LSD for Automatic (U340E)

[06YarisRS]

Found this and am hoping someone with experience with this type of stuff could comment. From my research, it doesn't seem like a true LSD, but a straight line locker. I would not be tracking my car but I'd also be unhappy with any kind of binding in slow turns. I think it's supposed to unlock if it senses different wheel speeds - aka, a turn. I find my 2ZR a bit 'spinny' if I'm not careful taking off.

EDIT: The more I read about these conversion kits, the more sceptical I become. It sounds like they have the potential to damage running gear and don't offer many of the benefits of a true LSD. Still interested in opinions though.

https://www.tractionconcepts.com/Toy.../tcxty4900.htm

[CrankyOldMan]

There really isn't a substitute for a proper LSD. The labor involved in installing an LSD dwarfs the price differential of a genuine unit and the imitations. Basically, you need to be able to clear at least US$1200-1500 for parts if you're serious about having one. Figure another thousand plus if you can't install it yourself, and you'll need to find someone you trust to do the work right. ArmstrongRacing is/will be offering custom Yaris gearbox work.

If you want to go it alone, you have to pull the trans, remove the guts, swap the ring gear, replace all the seals, and be able to put it all back together. Removing the 5th gear set requires a quality bearing puller (US$150-250). The only tricky part of the install is setting the bearing preload but there are many ways to accomplish that other than a US$1500 in-oz torque wrench.

I've had a Quaife helical for over 5 years now and have been very happy with it, even in snow and icy conditions. ArmstrongRacing has used Cusco clutch type for a few years now and has nothing but positive comments.

The alternative, of course, is to get tires with better grip. =)

[06YarisRS]

Originally Posted by CrankyOldMan

There really isn't a substitute for a proper LSD. The labor involved in installing an LSD dwarfs the price differential of a genuine unit and the imitations. Basically, you need to be able to clear at least US$1200-1500 for parts if you're serious about having one. Figure another thousand plus if you can't install it yourself, and you'll need to find someone you trust to do the work right. ArmstrongRacing is/will be offering custom Yaris gearbox work.

If you want to go it alone, you have to pull the trans, remove the guts, swap the ring gear, replace all the seals, and be able to put it all back together. Removing the 5th gear set requires a quality bearing puller (US$150-250). The only tricky part of the install is setting the bearing preload but there are many ways to accomplish that other than a US$1500 in-oz torque wrench.

I've had a Quaife helical for over 5 years now and have been very happy with it, even in snow and icy conditions. ArmstrongRacing has used Cusco clutch type for a few years now and has nothing but positive comments.

The alternative, of course, is to get tires with better grip. =)

Wow, very informative, Sam. There are certainly other areas that I'd prefer to spend that kind of money. I had no idea it was so involved. And, and job like that is way beyond my current skill level.

So, is the one I linked to just junk? Let's say that I just wanted equal traction on both wheels while going straight, would the one I linked work? What I wonder about is how it knows when to unlock. It says it engages under high load, but if say I was coming out of a turn under moderate throttle would it suddenly engage, causing a wheel to slip? And, would it be truly unlocked when driving around in slow turns, or would it be tight and bind somewhat?

[CrankyOldMan]

I can't say for sure that it's junk, but my engineering senses tell me that it's orders of magnitude less effective than a proper LSD. Here's a summary that mirrors my opinion and gives some thought to the physics of that type.

I think his (her?) summary at the end is spot on: for what it takes to do the conversion, the extra cash for the proper diff is the least of your problems. And as far as skill level goes, I did my gearbox build years ahead of my engine swap. I also practiced 3 times on parts donors before attacking the actual gearbox, so that helped.

As for the actual performance? No idea. A clutch type uses the friction disks to create a threshold for "opening" the diff, a helical uses the slip angle of the gears to do the same. This one is just pushing against the spider gears on the smaller end of their tapered teeth, so the contact patch is tiny. I can't find any definitive/conclusive evidence that they in fact improve traction, just marketing videos and people whose butt dyno swears that they make them faster.

[06YarisRS]

Originally Posted by CrankyOldMan

I can't say for sure that it's junk, but my engineering senses tell me that it's orders of magnitude less effective than a proper LSD. Here's a summary that mirrors my opinion and gives some thought to the physics of that type.

I think his (her?) summary at the end is spot on: for what it takes to do the conversion, the extra cash for the proper diff is the least of your problems. And as far as skill level goes, I did my gearbox build years ahead of my engine swap. I also practiced 3 times on parts donors before attacking the actual gearbox, so that helped.

As for the actual performance? No idea. A clutch type uses the friction disks to create a threshold for "opening" the diff, a helical uses the slip angle of the gears to do the same. This one is just pushing against the spider gears on the smaller end of their tapered teeth, so the contact patch is tiny. I can't find any definitive/conclusive evidence that they in fact improve traction, just marketing videos and people whose butt dyno swears that they make them faster.

Phantom (def): a figment of the imagination. Thanks for the article. I definitely makes sense. Since a true LSD is unlikely to make its way into my Yaris, I think a fraction of what it would cost could go toward a better set of more 'grippy' tires, as you suggested.

[suprf1y]

Originally Posted by CrankyOldMan

As for the actual performance? No idea. A clutch type uses the friction disks to create a threshold for "opening" the diff, a helical uses the slip angle of the gears to do the same. This one is just pushing against the spider gears on the smaller end of their tapered teeth, so the contact patch is tiny. I can't find any definitive/conclusive evidence that they in fact improve traction, just marketing videos and people whose butt dyno swears that they make them faster.

Options for the Suzuki's I used to drive is limited so these are fairly popular, and though it's not the real thing, the guys who use them really like them.

Probably better than nothing IMO.

[06YarisRS]

Originally Posted by suprf1y

Options for the Suzuki's I used to drive is limited so these are fairly popular, and though it's not the real thing, the guys who use them really like them.

Probably better than nothing IMO.

Interesting. Thanks. I've been doing more reading. Although I'm just learning about differentials, the idea of direct metal-to-metal contact and high outward forces on the axle gears would worry me. I understand how important it is to have the axle gears shaved to have a uniform surface between the PG plates and the gear, but I've seen a few pics of extreme wear and damage. I've also read many, many positive reviews. Just not sure it's a gamble I'd be willing to take.

[suprf1y]

The operation of differentials and final drives is based on metal to metal contact under high loads. I wouldn't let that deter you.

[06YarisRS]

Originally Posted by suprf1y

The operation of differentials and final drives is based on metal to metal contact under high loads. I wouldn't let that deter you.

Thanks. Yeah, I'm still in the learning phase. It makes sense that there would be metal to metal contact on gears etc. I just made me wonder about the outward force on the gears and possibly the housing. Since it was not originally engineered that way, the springs of the locker would be exerting forces not originally intended. Or, maybe I still just don't understand how it all works.

[CrankyOldMan]

Originally Posted by suprf1y

The operation of differentials and final drives is based on metal to metal contact under high loads. I wouldn't let that deter you.

Contact, yes, but not necessarily the same kind. A helical is called a helical because it uses multiple hypoid profile helical twist gears to transmit the power from one side to the other. A hypoid gear tooth profile is based on a continuously moving contact point, but the actual metal of one gear is not moving relative to the other gear. A clutch type has friction materials that slide against each other when it breaks free but is otherwise not sliding. The phantom has sliding metal any time there is a differential in speed between the axles and both tires have static contact with the road, i.e. turning on dry pavement. Even with a coating of gear lube, that's not my idea of a recipe for longevity. =)

[BIGTAZ351]

As I understood those the OP linked to be, the FWD equivalent of a "Lock Right" or as we used to call them "Lunch Box Lockers" they are very crude and pop and bang sometimes which I hardly notice in the rear of my 4x4 truck, but would make me uncomfortable in my U340E! (Sorry for run on sentence, I am on my phone)