Front Axle Traction?

[Eagle]

Recent snow followed by icy rain has gotten me thinking about traction again. Since I drive my XJs and MJs primarily on the street, I find a rear limited slip to be more than adequate for my needs. However, other than my brief sojourn with the ill-fated 1999 Grand Cherokee, I've never had any front traction devices.

 

About the only good aspect to that '99 WJ was the Quadra-Drive system. And not even the whole thing. The transfer case had problems, but the gerotor axle devices worked great. Which has always left me wondering why people aren't using that in the front axles of XJ and MJs.

 

For those not familiar with the original Quadra-Drive system, the axles worked kind of like the opposite of a Trac-Lok. With Trac-Lok, the clutches are engaged, until there's enough difference in torque on the two wheels to make the clutches slip (such as going around a corner on dry pavement). With the Quadra-Drive axles, the clutches are normally NOT engaged. There's a mechanical/hydraulic pump mechanism built into the differential. When one wheel starts to spin faster than the opposite wheel, this causes the pump to start pushing the clutches together, generating increasing lockup.

 

Ignoring the brakes and hubs at the outer ends, is the dana 35 differential used in the '99 and '00 WJs any different from the XJ and MJ Dana 35s? Is there any reason why an MJ front axle couldn't be set up with one of these gerotor traction devices?

 

Does anyone know if these things are available through aftermarket channels?

[yxmj]

I don't want to miss inform but I believe it goes like this.....I looked in to this myself a while back....

 

The "gerotor traction device" was located in the transfer case.(NP249)

 

The diffes that were used were called "Vari-LOK"

 

Here is some reading material that might get you on the right path

 

http://www.naxja.org/forum/showthread.php?t=14443

 

http://www.jeepsunlimited.com/forums/showthread.php?534750-Vari-Lok-Hydra-Lok-differentials-questions

[Blue88Comanche]

I also looked at this in the past.  I liked the idea, but i think i read that the D30 housing was slightly different for the pump....
 

Well, not much to say that hasn't been said. The lockers are called Vari-loc by Jeep, Hydra-loc by the units original manufacturer. There is a clutch, piston and oil pump inside the case. When one axle spins faster than the other, the pump produces pressure that applies pump pressure to the piston and then apllies the clutch and locks the diff. Very similar to a trac-loc with the clutches, but will release and not cause steering drag. This unit will not totally lock up, but is better than an open differential. The D30 in the front of the WJ's is slightly different than the average XJ D30, it is machined to accept the oil pick-up plenum that is attached to the ring gear side of the carrier. The axle size is larger, not sure about the spline count though. Custom axles would be needed to run this unit.

[Eagle]

I don't want to miss inform but I believe it goes like this.....I looked in to this myself a while back....

 

The "gerotor traction device" was located in the transfer case.(NP249)

 

The diffes that were used were called "Vari-LOK"

 

Here is some reading material that might get you on the right path

 

http://www.naxja.org/forum/showthread.php?t=14443

 

http://www.jeepsunlimited.com/forums/showthread.php?534750-Vari-Lok-Hydra-Lok-differentials-questions

 

You are correct that the axle devices were called Vari-Lok, but they (as well as the transfer case) were operated by a gerotor pump.

 

Hmmm ... I wasn't aware that the Vari-Lok axles used different shafts. That could be a deal-breaker right there. Might have to reconsider the old tried-n-true lunchbox locker, or TrueTrac.

[Jeep Driver]

Both of my difs are open. I want a locker for the rear as I'm tired of wheel spin where 4W isn't necessary.

 

I also drive primarily on roads, lots of steep gravel drives.

 

Our road to our housed is iced, has been for a couple of days now. I have no problem going uphill on icy roads even with open axles.

[mvusse]

I would not get a lunch box locker in a front axle that gets driven on the street in 4wd.

 

Limited slip or selectable locker only.

[Eagle]

I would not get a lunch box locker in a front axle that gets driven on the street in 4wd.

 

Limited slip or selectable locker only.

 

Common misconception.

 

Front axle OR rear axle, once both wheels on the same axle are on slippery stuff, there is no difference between a limited slip and a locker. There isn't enough traction for either wheel to overcome the clutches in a limited slip, so it performs exactly the same as a locker.

 

I've been doing this for fifty years, I have a better than basic understanding of how it works.

[mvusse]

No personal experience with limited slip. Lot of personal experience with automatic lockers. Front axle locked on ice or packed snow = going straight no matter which way you point the front wheels.

 

Actually, to be honest it's not that predictable. Some times it does turn, most of the times it does not, can never tell beforehand if it will or not.