my 1989 4Runner (1985 front axle swap) in 2002 I chose a Detroit Locker for the rear and an Aussie Locker for the front.  Around that time I was able to hold a Lock-Right in my hands and was impressed by the stiffness of the springs. When my Aussie Locker arrived I was equally surprised at how soft the springs were in comparison.  Is there any correlation between the spring rate and how easily the locker can unlock?

Clearly, selectable lockers provide a lot of flexibility, especially on the street, but in my experience almost everyone that runs them ends up with a reliability issue sooner or later. I chose automatic lockers because I want both strong and reliable products.

I have never run a "lunchbox" style locker in the rear but would expect to hear a lot more ratcheting noise than with my Detroit Locker that I really don't hear at all other than the big bangs from time to time.

I love the value of the Aussie Locker in the front and they definitely seem to be strong enough for my application.  When I was making my selection it seemed that the Aussie Locker was stronger (i.e. less reported broken) on the forums compared to the Lock-Right. Clearly you're in a position to know the pros and cons of both. Any comment?

I read an article last night (and old one that referenced you) that indicated that the Lock-Right allowed the inner axle to go slower rather than the more common explanation that the outer axle is allowed to go faster. Did they describe it incorrectly or in a confusing way or does the Lock-Right really work the opposite way of the Aussie Locker?
      
RESPONSE 2 (from John Zentmyer)
Answering your questions in order:
   
1. Stiffness of the springs. This design of automatic locker will work with a wide range of spring pressures. Part of the design choice is the size of the locker(s). If a particular spring is going into a large locker, it should be stiffer than those going into a smaller locker because of the larger mass (cam gear) the springs have to move. To have one spring be used across a broad line requires that a stiffer spring go into the smaller lockers. That being said, a lighter spring will work with larger lockers until it gets too light. The choice depends on several factors, only one of which is the mass of the cam gear. The Spartan has fairly stiff springs operating inside small holes, but I haven’t had any personal experience with them so I’m not familiar with the harshness that’s been reported.
   
2. Selectable lockers. While it’s true that selectable lockers offer flexibility, they also offer a spool off road. While that might not seem to be too bad, it does tend to produce understeer on hard dirt and can put significant torsional strain on the axle shafts when turning on rock. Also, until there’s no torsion both axle shafts, even for a brief instant, they won’t release (nor will manual hubs). I view the Aussie-style locker as being the best of both worlds, tending toward the larger vehicles because the longer the wheelbase and the heavier the vehicle the less you’ll notice a locker in the rear. As I was developing the Lock-Right I had a Lincoln MKVII that had a Ford 8.8 limited slip in the ass end. I machined a couple of special adapters to replace the clutch packs and ran the Lock-Right on the street (obviously) for about three years until I sold the car, when I put the limited slip back in. I never really went off-roading with it, but I do have the distinction of driving it right up to the base of the hill at Lion’s Back in Moab. It looked like I would have ground clearance problems, so I didn’t try climbing it. (Not to mention steepness problems?) I still have the adapters and probably the locker too. I should have taken a picture there, but I don’t think I did.
   
3. Detroit Locker noises. The holdout ring prevents any engagement of the teeth while the vehicle is turning, so you won’t hear any ratcheting at all other than, as you point out, when it sometimes does its famous bang upon re-engaging. I realize that I can’t be totally objective, but that being said, especially for larger vehicles, I don’t think that an Aussie is all that objectionable in the rear. The L-R sure wasn’t in the Lincoln, which I used for demos for potential customers. I couldn’t hear it at all, and the only time I noticed it was getting on and off the gas in a turn, which tends to very slightly swerve the front end from side to side because power is being applied to the ground by the inside tire during acceleration and by the outside tire during deceleration (see below). Never had an issue with it, though, and it did get me out of a few tight spots (the trail to Lion’s Back?).
   
4. Aussie v. Lock-Right quality. I do know that the Aussie is made right here in the U.S.A. from 9310 alloy steel because I helped set up the manufacturing here (they used to be made down under–-hence the name). I changed to 9310 from 8620 in about 1991 when I started to have chipping problems because 9310 has a higher nickel content that resists chipping. The industry seems to have attempted to follow suit until the last few years, but who knows what steel the Chinese are using? Also, heat treatment is a big issue. They may not now be heat treating the Lock-Right as well as was being done before. All I can say is that the Aussie is a first-rate product, and I can at least state my opinion that it’s the best of the “lunchbox” lockers out there. (That term originated in a magazine article about the Lock-Right in the early nineties, and it was thought up by the author.)
   
5. Axle rotation. An automatic locker will allow either wheel to rotate slower or faster than the ring gear. In a turn, power under acceleration is provided to the ground by the inside tire. This means that the outside tire has disconnected and is being ground-driven (rotating faster) than the inside tire, which is rotating at the same rate as is the ring gear. Less understood out there is deceleration. When getting off the gas in a turn, it turns out (pun intended) that deceleration is being provided by the OUTSIDE tire-–that is, the outside tire is the one connected to the engine and is rotating at the same speed as is the ring gear. This means that because the tires are rotating at different rates that the inside tire has to be going slower than the outside tire. Thus, the cam gear connected to the inside tire is releasing and making the “click-click-clicking” in the turn. The locker is a black box that only knows differences in rotation as power or deceleration is being applied. It doesn’t know forward or reverse or inside tire or outside tire.

[blackdiamond [OP]]

EMAIL 3
Being a Toyota guy, I think it’s really cool that the first L.A. Locker was for the Toyota 8” differential. Can you provide any additional information about why that became a problem that led to the name being changed to Lock-Right?

You previously said that because a selectable locker is a spool (when locked) it can put significant torsional strain on the axle shafts when turning on rock.  You also said that until there’s no torsion in either axle shaft the locker won’t disengage. This is all makes sense to me, but can you explain how things are different, or the same, with an automatic locker?  My experience in Moab with automatic lockers (Detroit Locker in the rear and Aussie Locker in the front) has been that my drivetrain will get bound up to the point of effectively locking my steering wheel and I simply cannot turn.  My automatic locking differentials have to be locked in these situations and I cannot imagine a scenario where what I experience could result in less stress overall compared to having selectable lockers that could be disengaged a large majority of the time. Are my automatic lockers not disengaging because there isn’t enough backlash available in those situations?

RESPONSE 3

Of all the timing that could have happened--just yesterday I found a slide dated 1989 that is probably the only photo in existence of the L.A. Locker at a show. This particular one was for the Suzuki Samurai (now L-R model 1510), but the first L.A. Locker (now L-R) for a one-piece differential case was model 1610 for the Toyota 8-inch (the Samurai has a two-piece case). I chose the name “L.A. Locker” because “L.A.” seemed more up-and-coming, while “Detroit” seemed more like the past. The Detroit people took exception to my choice because it supposedly was too close to their name, and they even claimed that they had a lock (pun intended) on the term “locker,” which I promptly disproved and shut them down on that score. My attorney said that it would be an easy win, but even so, fighting that battle would have taken more resources than I had at the time, so I changed the name. I’ll put this in print for the first time--the person who came up with the name “Lock-Right” was a guy named Richard Denny, who was a machinist at the shop where the L.A. Locker was being made. I thought it was a pretty good name and so I used it, and the rest is history. He went to that great machine shop in the sky more than 20 years ago, but many thanks, Richard.

The answer to the difficulty in steering question is that when two tires are connected together with a solid shaft they are both turning at the same rate (duh!). That is why with a selectable locker locked there has to be some “give” at the ground or something will break because the tires are rotating at different rates while the vehicle is turning. If you’re turning in a sandy parking lot with a selectable locker engaged, there will be a constant “hiss” as the tires slip on the sand. If you’re locked and turning on solid rock (why is your locker engaged?), both tires are effectively glued to the ground but are being forced to turn at different rates, which creates tremendous stress in the axle shafts until one tire slips (if it can). This condition also produces noticeable understeer in a turn because both tires want to go in the same direction and they are trying to force the front end to also go in their same direction.

This condition of binding up when turning on rock also occurs in a vehicle with two automatic lockers, except that instead of binding up side-to-side the axles will bind up front-to-back, which, of course, includes the steering. When turning on solid rock, both outside tires over-run and are not part of the equation. Both inside tires are providing power to the ground, but they are also directly connected to each other by the axle shafts, drive gears, drive shafts and transfer case. The turning radii of the tires are not the same (the back tire doesn’t follow the same path as the front tire), so with both tires rotating at different rates a lot of torsion will build up in these front-to-back driveline components. Eventually the friction in the moving parts will be enough to stop the vehicle (or break something). This is called “driveline windup” and was mentioned in my early L-R instruction manuals as being something to watch out for. When this binding up happens, the steering knuckle on the bound-up side can’t move either, which is why you couldn’t steer. In extreme situations the only solution is to jack up one wheel on the inside of the turn and watch it go “sproing!” to relieve the driveline tension. You can’t undo a hub or put the transfer case in 2WD because they won’t release due to the friction. About the only other solution is to either back up and slowly turn in the opposite direction or goose it and try to get a tire to slip. Although I haven’t needed to try this, it would seem that if you put a piece of smooth material in front of one of the tires and drive onto it that this would reduce bite at the ground enough to let the tire slip and relieve the tension. Vehicles with two selectable lockers locked will experience the worst of both worlds because they will bind up both side-to-side AND front-to-back, which means that the driver really needs to be observant about the terrain under his vehicle.

In this same turning scenario with open differentials you’ll get the same result, although it will take longer because the differential gears are also rotating so that the driveline torsion builds up more slowly. I’ll guarantee you that if you are in 4WD with open differentials on solid rock and driving in a circle that you’ll also get driveline windup, and either you’ll stop moving or something will slip or something will break. That’s why rule no. 1 with a 4WD vehicle is that you don’t drive in 4WD on pavement (and shouldn’t on solid rock either). Since driveline windup occurs more slowly in 4WD with open differentials, with a selectable locker the problem of torsion buildup in 4WD will occur less often IF the driver pays attention to his surroundings and turns it off when not needed(or selects 2WD).

Sorry if this got a little long, but I am glad that I could add my information to that of the other experts out there who are probably even more familiar than I am with the subjects I’ve covered. Just for my street creds-—I got my first 4WD vehicle in 1964 (back when I was really young), which was a WWII Ford GPW into which (for some unknown reason) I put a Studebaker flathead 6 engine. Yes, it did fit! Later on I had a ’48 CJ-2A to which I added a Warn overdrive. I’ve also owned a 1941 WWII Dodge 1/2-ton 4x4 panel truck and a 1942 WWII Dodge 3/4-ton 4x4 WC54 ambulance, to which I added a MoPar 360 V-8, an NP-435, a 2-speed 6x6 transfer case and 9-5/8 third members. This latter vehicle is the one for which I invented the All-Trac automatic locking differential in 1985, which then led to the L.A. Locker (later the L-R) in 1989 and eventually much later to the Torq-Locker (torqmasters.com). In 1993 I brought in two other people and formed PowerTrax, but three years later there was a hostile takeover and I left the company but stayed close to lockers. My last article was in the March, 2000 issue of Four Wheeler and is still on the internet (http://www.fourwheeler.com/how-to/29298-latest-locking-differential-technology/). My present ride is a 1992 Dodge W250 3/4-ton 4x4 pickup with a Cummins first gen diesel engine and a 1-ton drivetrain. It has a Spicer 60 in the front end with a prototype TorqLocker and a Spicer 70 in the rear with a production L-R, and a gear-driven transfer case. Of course, it’s a stick (so were all my others). For those of you familiar with what’s out west, I have a photo taken in 2015 of my dog and me and the Dodge and the sign at the top of Imogene Pass at 13,114 feet, between Telluride and Ouray, Colorado (my wife took the picture and really enjoyed getting high with me on that trip).

Hope my info helps. Happy four wheeling!

[Slabzilla]

Thanks, that was awesome info and straight from the horses mouth!  I now feel properly schooled.   

[blackdiamond [OP]]

That was some very interesting reading and what a cool guy for taking the time to answer your questions. man, that guy is a legend

I certainly wasn't expecting that I would receive this level of interaction when I contacted Torq Masters. I have had several more emails with John but I tried to keep the information in this post very focused. I think my understanding prior to this would have been above average, but I was wrong on several things that surprised me. What's most fun for me is the new information really explains what I feel when driving.

[85Buckett]

Great read here ... I'd vote this to be a sticky by reading it one can learn a lot on drive-line wind-up and how to take precautions with  front and rear automatic lockers in a vehicle. 

[blackdiamond [OP]]

One aspect that I had previously inquired about with John Zentmyer is how the pins function within the automatic locker assembly and why they break.  The topic came up briefly yesterday and reminded me that I hadn't followed up on it.  John and I have had several emails in the past weeks, it surprises me every time he sends me an email unprompted to continue our discussion.  Here is his response from today to my question about the pins:

EMAIL 4
Can you explain how the pins function, get loaded, and can break?

RESPONSE 4
The pins were originally called stop pins, and may still be. They prevent (stop) the over-running driver (I don't like the name "cam gear") from rotating past the amount of clearance needed for it to unlock--that is, slightly away from the pinion shaft, so it can be pushed out of the teeth of the coupler (axle gear). In ordinary operation, the stop pins have very little force imposed on them. However, they can break under two conditions: (1) If a small piece of metal, such as a chip off one of the teeth of the drive gears, gets caught between the drivers during uncoupling, the driver associated with the faster wheel can't completely disconnect itself from the coupler, so the turning force is transmitted to the pins and they break, and (2) when climbing up a steep hill with a lot of torque on the axle shaft, if the shaft breaks, its inner end that was under a lot of torque, but isn't any more, snaps the coupler really hard when it lets go. With things whipping around in there the pins will sometimes break.