Lockers vs. TruTrack

[ChrisInVT]

So what's the thought on the LSD of the Ford 8.8 rearend compared to the other LSD's?

 

[brianjwilson]

So what's the thought on the LSD of the Ford 8.8 rearend compared to the other LSD's?

The factory limited slip in there is a trac-loc, clutch based limited slip. It is better than an open diff, but the clutches wear out (they can be rebuilt somewhat tighter), and you can still sit and spin one tire that is in the air. Or if one tire is stuck, it may sit there while the other one spins. If you gas it hard on wet pavement or ice/snow, sometimes both will spin and oversteer, sometimes you'll light just one tire up... Which is why I would rather have an autolocker than a clutch limited slip, atleast the autolockers are predictable.

Still, it is much better than an open diff, and worth using if it's already in an axle that you're swapping in, but has it's limitations off road for sure.

 

[Ruffin' It]

Great clips, thank you.
It was obviously a sales pitch and they were certainly throwing softballs to the ARB's, but the point still holds.
Since the Toyota LSD hardly did anything at all to transfer torque to the other wheel, I assume that stock LSD is a clutch-type which is no where near as good as a gear setup. And Toyota's traction control must really be crap. I've walked up worse rutted inclines with two wheels in the air in my Rover using traction control without much drama and have freed myself from being frame deep in sand in a similar amount of time that it took a fully locked jeep to do the same, but again, lockers are obviously better in many low traction situations.
I'll still take traction control for rain and ski trips though. : )

For those home viewers who like to watch video examples, here's a good comparison using 3 traction variants in the same vehicle (Toyota Prado):

One with a rear LSD
One with electronic traction control
One with ARB air lockers.

http://www.youtube.com/watch?v=C2wkW05Pc6c&feature=channel

and part 2:
http://www.youtube.com/watch?v=YNFacsKnswM&feature=channel_page

These point out good safety benefits and also vehicle control of one over the other. It definitely doesn't take much for an LSD or traction control to be quite ineffective offroad. If you're keeping the tires on the ground, then you'll be doing fine either way you go, but lift one up in the air and you won't have many options other than being able to engage a locker at that time.

My favorite thing about an LSD is that it's called a "limited slip diff", so it's not going to be able to control all of the slip. I heard once what the actual lbs/in it takes for a specific LSD (can't remember model) to slip, but it was quite lower than I expected.

 

[michaelgroves]

I'll add that with a 4x4, at least two of the 3 diffs (front center and rear) need to have locking ability for the lockers to perform. For instance, if your center and front diffs are open, with a locked rear diff, the possibility exists for one front wheel to spin, and thus lose all torque to the remaining wheels.

Very good point to remember - there's not much point to locking a rear axle unless you have the centre locked. All that will happen is that a wheelspin is more likely to be induced on a front wheel.

Even with front and rear lockers, and an open center diff, the possibility exists to lose all torque to either the front or rear wheels.

Actually, this is a very unlikely scenario. Only if both wheels lift off the ground completely, will there be zero torque (and then, of course, the other axle will also generate zero force). However, you are correct in that the total tractive force of the rear axle will be limited to what can be generated by the front axle (or vice versa, if the rear axle has less traction than the front).

I have an interesting scenario with my Land Rover Defender 6x6 conversion: Axle #1 (the front axle) and #2 are driven in permanent “4x4”, through a lockable centre diff. Axle #3 is selectably driven through Axle #2’s diff. All 3 axles are equipped with ARB air lockers.

With all locks (and 6x6) disengaged, the vehicle behaves much like a standard Defender with an unlocked centre – except that on extreme undulations, the weight of the rear is sometimes taken by Axle#3 alone , leaving the wheels on Axle #2 in the air. On the road, it’s the ideal mode.

With 6x6 engaged, and everything unlocked, the rear tandem always has more traction in total than the front axle, so it generally makes little sense to use that configuration – any loss of traction simply makes a front wheel spin. Locking the front axle diff helps, but at the cost of putting a lot of strain on the front halfshafts and CVs.

6x6 mode, with the centre locked works well – and in fact this is the mode to use whenever things become slippery, engaging or disengaging the 6x6 as needed, but leaving the centre locked.

We found we only needed the axle locks very occasionally, though perhaps more often than one might initially imagine with a 6x6. This is because with six wheels it’s possible to lift several wheel off the ground at the same time. (Regardless of the number of wheels on a truck, there are always three on the ground, one of which might lift off momentarily, leaving an absolute minimum of two in cantact with the ground. With 6 wheels, that means three or four wheels might be suspended, and if they are across different axles, then of course one needs axle locks).

But we digress!