Locking Diff?

[cruiser54]

1 minute ago, pizzaman09 said:

I'm mostly commenting as this was a very interesting read from an off roader point if view.  I've done a lot of autocross racing with various LSDs.   I've run stock 25% lock up plate style LSDs in a BMW M5 and M3.  I went with a Quaife torsen LSD in my Mini.  Between the two different types on the race track, they both feel the same.  The Mini originally had an open diff and the torsen diff made a world of difference.  Being 2wd vehicles, the LSDs were worth their weight in gold in the snow.

When I do pick up my next Comanche someday, I will likely be going the torsen style diff route for it.  

Good luck finding one. 

[pizzaman09]

3 hours ago, cruiser54 said:

Good luck finding one. 

Thanks!  I had one and completely regret selling it.  I'll find the perfect one and am able to weight to find it.  Looking for the dream 4.0L, 5 speed, 4x4, short bed, sport truck with AC, preferably in white with hockey stick graphics. 

[cruiser54]

You had one for a Dana 35?

[Pete M]

is this what we're talking about?

 

https://torsen.com/product/ford-ranger-dana-35/

[gogmorgo]

Many people refer to all types of helical-gear limited slips as “Torsen” diffs, not realizing it’s a brand name. I know otherwise, as I’ve personally dealt with the T1. Reassembling that sucker is a PITA but once it’s together it’s a great diff. I know Cruiser has a connection to the company as well from prior posts. 

 

[cruiser54]

56 minutes ago, Pete M said:

is this what we're talking about?

 

https://torsen.com/product/ford-ranger-dana-35/

If they had one for a Dana 35 rear in a Jeep, they would list it. 

[cruiser54]

25 minutes ago, gogmorgo said:

Many people refer to all types of helical-gear limited slips as “Torsen” diffs, not realizing it’s a brand name. I know otherwise, as I’ve personally dealt with the T1. Reassembling that sucker is a PITA but once it’s together it’s a great diff. I know Cruiser has a connection to the company as well from prior posts. 

 

Yes. My friend's Dad invented the original Torsen and I worked for Gleason Corporation. 

[Pete M]

I would have thought that too so I guess it's nothing. 

 

they do list the 44 though  

[ghetdjc320]

Ok I’ll throw in my $.02 

I’ve had 3 Detroit Truetracs and they’ve all done very well on the street but are only a bit better than open off-road. It’s not like it’s 50% better and half way between open and locked. More like 25% better I’d say. However I do prefer them greatly on wet or slick roads as they help the rear of the truck to track much better and feel more consistent and predictable. Most of the stories we hear about actual Detroit lockers being difficult to drive are on much shorter wheelbases and manual tranny vehicles. I’d say that on a longer wheelbase  vehicles like an MJ (swb or lwb) they are much more docile. Especially with an auto tranny as the torque converter keeps the shifts consistently “soft”. Unless you throw in a transgo kit like I’m about to do 

[gogmorgo]

Yes. It’s definitely a limited slip, not a locker, but they’re significantly better at limiting slip than a clutch-type differential. Other advantages are significantly longer service life and not needing friction modifier.

Unless you’re doing a lot of wheel lifting offroad, rock crawling, etc., I’d have to say that 95% of the time a limited slip is better than a true locker. Less effect on steering, less damage to the trail from skidding tires, etc. It’s also easier on the vehicle due to reduced binding in the drivetrain, less tire wear, etc. And I wouldn’t really trust a full locker in a D35 of all axles... But yes, when you NEED a locker, you need a locker, and a helical-gear limited slip diff is still a limited slip diff, not a locker.

 

As far as what’s the best helical-gear limited slip, the Truetrac is easily the most common. It’s even OEM in a bunch of applications. It’s more affordable than the original Torsen but not the most affordable of its type. There’s a PowerTrax(?) branded thing out there now that is significantly lower priced, to the point when I was researching before settling on the Truetrac for my ZJ a couple years ago, I dismissed the PowerTrax as being too cheap to be real.

I also looked very close at the Ranger d35 Torsen unit. IIRC, the specs seemed bang on between Ranger and Jeep carriers, but I couldn’t quite bring myself to throw down the extra coin for it when the voice in the back of my head (well, one of the voices...) kept asking why would they miss out on such a big market as a Jeep D35 that went into every Jeep built for almost a 25-year period, if it would be compatible. And yes it’s a lot of coin extra because I couldn’t find a Canadian retailer to avoid crazy shipping charges on it, unlike the TrueTrac. Oddly enough however, I just stuck a new ring and pinion in my ZJ d35, and when the parts numbers didn’t match to between the new and old gears, I looked them up with Dana, and the gear set that was in it actually lists for the Ranger. They looked identical to me, but the old ones were pretty beat so it’s tough to say. 
Also as a pro tip, for anyone adding a fancy diff to a D35, make sure your gears are set up correctly for the new one instead of just putting all the shims in the same place you found them and hoping for the best, like this idiot did. I had maybe 3000 miles on it before the gears started letting me know they were very upset. And my very expensive d35 is now a VERY expensive d35.

[ghetdjc320]

I picked up my last truetrac for about $300 on Amazon. They are made overseas and prices are all over the place. You have to have a decent amount of resistance for it to work so it’s just very subjective results depending on where you wheel. I really liked the idea of the rear TJ rubicon lockers. Gear driven lsd and air locker in one. Really nice combo I ran twice, once in a rodeo D44 I built for my YJ and later in my 05 TJ rubicon. It was said to have issues with air leaks and keeping a good seal but mine always worked with no issues 

[cruiser54]

Most Torsens will not work with C-clip axles. At least the original cross-axis originals.

That could be a deal breaker. Not sure about what other products got added to the line over the years that aren't the true Torsen design.

[1989commanche]

I have the Eaton TruTracs in both axles in my Comanche. Have got me everywhere I’ve pointed it. 

[Eagle]

On 2/20/2014 at 6:56 PM, Megadan said:

Yes, but even Helical limited slips like the Truetrac have advantages and disadvantages.  They are never a positive engagement like a clutch type would be, and as a whole they behave more like an open diff than anything else mentioned.  For example, if you have the wheels off the ground and spin one by hand, the other will spin opposite since the gears aren't under enough load to cause the diff to engage.  They are great for on-road use, but unlike a clutch type limited slip or a locker, if one wheel spins on a slick surface, it will actually keep spinning (although, the other will get some power at least). 

 

I have to disagree. I own three Cherokees with the factory TracLok (clutch type) limited slip, and I owned several pony cars with clutch type limited slips before the Cherokees. I put a TrueTrac in my '88 MJ and there's no comparison. The TrueTrac is quieter, and engages much more securely and firmly.

[derf]

8 hours ago, Eagle said:

 

I have to disagree. I own three Cherokees with the factory TracLok (clutch type) limited slip, and I owned several pony cars with clutch type limited slips before the Cherokees. I put a TrueTrac in my '88 MJ and there's no comparison. The TrueTrac is quieter, and engages much more securely and firmly.

Yeah, my XJ with the TrashLoc from the factory was decent for the first couple of years.  But by the time I trade it in it wasn't any better than an open differential.  I had the same problem with an Auburn Gear ECTED (clutch type limited slip that has an electronic "locker" that doesn't actually lock the axles).  They help a little when you have tires touching the ground with some weight.  But start to lift a tire and the clutch type limited slip does nothing.  In short order, you wear out the clutch packs and they don't limit slip at all.  And I don't like the idea of having a diff full of grit from the clutch packs, or the idea that the differential is a wear item that needs to be serviced.

 

I have TrueTracs front and rear in my XJ.  They are great for on road manners and they do help on moderate trails with 4 tires on the loose ground better than any clutch type limited slip.  Sure, they will let a tire spin when it's up off the ground just like any limited slip, but they are quite a bit better than the clutch type in all other respects.

[Eagle]

11 minutes ago, derf said:

 

I have TrueTracs front and rear in my XJ.  They are great for on road manners and they do help on moderate trails with 4 tires on the loose ground better than any clutch type limited slip.  Sure, they will let a tire spin when it's up off the ground just like any limited slip, but they are quite a bit better than the clutch type in all other respects.

 

That's a rare situation. When it happens, all that's needed to make it lock up is a light touch on the brakes.

[derf]

14 minutes ago, Eagle said:

 

That's a rare situation. When it happens, all that's needed to make it lock up is a light touch on the brakes.

Where I go, it's not as rare as you might think.

[DesertRat1991]

I run a TrueTrac in front and an e-locker in the rear. I'd estimate my truck sees 70% street use and the rest has been a mix of silt, sand, gravel, mud, water crossings and slick rock.  So far this setup has gotten me everywhere I've wanted to go. 

 

Maintaining good street manners was a top priority for me so ratcheting, quirky lunchbox lockers were a no-go.  In 2wd (no torque to TT) with the rear locker off, the truck rides smoothly with open/open diffs.  In 4wd, with the rear open and both front wheels pulling together the TT helps me feel much more in control when travelling through deep sandy washes at speed.  It also helps a lot on steep, loose inclines.  With the rear locker on and front TT doing work she crawls like a tank.  I also like having access to 2wd locked mode which is usually the fastest and easiest way out of most slippery situations.   

 

But, but... "What about lifting wheels off the ground?"  I agree with Eagle.  Whenever I hear this I can't help but chuckle.  Makes me wonder: 

 

1) Who are you? 

2) And, how often do you actually lift a wheel off the ground?

 

If your answers are:

1) King of Hammers Champion

2) Or, "Frequently"

 

Then you shouldn't even be considering an LSD, just get a locker.  You'll be way happier.  For everyone else, a TT will get you places.  When a wheel lifts off the ground the weight transfers to the other 3 wheels.  Pairing the TT with a locker is a good solution that will allow you to push/pull your way out of those scenarios. 

[derf]

My XJ is my daily driver/mild trail rig.  It has TrueTracs front and rear.  It will almost never see a tire fully off the ground.

 

For my rock crawling rig, the one that will see tires in the air on a quasi-regular basis, selectable lockers are the only answer for me.  Automatic lockers and spools are preferred by others and they get the job done as well but they're not for me.

[ghetdjc320]

To say that the truetrac’s only shortfall is when a tire is in the air may be an understatement. The truetrac doesn’t know when a tire is in the air, it’s just sensing resistance. I’ve had it sit there spinning one wheel in mud or one wheel spinning on some slick rock. What I like about the truetrac is that it helps track more predictably on-road. It can help a squirly truck have a bit more traction and it’s cheap. It provides minimal more traction though off-road. It has no air or electric lines to deal with and it is easy to turn with. So there are plenty of pros but, it’s a full case swap and will require setting your backlash and preload properly. You should be able to leave your pinion depth alone unless it was out of spec to begin with. By the time you go to all that work you may regret not going with a selectable for a few hundred more. Basically you already did 90% of the work but only gained maybe 25% more traction. 

[gogmorgo]

The Truetrac, and any other limited slip diff, has a torque biasing ratio. Actually, all other diffs do as well.

An open differential is 1:1. This means that whatever torque one wheel is seeing, the other will see the same torque. If the torque it takes to spin one of the tires isn’t enough to move the vehicle forwards, you won’t move forwards. A limited slip alters the torque bias. Depending on the model, a Truetrac could be as much as 3.5:1. This means that it’s going to bind up so that it pushes 3.5 times as much torque onto a “stationary” wheel as it does on the free-spinning wheel. 50ft-lbs of torque to spin the tire puts 175lb-ft into the stationary wheel to push you forwards. And yes, if that’s not enough to move you forwards, it’ll just keep spinning the one wheel. When a wheel is in the air it takes next to no torque to turn it, and three times almost nothing is still not much more than nothing. 

A locker could be seen as having an infinite:1 bias ratio. The shafts are locked together, or at least to the carrier, so really it stops being a differential at that point. It doesn’t matter how much torque it’ll take to turn either wheel, the other will always turn at the same speed.
 

It’s also not entirely true to suggest the Truetrac doesn’t have a wear life. You hear sometimes that it functions through the principal of a screw gear can turn a worm gear but a worm can’t turn a screw, which isn’t what’s happening. What’s happening is that helical gears thrust themselves away from each other axially, essentially parallel to the shaft they’re on, and this forces the helical gears into the side of the housing, which then slows down the helical gear. The bigger the difference in wheel speed, the harder those gears get rammed into the housing, and vise-versa, which is why it’s so invisible and seamless in operation. And that’s where the wear life comes in, eventually the gears cut themselves into the side of the housing. I’ve seen it happen on a unit with about 200,000 miles on it. Not terrible life I suppose, though. Spider gears eventually wear out too.

The original Torsen T1 with its crazy (and very difficult to manufacture) helical gears that run 90° to each other jam the whole side gear into the carrier, which gives it more surface area, so it’ll bind up much harder. They also use clutch packs in the middle of that to increase traction even further, and those clutches will burn out. Not as quick as a clutch-type LSD but they do go eventually. Torsen tells you they’re not serviceable, but if you’re really keen you can pull it apart and change them. I’ve done it. It sucks. The crazy gears all need timed in a very specific set except you can’t actually see the timing marks once they’re installed, and you can’t install them straight in, so you have to set everything up perfectly with the timing marks completely misaligned and then roll everything together all at once so the marks meet up. And if any one of the gears is off by one tooth once they go together, the whole thing locks right up, and you end up with a very complicated and expensive spool that you need to pull all the way back apart and start all over. Not much fun at all.

[cruiser54]

As a user of the Torsen 1, and working with the company (Gleason) back in the 80s, the unit had no clutches. didn't need them.  And it doesn't "bind". I had units both front and rear in my Nissan Patrol and Jeep full size Cherokee Chief equipped with Quadratrac, The Cherokee was my demo vehicle for the most part. 

[ghetdjc320]

On 9/4/2020 at 12:34 PM, gogmorgo said:

 

A locker could be seen as having an infinite:1 bias ratio. The shafts are locked together, or at least to the carrier, so really it stops being a differential at that point. It doesn’t matter how much torque it’ll take to turn either wheel, the other will always turn at the same speed.
 

 

That’s the case with most selectable lockers but not auto lockers. 

[gogmorgo]

No, if it’s locked, it’s the case. Not all of them act quite like a typical differential when unlocked, and not everything locks under the same conditions, but anything locked effectively has an infinite:1 torque bias.

[cruiser54]

Remind me sometime and I'll do a post on torque bias. I may have it saved somewhere.