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I am new to this site, and new to Discovery's. I recently purchased a 1998 LSE from Nashville, TN. I am unfamiliar with the 4 wheel drive system and would like some input. I understand that the Discovery is supposed to have full-time 4x4. During a recent snow storm, I tromped on the gas and only the front wheels spun. Then, I locked the differential, and the back tires as well as the front spun. My question, should my back tires have spun when the differential was unlocked? It was like I have a front wheel drive SUV. During the same snow storm, I tried to pull a Chevy van out. I locked the differential in high range. All 4 wheels did not spin. When I locked it in low range, all 4 wheels grabbed and I could pull the van anywhere. Am I having issues with the transfer case, or are the above scenerios normal? :drive:
 

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There are no true 4wheel drive vehicles sold on the market. In the case of your Disco, you have power to the left front and the right rear. When you lock you t/case with the CDL it only splits the power 50/50 front and rear for a little better traction.
To have all 4 wheels have full power you would need to have installed what are refered to as locking diffs., one in the front housing and one in the rear. Then when you are in a slippery situation all four tires turn with equal power.
With you truck, you may see the power slip from the left to the right wheel if your are powering thru some slippery snow, but it is limited.
Hope you enjoy your new truck and stay in touch with us with any questions.
Mike J.
 

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Discussion Starter · #3 ·
Thanks for the response. One argument I would like to have is about the true 4 wheel drive cars, and that there aren't any. My wife has a Ford Expedition and it has true 4x4. I pulled someone out a couple years ago in deep sand on the Outer Banks and all 4 tires dug nice deep holes before the Jeep came out of the hole it dug itself. It was a high torque situation, and all 4 tires were turning together. I was impressed.
 

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So will the disco (spin all four if all four have equal traction), but if you had one side on ice and the other on pavement you will find that the 2 on ice will spin and not the two in pavement. To spin all four with different traction you would need diff-locks added (or an H1 with the torsion diffs or optional detroit lockers).

Be impressed anyway, not many are impressed with exploders.
 

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The Expedition probably has limited slip which will spread the traction around some but not evenly, just as the newer Discos with electronic traction control, but it is not spread equally to all wheels.
Only lockers can spread it equally.

Parthog, Discos don't spread it equally, if they have ETC the pass the power from front to rear and from left to right by the ABS restricting the spin on a spinning wheel. It works, and depending on the ABS sensors you may only have traction on one wheel.
Mike J.
 

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I guess you're thinking D2, I'm thinking D1 with three open diffs. With the 3 open diffs (which is the original truck in this discussion I believe? a '95?), you would (in theory) have 25% torque evenly split between the four wheels regardless of traction. Lift one wheel, you have no drive. With the CDL, you have up to 100% on either axle, but split 50/50 between the wheels on that axle (which would happen if you were for example climbing with one front wheel lifted, the rear axle would get all of the torque from the locked center diff).

And unless I'm wrong (haven't bought a new Ford in a while), a limited-slip rear differential was (is?) offered on the rear of the explorer, none available on the front.
 

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Parthog,
You may want to do some reading on diffs, both open and locked. Open is just that, power usually in the case of a Rover goes to the left front and the right rear and can spin over to the other side only fractionally. If you have a limited slip type diff, you can get a little more power, and it is limited based on how good the clutch pack is, to the non-slippinhg wheel on a diff. Only if you have a true locker, like an ARB or a Detroit do you always have equal and totaly locked wheels. That is why if you are big into rock climbing, like I am, you have to have true lockers, anything less is just slipping and spinning from one wheel to another.
CDL's are designed only to lock and split the total power from the t/case equally to the front and rear ring and pinion, what happens from there is determined by wether you are locked, limited, open and to some extent, ETC on some vehicles.
Mike J.
 

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The center diff lock or CDL locks the output shaft rotational speed together. I too have a locking rear diff, have not yet been able to justify a locking front diff. When I grow up I'll buy more goodies. My H1 had the torsen differentials like the quattro genII system, step on the brake and you're locked.

I don't know if you're just getting lost in the terminology, but yes the open diffs in the D1 allow all four wheels the same amount of torque, regardless of their traction. In such a case, if you were rock crawling in a D1 with diffs open and lifted one front wheel, regardless of which side, it would spin and you would no longer have any power to move forward. Ditto if you were backing up the same rock and lifted one rear wheel: regardless of which one lifted you would spin it and no longer be able to climb. This system is excellent for on-road, keeps tire and drivetrain wear down and improves handling. It is not the best for off-road which is why the CDL was standard on the D1s (pre-traction control).

If you were to hook a tow strap to a heavy load, leave the diffs open/unlocked, sitting on level ground with same traction on all four wheels you will likely spin both front or both rear wheels (depending on weight distribution or whether the strap is going uphill or downhill, etc.). If you lock the center diff and try again, you will likely spin all four wheels.

The center diff lock, or CDL, will cause the other axle to still be driven. In the first scenerio, the rear wheels would continue to drive you up the rock even with one front wheel lifted.

Not to get into a pissing match, as it wasn't what the original post was about, but open differentials such as in the Discovery do not favor a right or rear wheel. I've never seen a modern automotive differential that favors one side, that would eliminate the purpose of the differential (to drive two wheels with equal torque regardless of relative speed). If you are high on the LR and RR, the opposite wheels will spin. If you are high on the RF and LR, the opposite wheels will spin. Try with open diffs, you will find out that either front wheel in the air will stop you. Remember we're talking D1 here, no traction control.

I used to laugh when people would tell me that their RWD musclecar's right wheel was the "power wheel" because it was the one to spin in a holeshot. No, the open differential sent the same torque to both rear axles, but due to the clockwise rotation of the driveshaft it would lift the right side slightly during hard acceleration and therefore that tire would be the first to spin.

The exploder in the original comparison likely had the standard part-time 4WD system, no center differential, so it had to spin at least one front and one rear wheel. One would have to assume that the Discovery 1 would have performed the same with the CDL engaged in the same situation: spin all four wheels. It is possible, however unllikely, that the Explorer had a limited-slip rear diff but from my experience those are unusual from the factory.
 
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