Center Diff Lock - Educate me please

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bmblum

Joined
Sep 28, 2005
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Location
Tempe, AZ
Can someone please point me to a detailed discussion of the CDL on a 2000 LC? Specifically, what exactly does engaging this button do? How does it compare to a traditional locker? When *should* one use this feature? When *can* one use this feature?

Brian
 
it's a full time 4WD. You can't have the front and rear shafts locked together on the road cuz there would be stress when you turn (they would like to spin at different speeds). To avoid that there is differential in the TC, so all is well onroad.

But offroad you could lose traction if one axle has a wheel that starts spinning. If so, then the center diff would cause you to lose torque on the other axle too. So you're stuck. Now if you lock the CD, then you would still send torque to the other axle. And off you go if you still got traction on the other axle. It's exactly the same idea as the diff lock in each punkin'... (if you're lucky enough to have them... :) )
 
As e9999 said w/ full-time 4WD that in some off-road cases all engine torque could either be sent forward or to the rear causing a stuck or tricky situation. Locking the CENTER diff means that torque is equally distributed between the front wheels and the rear wheels. Between left and right is your ``traditional locker''.
 
I tought it splits the power output to the front and rear diffs 50/50. With an unlocked center diff, the AMOUNT of power to the front and rear wheels can vary greatly, depending on driving conditions. This allows the front and rear tires to rotate at various speeds, particularly on turns to prevent binding in the driveline . When the center is locked, the power is evenly spread to both diffs, thus increasing the forward motion on very low traction surfaces.

The only downside to locking the center is that your driveline will " Bind up" on sharp turns when you are on HIGH traction surfaces such as pavement. It can be harder to turn , and can damage your diffs !

Only use the CDL on a slippery surface or in near-zero traction situations.
By that , I mean make sure you are OFF the Asphalt when you engage CDL.

I lock it regularly to disable the VSC in the dirt, Mainly so I have more HUMAN control over my 100`s power
 
Simple......With CDL unlocked you can spin any one wheel and be bogged. Lock the CDL and you have to spin one front and one rear at the same time before you are bogged!
 
I'm going to Winter Park to snowboard. We rent this house that is up the hills on snowpacked road. I think there is several inches of hard packed ice /snow.
Would locking the center diff be advisable when we start to climb up to the house?
From what i've read it sounds like the right way to go.
 
That depends on the year of 100 you have. For you (99) it will be needed more than a 2000+ with TRAC. TRAC can compensate some for the CDL but max traction is achieved with both working together. Once you're there, try it both ways so that you can get a feel for the 100. Do you have a LC or LX? Just wondering if you have rear locker or LSD?

For me, on icy roads, I like running without the CDL activated and let TRAC do it's thing. If it gets really nasty, you can lock CD and get even better traction. I have noticed that the TRAC doesn't kick on as much when the CD is locked. I guess that's due to the fact that the front and rear are pulling the same.

EDIT: One other thing, can you lock the CD on a 98-99 without locking the rear locker? Or is this something you have to change in the wiring? (Pin 7 mod maybe?)
 
Thanks, everyone, for your responses. Would it be correct to say that with the CDL locked power is distrubted like a tradidtional 4WD vehicle (such as my 1994 Toyota pickup)?

Brian
 
bmblum said:
Thanks, everyone, for your responses. Would it be correct to say that with the CDL locked power is distrubted like a tradidtional 4WD vehicle (such as my 1994 Toyota pickup)?

Brian
Click to expand...
Yes.
 
Greg B said:
Once you're there, try it both ways so that you can get a feel for the 100.
For me, on icy roads, I like running without the CDL activated and let TRAC do it's thing. If it gets really nasty, you can lock CD and get even better traction. I have noticed that the TRAC doesn't kick on as much when the CD is locked. I guess that's due to the fact that the front and rear are pulling the same.
Click to expand...

Greg: Might be OK on ice, but when 4-wheeling, on ANY type of dirt or rock climb, NOT LEAVE YOUR CDL UN-locked. If TRAC kicks in AND for some reason you need to BRAKE, the breaking does not kick in as TRAC has the priority. This same danger happens on non-CDL Rovers. You MUST lock your CDL, especially climbing and especially when flexed.
 
ShottsUZJ100 said:
Greg: Might be OK on ice, but when 4-wheeling, on ANY type of dirt or rock climb, NOT LEAVE YOUR CDL UN-locked. If TRAC kicks in AND for some reason you need to BRAKE, the breaking does not kick in as TRAC has the priority. This same danger happens on non-CDL Rovers. You MUST lock your CDL, especially climbing and especially when flexed.
Click to expand...

This logic doesn't make sense to me. TRAC can kick in whether the CD is locked or un-locked. If you are climbing something off-camber, of course you would want the CD locked for the additional traction it provides. Either way though, braking overrides the TRAC, it just takes a second to kick in.

I drove a LR Disco 2 for 4 years and it was the same way. ETC (LR version of TRAC) would kick in to keep you going, but if you had to hit the brakes, there was a delay before the ETC turned off and the brakes kicked in. The first two years I drove it without ever locking the CD since it was a 99 and didn't have the CD linkage. After those first two years, I added the linkage and liked it even more. With the CD locked, the ETC didn't kick on nearly as much. But when it did, the characteristics of ETC were no different in regards to braking.
 
Would like to add, from experience and from other's such, that when driving on any loose surface, like snow, ice, sand, gravel, you have more stability and less skidding during normal driving with the CD locked. More like driving on rails.
Another thing is when manouvering around sharp bends, when u might have more skidding, depending on how u use your feet.
 
Greg B said:
This logic doesn't make sense to me. TRAC can kick in whether the CD is locked or un-locked. If you are climbing something off-camber, of course you would want the CD locked for the additional traction it provides. Either way though, braking overrides the TRAC, it just takes a second to kick in.

I drove a LR Disco 2 for 4 years and it was the same way. ETC (LR version of TRAC) would kick in to keep you going, but if you had to hit the brakes, there was a delay before the ETC turned off and the brakes kicked in. The first two years I drove it without ever locking the CD since it was a 99 and didn't have the CD linkage. After those first two years, I added the linkage and liked it even more. With the CD locked, the ETC didn't kick on nearly as much. But when it did, the characteristics of ETC were no different in regards to braking.
Click to expand...

OK, here's a god source and link to others:
http://www.expeditionswest.com/vehicles/ewvehicles/Land_Rover_Discovery/cdl.htm
Pay close attention to #1
**********************
In my own experience, and when I've discovered I FORGOT to lock the CDL:

I've had 3 bad occurances:

2 we're average grade uphills with crossed ruts. Traction would suffer, TRAC would kick in, I'd be going nowhere, then I would start sliding backwards and sideways.....I'd hit the brake and the pedal would pulse for a COUPLE OF SECONDS then the brakes would work and TRAC would quit. BAD! DANGEROUS! SCARY! I lucked out!

1 was a semi flat area with a big washout and crossed terrain. Same thing happened, and AFTER hitting the brakes I continued to go backwards toward a closing truck. BAD!

This cannot and will not happen with the CDL locked.
 
ShottsUZJ100 said:
OK, here's a god source and link to others:
http://www.expeditionswest.com/vehicles/ewvehicles/Land_Rover_Discovery/cdl.htm
Pay close attention to #1
**********************
In my own experience, and when I've discovered I FORGOT to lock the CDL:

I've had 3 bad occurances:

2 we're average grade uphills with crossed ruts. Traction would suffer, TRAC would kick in, I'd be going nowhere, then I would start sliding backwards and sideways.....I'd hit the brake and the pedal would pulse for a COUPLE OF SECONDS then the brakes would work and TRAC would quit. BAD! DANGEROUS! SCARY! I lucked out!

1 was a semi flat area with a big washout and crossed terrain. Same thing happened, and AFTER hitting the brakes I continued to go backwards toward a closing truck. BAD!

This cannot and will not happen with the CDL locked.
Click to expand...

I apologize about sliding backwards on a hill climb. I'm with you on this one. It is definitely scary when that happens to you for the first time. On hill climbs of any type I definitely agree with you and Scott on locking the CD to eliminate this problem. That's one of the reasons I added the linkage to my Disco 2 a few years back.

I was disagreeing with your original blanket statement about locking the CD anytime you're on dirt. There have been many times that I didn't want the CD locked when off-roading on flat trails whether they were dirt, gravel, or rock. Why put the drivetrain in a bind on a flat trail when there isn't a need for the extra traction.
 
Looking for advice when travelling off road down hill on ice.....

I was on a back dirt trail which was covered with snow and ice and was descending a down hill section, the LC was in 4 wheel low and had my center diff locked.....

As I descended I started to get side slip I think this was caused in part by the locked Center Diff....any ideas or comments for next time?

fortunately I kept it on the trail...
 
Big Bert said:
Looking for advice when travelling off road down hill on ice.....

I was on a back dirt trail which was covered with snow and ice and was descending a down hill section, the LC was in 4 wheel low and had my center diff locked.....

As I descended I started to get side slip I think this was caused in part by the locked Center Diff....any ideas or comments for next time?

fortunately I kept it on the trail...
Click to expand...

I never run CDL locked when on snow or ice. If I get into a spot where I lose traction I'll then lock the CDL and unlock ASAP. (Just like using a locker)
 
Winter Driving in the Winter Country...

When driving on snow or ice, it's always better to have the CDL on, EXCEPT when manouvering with sharp turns when you don't need the extra possibility for traction. It gives you more stability, easier to keep the track, and easier to use the brakes in a controlled way. It's better even when you have ABS because there will be less work to do for the ABS.
Then, when going downhill, if you stay in a low gear, the braking force of the engine will most probably be too high, resulting in lack of grip and skidding/slipping. This is of course dependent on road/track conditions and the angle of descent. When you loose traction this way, it means that you do not have enough grip to reduce your speed down the hill, or even to keep the current speed. The best thing to do is to NOT use a low gear, and instead use the brakes (with ABS). That way you will have enough grip to steer at the same time. And praying that the hill is not too long, or as slippery all the way, or doesn't get steeeeeeeeepeeeeeeeeeeeeerrrrrrrrrrrrrrrrrrr....
So, Big Bert, next time: CDL on, Hi range, D(rive), if it's that slippery.
Otherwise, if not slippery, normal rules apply, i.e. low gear down hill.

Good luck
 
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