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Discussion on Axle Traction Devices and 'Lockers'

Moses Ludel's installation of an ARB Air Locker in the XJ Cherokee 8.25

Here, I install an ARB Air Locker at the rear axle of the '99 XJ Cherokee. This is my traction device of choice for this application.

     Note: Keith Martin is the publisher of Sports Car Market Magazine and a personal friend. We were colleagues and each wrote for the Portland Oregonian newspaper in the 1990s. Keith has an affinity for British Land Rovers and recently found his prize: a 1989 Land Rover 'Classic'. Planning to upgrade the axle traction system, Keith wanted my viewpoint. Enthusiasts will find the comments applicable to Jeep 4WD vehicles.—Moses Ludel

From: Keith Martin
Sent: Saturday, January 29, 2011 11:17 PM
To: 'Moses Ludel'
Subject: Range Rover Classic Locker question

Moses, I drove the '89 RRC on its first snow run today. After airing-down to 15 lbs, the rig was absolutely brilliant. Just walked past all the Series Rigs and kept up with all the big dogs of the club. That, with two teenagers and a toddler in the back, and after driving 225 miles up from Portland to Sultan the night before. This is great fun.

What is your opinion on lockers? The Internet forums say Detroit Soft Locker in the back, TrueTrac locker in the front. The Rover boys say anything besides an ARB hard locker is a compromise. Shipman says that he never recommends lockers for the front as they overstress the axles and spherical couplings up there. Your opinion?

Mine is that we are dealing with really low-stress situations here (the girls will mostly drive this rig off road, as I will be in the Series) and I’m looking for a cost-effective solution to an occasional problem. And I’m not sure the milliseconds between engagement of soft lockers versus hard lockers will really make any difference.

Any thoughts here? Thanks.

KM

From: Moses Ludel
Sent: Sunday, January 30, 2011 8:44 AM
To: 'Keith Martin'
Subject: RE: Range Rover Classic Locker question

Keith, I recommend an ARB Air Locker at the rear. You can always add a front ARB later if you desire. I am a strong advocate of manual lockers.  Automatic lockers, soft or otherwise, are a hazard on off-camber, icy highways. Spinning both wheels at an axle can drop the vehicle to the low side of the road or cause a complete spin-out. The same situation occurs off-pavement on an off-camber slippery surface like mud or snow. Locked at both ends, a 4x4 can slide sideways off a slope.

I use ARBs, front and rear. My driving habits take front joint stress into account. I will often run the front axle open, the rear locked, gaining 
traction but not compromising steering angles or stressing steering joints and front axle shaft joints.

Try a manual ARB Air Locker at the rear. You’re in control. On an icy or slippery off-camber surface, I recommend running the axle “open”, not locked. Lock when you need the added traction off-pavement. The rear axle locked makes a huge traction difference and eliminates most front wheel spin as well.

Glad you’re enjoying the ’89 RRC!

Best,

Moses

Reply from Keith Martin:

Getting back to the Detroit, for the kind of casual use we have in mind, would it really make any difference if you didn’t have control? Do you mean if I had soft lockers front and rear and were on an icy, off-camber road they might lock up of their own accord and slide me off the road?

KM

Moses' response:

Yes, I really do mean this, Keith…I do not use automatic lockers. Our Dodge Ram has factory rear limited slip, and I am cautious on icy, off-camber highways. Both wheels spinning at the same time on an off-camber road is anathema. A Detroit with a shorter wheelbase can also cause “torque steer” when getting on and off the throttle during turns on asphalt…I’m surprised the Landie/Rover ‘wheelers do not discuss this…ARB has been very popular, a virtual standard, for Land Rover applications…Moses

From: Keith Martin Sent: Sunday, January 30, 2011 9:04 AM
To: 'Moses Ludel'
Subject: RE: Range Rover Classic Locker question

Moses, thank you for your (as-always) prompt and informative response. The ARB is much more expensive than a soft locker, hence my question. Yesterday, we were in deep snow, my final stopping point was the frame bottoming out on the snow. So I understand nothing but a lift kit would make a difference there, and another 1.5” might have gotten me another 50 feet!

With my '88 model, Shipman has advised me against using the locker in the snow, but it seemed like yesterday it would have made a big difference.  

Okay, last query. My last three Suburbans have had soft lockers in the rear, and have always been docile and predictable.

This is the same system we are talking about here?

KM

From: Moses Ludel                                                                      Sent: Sunday, January 30, 2011 4:59 PM
To: 'Keith Martin'
Subject: RE: Range Rover Classic Locker question

Keith…Your last three Suburbans had long wheelbases in the 131” range. A long wheelbase vehicle with a G.M. governor locker or similar automatic locker is softer; at that wheelbase, the vehicle is less torque steer sensitive. We had a 1986 Suburban ¾-ton and tested a traditional Detroit “hard locker”. The test lasted less than two days. Aside from the annoying ratcheting (hard locker characteristic) on turns, the vehicle’s handling on pavement was noticeably different—in a negative way. 

We used a Lock-Right prototype in one of the Geo Trackers that I took over the Rubicon Trail in 1995 as a publicity stunt for G.M. It worked great off-pavement at crawl speeds. On the pavement with that extremely short wheelbase, the Lock-Right would chirp tires when making a U-turn. The vehicle torque steered dramatically on the highway, every curve in the road a handful. 

I did install a Detroit TruTrac (helical gear design, click here for details at the Eaton website) in the rear axle of the ’55 CJ-5. It works okay in terms of minimizing torque steer on the pavement. Other than the off-camber icy highway risks under acceleration, this design has merit. I still prefer manual locking, the ARB Air Locker or similar types.

I suggest you drive one of the Rovers equipment with a Detroit soft locker. Test it for torque steer on asphalt corners. If possible, drive it on the road to Mount Hood on ice—carefully.

The Wrangler Rubicon rear axle does use a helical-gear type diff, more like a TruTrac, when the axle is unlocked. Locked, this axle is like an ARB or Ox manual locker. The Rubicon's front axle is a manual locker with no automatic locker provision. It is an open differential when unlocked.

The helical gear automatic locker is a less obtrusive design like our Dodge Ram 3500 uses…Here’s another possible vote for the Eaton TruTrac. In any case, drive it gently on that icy, off-camber highway!  I prefer an open diff and the manual locker for better directional stability under those conditions. I run unlocked on icy highways in 4WD mode.

Off-pavement, the time-honored, trail runner (trailer queen) paradigm for a short wheelbase Jeep has been a Detroit Locker at the rear and a factory-type Trac-Lok multi-plate “automatic” limited slip at the front.  Backing off the throttle makes steering possible. Again, in my view, the failsafe means for all around vehicle use and controlled handling is the ARB Air Locker or other manual lockers. Locked, you get pure, instant 50/50 torque split to each wheel of the axle. Unlocked, you have a conventional differential. 

Here’s a forum exchange I snagged in two seconds: click here. Read Desert Dog’s comments…They mirror my experience. Note his reference to the Suburban and TJ Wrangler use of a Detroit Locker. The Eaton E-Locker is a driver-controlled (electro-magnetic) manual locker.

When I drive on loose, off-pavement surfaces, I often lock the rear (ARB) axle and leave it locked. At a 101.4" wheelbase, the XJ Cherokee handles well in this mode on dirt. When I need rockcrawling traction on a relatively straight pull or with one wheel in the air, I lock the front axle. This is off-pavement gain to the maximum. In the winter, on an icy, off-camber highway, I’m grateful for 4WD with open diffs at the front and rear of the vehicle for directional stability.

My take…Moses

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