I have an automotive question for those who may be stopping by today who do serious off-roading:
I understand the idea and theory of locking differentials.
I could, most likely with the tools I have, install them.
However, I’m not sure that I need them.
My experience on non-paved surfaces in limited to things such as this
 This being probably the most difficult.
I’m not going to go rock climbing, or out to the dunes, or even so far as in the above pic with Grimm.
Most of the trails I’d be travelling would currently require mucho pavement time to even get there, so the majority of the miles will be on asphalt.
So my question is, are they truly worth the investment?
The same goes for aftermarket hubs. The truck has made it since 1977 with the factory parts so, is it worth the invesment in say Mile Markers or Warn?
I started getting into offroading a short while ago so I will not be your most informed commenter.
I think a limited slip diff. (for the rear) is the absolute minimum for a bug-out vehicle. Knowing that lockers multiply traction, I guess it comes down to prioritys.
Some opinions on locking hubs are, full time hubs are stronger (fewer moving parts) but selectable hubs may keep you going if you break an axel.
Shoot straight, Jim.
I live, work, and play in hilly terrain. My experience is that limited slip in the rear axle is very desirable in that it allows you to subject the drive train to assymeteric loads without losing power to the ground. For example, when crossing a ditch on the diagonal the load on one wheel of each axle may be decreased to the point that they spin and there you sit.
Keep em’ in the 10 ring.
Cowboy
I’ve crossed plenty of ditches on the diagonal in a military issue HMMVW, and they don’t have locking differentials.
Lockers just help you get MORE stuck, in my honest opinion. For a bugout truck your destination is probably one that can already be reached via a normal vehicle, so you shouldn’t have to worry too much about offroading. However if you do have to bypass a traffic snarl and get stuck in a mudpit, using a couple stakes in the ground and a winch will get you out a lot quicker than lockers will.
And if you need to climb a real steep hill, once again the winch will get you up there and the lockers won’t.
Just something to think about.
Jimro
I’ve been driving Jeep 4WD vehicles since I’ve been driving, so these experiences are limited to that brand. My first Jeep was a ’54 Willy Wagon, and the last one I have driven off road was a 1999 Jeep Cherokee.
The best difficult-terrain climb I ever saw was in a ’42 Military, strictly stock, with 5 hunters aboard, climbing a 30% shale slope with a 40-50% rock lip at the summit. The driver just cruised up in low range second gear.
I then attempted the same slope in a ’65 CJ5, Powered by a Buick Skylark 231-inch aluminum V-6, with semi-locking rear. I used low-low, as the vehicle was geared wrong (too high) for higher gears. We only had about 300# of load. I almost didn’t make it, as the vehicle lost traction just below the lip when the rear diff dug the tires into the shale scree. The scree was less than a foot deep, and the extra clearance of larger tires let me get a grip on the substrate rock and over the top I went with a lurch.
I’ve been in very deep mud that the semi-locking rear diff didn’t help, either, and blew a tranny once when the semi-locking went locked at max torque and the tranny was the weak point and I lost a tooth on the main gear, which caused the gears to separate and split the case. I didn’t close the throttle soon enough and stripped out the primary gear line in the box. The mechanic who replaced it told me that it wouldn’t have happened with a standard diff.
The front hubs are probably OK, I’ve never known or even heard of anyone breaking one on a Ford. They DO need to be very well lubed to work as advertized, and even the vaunted Warn used to have problems of having to rock the vehicle back and forth to engage the hubs, very annoying.
I hope that Grimm is not equipped with a full-time 4WD system, which were just becoming popular in those days, especially in the Jeep Eagle. The Sprague unit in the front driveline was supposed to unlock the outside wheel in a turn, thereby alowing you to cruise through a turn in 4WD without breaking traction (with the outside front wheel unlocked), but in fact they frequently locked, then unlocked in turns, and if you were at the limit of adhesion, could easily spin the vehicle out when they cycled. Eagles were famous for swapping ends in Fulltime 4WD, and the Sprague was the reason.
My 46 years of driving Jeeps has taught me to use 4WD ONLY when stuck off-road, or pulling a hill in snow/ice while ON the road. In the older vehicles, shifting in and out of 4WD could be problematic if you waited too long, but such problems pale in comparison to troubles of trying to drive all four on the hard surface.
By the way, the paletary-gear drive setup on the military HumVees was a bad design, and if they ever hit the surplus, don’t plan on buying one. The plantet-drive units had a mean time between failure of 28 hours when first introduced back in the 80’s. They have been improved since then, but it is still a far-inferior system to a differential. It’s only advantage is that it gave higher ground clearance with lower vehicle profile.
My knowlege is very limited, but here’s what I do know and where it comes from:
Locked diff on a street vehicle = very bad if you ever plan on turning corners. Most useful for drag-strip cars.
FWD – I’ve owned a ’91 Mazda 4×4 pickup, and a 2002 Chevy Silverado 4×4 pickup. Both with strictly factory drivelines, and to be honest, I don’t know a lot more about 4×4 than that. What I do know, is that neither of them liked turning on dry pavement in 4WD. AT ALL. Drivetrain gets into a bind, and I start getting wheelhop even at low speeds.
With 4WD engaged, on both trucks, all 4 wheels seemed to be locked together. The Mazda would actually stop BETTER on wet roads in 4WD, because no one wheel would lock up unless all four did, and it’s rear ABS was pathetic. The Chevy’s better at stopping in wet, but still lots more stable in the rain with 4WD engaged.
I haven’t done a LOT of offroading, but I have been in some mud with both trucks, and didn’t have a problem with the stock 4WD drivetrains. I don’t see where locked diffs would have really gained me anything, and probably would have just created more problems, from minor like increased tire wear, to major like broken drivetrain parts, on pavement.
If Grimm’s destinations include places where no less than three tires can keep decent traction, I’d stay with the stock setup, and just make sure everything’s in good working order. Maybe do some research and find out what the weak links in his drivetrain are and beef them with stronger aftermarket parts, but keep the overall function stock.
Just my $.02 – whatever that’s worth these days.
Unless you’re purely rock-crawling for publication in 4WD Magazine, then you don’t really need a locking differential.
Limited slip is for the most part, a good thing.
At present, the GMC/Chevy trucks offer locking diffs, as opposed to a limited slip. Though this works damned well on a slippery boat ramp, I don’t like it for much else.
I do feel for the poor GM owner who has his diff lock up (it is electronic-sensor controlled), and then snap, when driving on pavement with intermittent ice or snow.
Your old Ford is adequate to the task, just as it is. The “X-treme” mudders and rock climbers are not representative of the needs of a true bug-out artist, who will use the vehicle as a tool, and not just a ego gratifying weekend entertainment device.
You wouldn’t use an M-1a with fixed bayonet as a your axe. You also won’t use your bug-out Ford to entertain yourself on the Rubicon.
Keep it in perspective, and put that money saved into ammo supplies.
Jim
Sloop New Dawn
Galveston, TX
Thanks everybody, that was the opinion I was getting as well.
Comment about Jimro and the HMMWV. It does not have a locking Diff, but instead used the brakes on individual wheels to prevent adverse wheel spin, so in effect similar , and yet different (and more effective) way to get power to the wheels that need it.
As to the locking diff, it is a boon if you have a RWD vehicle and you need to do some off roading. Cheaper to use and maintain than 4WD. I have a RWD 99 Jeep Cherokee, that has passed many 4WD’s on the trail. If I had a locker I would be able to do a little more. But if I did have a locker and/or 4WD I would never engage it until it was needed, as in stuck. And the best recovery you can have is a hitch mounted winch. That way you can take it off when you do not need it, will not interfere with your clearances and angles, and can mount it fromt or rear for the best usage.