Differential questions from a new guy

[daveb]

FWIW Sportsmobile suggested to install a selectable locker in the front as the primary locker. I understand what others say and I agree. Wheel spin can cause problems but I have yet to plop down the bucks for a rear locker. From experience I have been stuck in some situations where the front slips and walks off the trail sideways while the rear limited slip never gave way. My thought is that because these vans are so heavy the rear had no problems but the front did. Maybe I'm wrong but as soon as I engaged the front locker I moved up the trail with no problems at all. That being said turning is a big issue. There have been times that I've had to turn the front locker on and off several times during turns to get where I wanted to be. The limited slip has worked so well that a rear locker is low on my list at this time.

[Railvan]

"Stumpalump summed it up nicely. I agree!"

X2!

Front and rear air lockers here.

Brian Rutherford

[daveb]

Originally Posted by railbat

"Stumpalump summed it up nicely. I agree!"

X2!

Front and rear air lockers here.

Brian Rutherford

Yep, there is always that one climb you got to try . I usually run in 4x4 on steep loose grades even though I could make it in 2WD low. It makes sense to spread of the stress. I use the front locker only when it's needed. What I have to decide is what locker to purchase for the rear. As in the other post that is current, there are many opinions on which to choose. So far I have not been plauged with the leaking seal/lines problems that ARB owners have had. My biggest fear is getting into a place that almost requires at least one locker in operation, then having it fail. Sometimes it's rougher coming out than going in. This is where the extra traction might be a life saver. I don't do heavy rock climbing like some of you might because I have an EB, but my van is heavy and a rear locker would help. I feel if I have to use a front and rear locker to get into an area, I shouldn't be there in the first place. Not with a 11K EB van. I still would like the extra insurance.
Dave.

[warholic]

I have a comment - limited slip diff (LSD) is good when you are in 2 WD mode. If you need to be in 4WD mode, then the trannsfer case locks the differentials front and rear and they are in 4WD hi or lo, whatever you're in. The LSD isn't an issue climbing rocks or off-roading because you are in 4WD and the system works like any 4WD.

By adding front ARB, you give yourself more ability because you can lock the front axles so each tire gets 1/2 the power going to the front (1/4 of total power each). The rear is still acting like a regular 4WD without a locking diff - traction is split between the 2 rear tires altho the one that is spinning gets more of the torque. Tha's a different discussiuon, tho.

If you can afford an ARB in the back then do it because you get max 4WD capability, but LSD in 2 wheel drive mode is good because in normal street driving you get that extra traction LSD provides when one of the rear tires starts slipping for some reason.

So .... what's wrong with my thinking - technically or application- wise? Do I have it right?

[geoffff]

Originally Posted by warholic

then the trannsfer case locks the differentials front and rear

Front [to] rear... yes, that all makes sense to me.

The question I have now is -- does there exist a rear diff with both ARB locker and limited slip?

(I'm running front locker and rear limited slip. I do enjoy that limited slip for 2WD driving, especially when making a hard right turn and jumping out into traffic under heavy acceleration.)

-- Geoff

[jage]

Originally Posted by warholic

The LSD isn't an issue climbing rocks or off-roading because you are in 4WD and the system works like any 4WD.

This is the only part that seems off to me- in 4WD you've got the axles locked to each other, but without limited slip you're locking 2 open-diff axles (essentially 4WD means 2WD one on each axle).

Slight improvement gained by having a LSD in the rear, because now you've got 1 open and one LSD axle working for you... 2.25WD?) such as small difference can make a difference to getting stuck or not, depending on driver skill.

A locker then adds a whole WD to the equation so with a rear locker engaged and 4WD engaged it's actually 3WD. That's not to say that having the transfer case in 2wd and having the locker engaged (2WD) is equavilent to having the transfer case engaged and open diff axles (2WD) although I've met a number of people who believe a locker is nearly equavalent to 4wheel drive with open diffs. The gist is having pull in the front is more important than doubling the push in the rear (conditions dependant of course).

So ideally if you double your front (ARB locker) and have Limited Slip in the rear you're at 3.25WD on my little scale when everything is engaged and you keep the LSD for 2wd right turns in the rear. That sounds like a pretty good setup.

[Skywagon]

That's all true, but keep in mind that with limited slip, one rear wheel is not always slipping. So, if both rear tires have relatively equal traction, they're BOTH actually propelling you.
And, while locking both wheels on the same axle together will obviously give you the best traction, there are times when having no differential effect is a liability such as when turning on rocks where too much traction can make it difficult to maneuver. For these rigs, I like LS rear/ locking front. If I had a CJ-5 rock crawler, I'd want lockers on both ends.
Bill

[geoffff]

Originally Posted by Skywagon

That's all true, but keep in mind that with limited slip, one rear wheel is not always slipping. So, if both rear tires have relatively equal traction, they're BOTH actually propelling you.

And even when a wheel is slipping, with a LSD you're putting more power out to the wheel that still has traction than you do with an open diff. With an open diff, they both get the torque of the slipping wheel (perhaps almost zero), but with a limited slip, the good wheel gets that plus the torque required to slip the LSD's friction clutch plates.

-- Geoff