It's taken many, many years of marketing but contrary to what most people think about their vehicles the fact is most factory 4WD vehicles actually are not truly 4WD. Now some manufactures offer locking differentials as options on a few vehicles (Wrangler Rubicon for example) but the vast majority of 4WD and 'All Wheel Drive' vehicles are actually not.

To further confuse the matter many new vehicles have traction control that can activate the brake on the wheel without traction and thereby direct power to the wheel with traction. Even though these are 'open' differentials they act like a locker or at least like a good limited-slip. Now I bet you're really confused! ;-)

 

For comparison, both the Toyota Land Cruiser FJ80 and our Rovers are full time 4WD. This requires a center differential to allow the front and rear axles to spin at different speeds. The FJ80 uses a viscous limited slip differential, delivering up to 30% of the power to the front wheels automatically. The FJ80 center diff is lockable in high and automatically locked in low. Our rovers use a normal open diff, just like the front and rears, except it's lockable like an air-locker, but actuated with mechanical linkage instead of air. We control the locking of it both in high and low. One nice optional feature of the FJ80s is electronic locking front and rear diffs. For our Rovers, if we want front or rear lockers, we have to add either air-lockers, TrueTrac, or Detroits.

 

It is said the original suspension design was prompted from the 1966 Bronco. If you learn to drive a Disco with functioning 4 wheel ABS you pretty much can do as much or more than some with lockers & limited slip. By applying brakes when one or more wheel(s) start loosing traction, the ABS will apply brakes to spinning wheel(s). It takes a bit to get used to this concept, but it works. Lockers are a killer in slippery snow & ice conditions, the vehicle only wants to go straight. Try driving a slippery snowy side hill & you are guaranteeing a slide to the bottom. Most NA trucks only have 3 channel ABS-2 at front and one for rear axle.

 

Here is how a full time 4x4 works, front diff is open, meaning both wheels are NOT locked together and they both get power under normal driving BUT when one wheel looses traction all power that is being sent to that axle will go to the path of least resistance.
The rear axle works the exact same way as it is also open.
This type of differential allows you to turn corners without increasing tire or driveline component wear and it also allows for tighter turning because each wheel can turn at a different speed.
The center differential (transfer case) is the exact same way only it allows each drive shaft to turn at different speeds and it sends power to the path of least resistance.
So if both rear wheels are on ice and both front wheels are on dry ground all power will be send to the rear driveshaft, because it is the path of least resistance.
Lock the CDL (center differential lock) and now both drive shafts are locked together and will turn at the same speed no matter what.
So if the rear wheels are on ice and the fronts on dry ground you can now move were as before you would have just spun the rear wheels and not moved.

A all wheel drive system uses clutches to transfer power front and rear as well as clutches in the differentials to send power left and right.
Thats what a Subaru does, clutches.

A Land Rover is all gears, no clutches, no viscous couplers, just plain old gears, heavy solid gears bolted into a heavy solid axle which is bolted to a heavy solid boxed ladder frame that is strong enough to build a bridge out of.

Jeeps may have solid axles but they have unibody frames and chain driven transfer cases.

Here is how a differential works, and a Land Rover has three, front, center and rear.

https://landroverforums.com/forum/di...l-works-40804/

And you cant do this with a unibody frame.

Land Rover Discovery / LR3 The Big Lift - YouTube

 

Hey Spike,

Thanks for the explanation. I get what a differential does. I think I was just under the mistaken impression that a CDL in a Disco would lock everything together so that if one wheel got airborne, the wheel on the opposite side would still get power. Instead it just locks the front and rear driveshafts together at the transfer case, correct? So in this way its similar to a Jeep.

Sorry for the simplistic questions. I've been doing a lot of research the last few months on Jeeps and only recently have begun to look at Discos. A lot of stuff on them seems to be very similar with different phrasing (and lots of stuff is different, like the Jeep's unibody design Spike mentioned above.)

Thanks for your patience, everyone.

 

I currently own a jeep (CJ-7), early Bronco and the D1. I've had several jeeps, this is my first LR. The LR is stout and actually fairly easy to work on. It's great in the snow and has lots of 'modern' niceties that make it a good daily driver (aside from gas-mileage).The parts are a killer though. LR parts (at least in my neck of the woods) are hard to get (none in the salvage yard) and they can take a while to get here. I can go to Napa and get nearly anything for the jeep though quickly and inexpensively.

As with everything, your intended use will dictate which direction you go. If you want open-top wheeling and ride/storage/hauling aren't as important to you the jeep (CJ series) is hard to beat. However if you need heat/AC, seating for seven, AWD and a relatively cheap buy-in, the LR is hard to beat.

I would guess you are looking at Cherokee's if you are also looking at the D1. In that case the LR is much more for all the reasons stated by Spike above. However the jeep has a huge aftermarket following and again the parts are cheap and easy to find.

 

I have never had to buy or price Jeep parts, but I think DI parts are cheap enough if you know where to look.
If you plan ahead you can order the parts and have them on hand before they are needed.
If you live in a well populated area, like say the east or west coast, parts can be had in a day maybe two.
If you live in the middle of the country and the nearest town is 60 miles away, well, then buy a Jeep or a Chevy and make do.

 

I'm actually surprised to hear that Discos are easy to work on. I always assumed their internals were some ultra-British Rube Goldberg-esque contraption.

 

I did a quick comparison between some brake parts for a 94 Cherokee and a 94 D1. First, Napa doesn't list any specific parts for the D1 on their website. From my experience trying to get specific parts for the LR at Napa, their Rover pricing is completely ridiculous. So I used AB for D1 pricing, Napa for jeep parts.

Land Rover:
ABS ECU: $1049
ABS sensor: $329
Brake caliper: $147
Master Cylinder: $234

Jeep Cherokee:

ABS module: $126
ABS sensor: $179
Caliper: $25 (loaded)
Master cylinder: $73

KBB value on 94 LR in good condition with 100K: $1439
KBB value on 94 Jeep Cherokee in good condition with 100K: $2298

Please don't read this as an endorsement of the jeep. The LR is far superior in design and out of the box capability and with the lower buy-in you can afford to pay a bit more for parts.

Perhaps there are better places to shop than AB but I still have to pay shipping on all my LR parts and Napa has most jeep parts in stock or from another store with no shipping.

OK, bring on the flames. ;-)

 

Thanks for the info. That's good to know. Could I get your advice in this thread, too?