Anyone out there running front & rear LSDs?

[MODist]

I think the bases have been covered here. LSD is great in sand, gravel and snow. Front and rear LSD's are no problem (I have driven a number of subarus with this setup and the traction is impressive, and spent a lot of time in FWD LSD cars in the snow). Once a wheel goes in the air, they're about as useless as open diffs. So if that type of wheeling is not in your repertoire, I see no reason not to try it.

Not all LSD's are the same. Friction plate LSD's are a small step above open. Gear driven LSD's are far more effective. I've had two wheels off the ground multiple times in my Bronco and it was no problem. I did the same with my wife's Navigator and it struggled with open diffs and traction control.

Here is a short clip with one wheel off the ground. It looks like I'm stuck but the actual problem was the front end lift. Before the video started it was about a foot higher and all I could see was the tops of the trees. There was some driveline torque that was causing the front end lift. I was babying it trying to inch forward.

3 wheeling

 

[BILT4ME]

I had a 69 Chevy half ton 4x4 with Eaton clutch type LSD front and rear. I ran 4.10 gears and had a 375 HP 350 with 4 speed and locking hubs in front. 33" mud tires.

In.slick mud I had a hard time turning because all 4 wheels turned the same speed. Same on snow and ice. The truck was unstoppable in deep anything and was used to pull out loaded semis, dump trucks, and tow trucks.

If I were doing it again (and I am) I am installing a Detroit Locker in the rear to handle the HPand torque and will install a selectable locker in front for those times that I MUST have the extra boost.

I used the truck as a DD and for the most part it was OK. It would get a little squirrelly in heavy traffic with slick spots on pavement. I wanted to run with hubs locked in and in 4WD, but it tended to drift lanes in turns if it was slick. I started driving it with only one front hub locked and it helped to stabilize it in these conditions, but was useless if I really needed all 4 wheels pulling.

I look at.my LC as if my wife would be driving it. I will install a locker in the rear so it's there all the time. Then install a selectable in the front so if she would get stuck, she'd call me, and I'll tell her to engage the front locker to get out, then disengage again as soon as she's free. This way, it's kind like going in in 2WD, then engaging 4WD after you get "stuck".

To me, that's the best of both worlds.

Good luck!

 

[SkyMall]

I had a 69 Chevy half ton 4x4 with Eaton clutch type LSD front and rear. I ran 4.10 gears and had a 375 HP 350 with 4 speed and locking hubs in front. 33" mud tires.

In.slick mud I had a hard time turning because all 4 wheels turned the same speed. Same on snow and ice.
Good luck!

I don't mean to pick a fight, but I'm not sure about this. What you're describing is a locked front and rear, not LSDs. I suppose if the clutches were packed really tight it could be squirrely, but front/rear LSDs is what Subies run and they're the opposite of squirrely.

 

[BILT4ME]

No, anything with a clutch pack in the differential is a Limited Slip Differential. This means it will allow some slip for cornering and one wheel must spin some before it engages or locks. Review the attached link for more descriptions.

The Spool, Detroit Locker, ARB Air Locker, and similar "selectable" lockers are locking differentials. They have teeth that engage and are fully engaged when selected, or full time in the Detroit Locker.

The Ford or GM limited slip fluid (friction modifier) added to differentials with clutch pack type LSD's is to allow the clutch packs to slip without smoking them or the oil. The friction modifier actually makes the oil MORE slippery in order to allow the LSD's to NOT be as tight.

The very first time my LSD released in a low speed corner, it sounded like someone hit the differential with a sledgehammer. That's actually a requirement after you get it installed and have the modifier in there in order to coat the plates with the oil. Otherwise it's too "tight".

And yes, I have blown out an Eaton Posi (LSD) 4 times in that truck because the slip allowed momentum to increase in one wheel in a low traction condition while the other wheel was on dry pavement. (33" mud tires and 375 HP). It engaged and blew up the spider gears.

The Detroit Locker is a heavy duty, square-tooth gear that is engaged in another gear with a spring forcing them together. Only in low speed, low torque conditions does it allow the two gears to disengage. That is the clicking that people talk about hearing when going around corners.

Traction control and torque control using Eaton differentials

No offense taken. This is an open forum. DO some more research about the differences between the Locking Differentials and LSD's.

The other one I really considered was the Detroit TrueTrac. It has some really cool features and I may consider it for a front differential if I want one that I don't have to touch.

If you are rock crawling, you SHOULD have a locking differential because you may frequently have a wheel off the ground. An LSD will allow that wheel to spin if there is enough traction at the wheel on the ground.

The TYPE of differential should be governed by the intended use of the vehicle.

Good Luck and let us know what you end up doing!

 

[BILT4ME]

I should also add that you need to what TYPE of LSD the Subaru has in it. It may be a viscous coupling LSD, that with enough RPM, it will engage the other wheel enough to help it move forward. The Subaru is a nice slick road AWD, but it is NOT an off-road vehicle. The LC and the Subaru are very different use vehicles.

 

[SkyMall]

I agree that a LC and a Subie are built for different purposes, but in base form their AWD systems are not that different. They both have a viscous coupling center diff and open front and rear diffs. Some Subies have a rear LSD and the type depends on the application and the year - whether they are helical or clutch type. I did a little digging and I was mistaken. I don't think any of them came with a front LSD of any kind. My Subie/Cruiser comparison was just for on-road manners, in which case the major differences in stock version of most variants are tires, weight, and balance.

That being said, I was just commenting on your statement that with front and rear LSDs, "In.slick mud I had a hard time turning because all 4 wheels turned the same speed. Same on snow and ice." I'm not sure what you meant to say, but having a limited slip in between your wheels by definition means that all four wheels can and do spin at different rates. I'm assuming that what you meant to say was that the front and rear driveshafts spun at the same rate since it was a part-time 4WD system without a viscous center diff, in which case I agree it's tough to turn on dry pavement in 4H or 4L. My old 4Runner was that way and it had open diffs in the front and back.

 

[SkyMall]

Thanks for the link to the Eaton website. I think that was the only page of theirs that I HADN'T explored. Haha! I'm not sure if you read the whole thread, but the initial question I was asking was what experiences - good or bad - have people had with a front/rear LSD setup in a Land Cruiser, because I was looking for a way to have a totally passive system that would be a good improvement in any condition where I wasn't lifting a tire. I have a 1994 that came from the factory with a SF rear end and there wasn't a selectable locker available except the ARB and I am not interested in their product.

I recently found a FF rear end and it's being installed as we speak. The next phase of my build will be front and rear end rebuilds with a TrueTrac up front and a Harrop out back. That should give me the best possible road manners and on-road traction, PLUS enough one-wheel-off-the-ground traction if I ever need it.

 

[SkyMall]

Here are a couple videos that explain torsen type and LSDs and why they sparked my curiosity. Having watched them both, it appears that the Eaton design is quite a bit different, using all gears that rotate in the same plane. Anyone have thoughts on this?

 

[BILT4ME]

I agree that a LC and a Subie are built for different purposes, but in base form their AWD systems are not that different. They both have a viscous coupling center diff and open front and rear diffs. Some Subies have a rear LSD and the type depends on the application and the year - whether they are helical or clutch type. I did a little digging and I was mistaken. I don't think any of them came with a front LSD of any kind. My Subie/Cruiser comparison was just for on-road manners, in which case the major differences in stock version of most variants are tires, weight, and balance.

That being said, I was just commenting on your statement that with front and rear LSDs, "In.slick mud I had a hard time turning because all 4 wheels turned the same speed. Same on snow and ice." I'm not sure what you meant to say, but having a limited slip in between your wheels by definition means that all four wheels can and do spin at different rates. I'm assuming that what you meant to say was that the front and rear driveshafts spun at the same rate since it was a part-time 4WD system without a viscous center diff, in which case I agree it's tough to turn on dry pavement in 4H or 4L. My old 4Runner was that way and it had open diffs in the front and back.

Actually, my statement is correct. The DIFFERENCE in friction between all four wheels is negligible, so all four do, indeed turn the same speed. The reason you can turn is because of friction between the tire and ground and the different speed is due to the different turn radius. When you have near zero friction, the tightness of the LSD cannot be overcome by the friction of the tires because it is minimal. Therefore they all turn the same and you cannot turn due to lack of friction.

I think you will have an excellent setup with that combination in front and rear. The only thing I would do I'm addition is to add locking hubs, but that's a personal preference for me to keep the front isolated during normal driving.

I like the torsen differential for the front and you can use the brakes to force this into a near locked condition in the event of a lifted wheel.

 

[scottryana]

My next combo is going to be Trutrac up front and Detroit in the rear. Simple, tough to break, and quite a bit more capability than stock. My other LX will get the factory locked axles out of this truck.

 

[Elbert]

I had two auburn LSD's in my 60 for some time, obviously its not full time 4wd. I liked the auburn units and thought they were well made and I had no issues with the quality or operation. My view is this...LSD is good for pavement (snow /ice) dirt roads, mud, and for hot-rods. LSD is not good or optimal for rocky conditions where you do not want tire spin. I'll say this...in the long run your best money spent is to get ARB selectable lockers. Depends on where you drive your truck but LSD is not a good solution for rocky conditions where you don't want tire spin. I don't think it would be an issue to have an Auburn LSD in the front of a 80, as noted in other threads there are other vehicles out there that run LSD in full time 4wd, both in the front and rear. Running around on the pavement you really only notice the Auburn unit in the rear on hard truns in slow speed on pavement...you'll hear the tire noise a little more from the LSD operation.

 

[SkyMall]

When you have near zero friction, the tightness of the LSD cannot be overcome by the friction of the tires because it is minimal. Therefore they all turn the same and you cannot turn due to lack of friction.

AHHH!! OK, that makes sense. I see what you're saying now. I was thinking conceptually and you were speaking practically.

 

[SkyMall]

I had two auburn LSD's in my 60 for some time, obviously its not full time 4wd. I liked the auburn units and thought they were well made and I had no issues with the quality or operation. My view is this...LSD is good for pavement (snow /ice) dirt roads, mud, and for hot-rods. LSD is not good or optimal for rocky conditions where you do not want tire spin. I'll say this...in the long run your best money spent is to get ARB selectable lockers. Depends on where you drive your truck but LSD is not a good solution for rocky conditions where you don't want tire spin. I don't think it would be an issue to have an Auburn LSD in the front of a 80, as noted in other threads there are other vehicles out there that run LSD in full time 4wd, both in the front and rear. Running around on the pavement you really only notice the Auburn unit in the rear on hard truns in slow speed on pavement...you'll hear the tire noise a little more from the LSD operation.

Yup. That's why I decided on the TruTrac/Harrop combo. I'm not at all interested in an ARB setup. It's expensive and does nothing for me on dirt, gravel, sand, wet/icy roads, etc. It's really only a crawling solution and that's not my style.

 

[SkyMall]

My next combo is going to be Trutrac up front and Detroit in the rear. Simple, tough to break, and quite a bit more capability than stock. My other LX will get the factory locked axles out of this truck.

I was going to do a TrueTrac/Spartan combo until I got the FF rear end. I'd like to keep the rear end open in normal driving conditions to preserve the on-road manners.

 

[scottryana]

A detroit and spartan basically act the same, except the detroit has a stronger carrier. Do you mean with a FF you now have more options so you are no longer thinking about an Auto rear locker? I have a spartan rear now and I do not notice any bad on-road manners in moral driving conditions.

I was going to do a TrueTrac/Spartan combo until I got the FF rear end. I'd like to keep the rear end open in normal driving conditions to preserve the on-road manners.

 

[SkyMall]

Do you mean with a FF you now have more options so you are no longer thinking about an Auto rear locker?

Yeah, I wanted to avoid an autolocker but the only selectable locker for a SF rear end is the ARB which I didn't want. The Harrop eLocker only fits the FF rear end, which I now have

 

[larry butler]

I remember LSD. That was way before I was engaged.

 

[woodsman 44]

I had an 85' toy SB truck with a true-trac in front and detroit in rear, awesome combo but Detroit is Brutal on-road manners, I would only go air or E-lock in rear....

 

[Jeepster09]

My next combo is going to be Trutrac up front and Detroit in the rear. Simple, tough to break, and quite a bit more capability than stock. My other LX will get the factory locked axles out of this truck.

This is the setup I have used without issue in my Jeep Cherokee and Wrangler.