Could not find much in the manual or online on the subject. Any opinions on when the center diff should be locked or unlocked while in Crawl Control? I know it must be unlocked while using Turn Assist. But other than that, not clear when it is best to lock (or unlock) center diff in crawl as a function of what conditions. Thanks.
Crawl & Center Diff Lock/Unlock
- Thread starter Gss
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Taco2Cruiser
Crazy American Off Road
Without going into a thesis statement on off road traction and theory. In the basic of basics...
Lock up the center when you are:
1) climbing steep, mogul like terrain. Not really dirt tracks, but rocky, uphill situations where you put a lot of weight on the rear axle with little traction for all 4 wheels at the same time.
2) Mud boggs. Like sticky, muddy crap that requires wheel spin to get through.
3) You’re stuck. Everybody’s got to learn, it will eventually happen. Just try to learn from mistakes. But when it does, give the truck the best change and give at least the front and rear axles a 50/59 split. It will take a little work off the brake when in crawl. One day, you’ll remember the last time you got stuck was a coupe decades ago. But it will happen... at least once.
As you’ve noticed, all situations are when you need maximum traction, which also means you are limiting turning.
Like I said, this is the raw, simple basics, much could be added to this. But this is where to start.
Lock up the center when you are:
1) climbing steep, mogul like terrain. Not really dirt tracks, but rocky, uphill situations where you put a lot of weight on the rear axle with little traction for all 4 wheels at the same time.
2) Mud boggs. Like sticky, muddy crap that requires wheel spin to get through.
3) You’re stuck. Everybody’s got to learn, it will eventually happen. Just try to learn from mistakes. But when it does, give the truck the best change and give at least the front and rear axles a 50/59 split. It will take a little work off the brake when in crawl. One day, you’ll remember the last time you got stuck was a coupe decades ago. But it will happen... at least once.
As you’ve noticed, all situations are when you need maximum traction, which also means you are limiting turning.
Like I said, this is the raw, simple basics, much could be added to this. But this is where to start.
- Thread starter
- #3
Ok, thanks. Was not sure if use of center diff lock was the same when crawl is on or off. Understand the off case. Could not find anywhere if crawl mode voodoo somehow changed the regular “rules” for use of center diff.
Taco2Cruiser
Crazy American Off Road
The center locker doesn’t change anything as far as how CRAWL works.
But when a diff is open, you obviously don’t get a 50/50 power split. The power goes to path of least resistance, or away from the axle that has more weight on it, that will keep you moving forward better.
So CRAWL, limits the wheel with less resistance and try’s to send power to the wheel that has more resistance. So back to the locker, locking up the power to ensure that the front and rear get 50/50, the CRAWL only has to try and move power left and right on the same axle. Instead of to all four wheels, because the center locker is already ensuring that is distributed evenly, regardless of resistance on one axle.
Make sense?
But when a diff is open, you obviously don’t get a 50/50 power split. The power goes to path of least resistance, or away from the axle that has more weight on it, that will keep you moving forward better.
So CRAWL, limits the wheel with less resistance and try’s to send power to the wheel that has more resistance. So back to the locker, locking up the power to ensure that the front and rear get 50/50, the CRAWL only has to try and move power left and right on the same axle. Instead of to all four wheels, because the center locker is already ensuring that is distributed evenly, regardless of resistance on one axle.
Make sense?
- Thread starter
- #5
OK, I am following you. But seems like crawl operation would work better with the center diff unlocked. Meaning the voodoo could put even more than 50% power to either axle that has the traction as needed. So for example, if the front axle had no traction, the rear axle would get most of the power beyond 50% assuming a case where it had sufficient traction. This might be more of a burden on the brakes and center diff though.
Taco2Cruiser
Crazy American Off Road
Yeah I see where you are coming from. But remember that the brakes can not really hold back the entire engine power at a wheel. It can limit it, enough to help, but the brakes will always loose the battle with engine power.
Also, going back to my original 3 basics of when to use the center locker. All those examples are situations where you are needing maximum traction and forward power. Applying brakes is the last thing you would want to do when climbing a mountain or plowing through mud.
CRAWL has options for it, which is good for helping any driver with any experience. But CRAWL will never replace a locker, it is a great option for most of us, but sometimes, you just need to send power to the right place, in the first place.
Also, lockers don’t build heat, CRAWL does, a lot actually, and if you had the option to not burn up you’re brakes while on a steep mountain trail, wouldn’t you take it?
- Thread starter
- #7
Yea, that is a good point = while you may send all engine power to the rear in my example, the engine output may be cut if the rear brakes cannot handle full power. So not totally clear to me, but now seems like keeping the center locked in crawl may be best as full engine output is available over the two axles. With the exception of tight turning situations.
Taco2Cruiser
Crazy American Off Road
While I’m not telling you go out and get stuck. The only way to know the limits of your truck, is to find them.
The center in a 200 can’t send all engine power to one axle, in fact I don’t think can go below 30%? I normally don’t say “think” on the forum, but I’m on the move and can’t pull up documents quickly right now.
So unlike Land Rovers that can send almost all power to the front end while climbing (British engineering...) we will always have a much closer to 50/50 naturally.
When I first got my 200, I forgot to lock the center (only had part time 4wd before) and I hit a mud hole and done. Too much power went to the the rear and didn’t let the front lift up out of the hole, and then I pulled cable.
Until you are really getting it, I don’t know what your definition of hard wheeling is, but center unlocked will still take you pretty far.
Play with trying to climb rocks with and without he center locked to get a feel for it. But when I comes to mud, nah brother, lock it up.
- Thread starter
- #9
Thanks so much for the info. Interesting subject. Think I know what has been confusing me. Traded a Grand Cherokee in for the LC. It had their QuadraDrive 2 system which in earlier versions could shift full power to just one wheel if needed. The newer ones like I had did not do that but limited the amount to something like you suggest above for the LC. Also, interestingly, once you engage low range it automatically locks front and rear to 50/50. No center diff choice in the GC in low gear.
My brother has a GC trailhawk with Quadradrive II and the hemi. We drive off-road together offten, me in my LX570 and also with buddy in his heavy modded LC 80. The Jeep Locks the central diff in low range because otherwise the Clutch pack type central diff overheats quickly in situations where there is limited traction, a lot of speed differnace between the wheels. We found this out the first time he took it in the sand. He placed the traction dial in “sand” mode (and not 4low) and within 10 min the central diff overheated and shut the entire car down below the high tide line and I had to tow him to safety.
I can speak highly the difference in stock GC vs stock 200 in most off-road scenarios.
I can speak highly the difference in stock GC vs stock 200 in most off-road scenarios.
- Thread starter
- #11
Had the Trailhawk as well. Liked it but just did not seem like it would handle extreme pounding and always worried about the air ride reliability. It would go places but was dramatic as it has little suspension travel especially with the air ride Is raised. The Torsen in the LC by design is much more robust. Not sure how long it could go in sand without the center locked, but much much farther.
Imagine other than for traction purposes, the other reason to lock the LC center diff (in crawl or not, in low or not) is to relieve stress/heat on the diff. I think???
Imagine other than for traction purposes, the other reason to lock the LC center diff (in crawl or not, in low or not) is to relieve stress/heat on the diff. I think???
The LC center doesn't use clutch packs like the Quadra Drive II. I wouldn't worry about heat build up on it when unlocked, however minimizing extended ATRAC activation is a benefit.
His trailhawk is a 2013, been into the dealer 7 times for air suspension issues, they finally put an all new control module on it last year and it hasn’t failed since. It drives better on road but I agree is way too stiff off road and he almost never uses the highest setting.
For sand in my LX I don’t lock the diff, air down to 20 psi, turn off traction control, and use 4H unless I need to go very slow for technical sections then 4L. A few times a summer I do 20-30 miles on beach, dunes with soft sand with no issues
For sand in my LX I don’t lock the diff, air down to 20 psi, turn off traction control, and use 4H unless I need to go very slow for technical sections then 4L. A few times a summer I do 20-30 miles on beach, dunes with soft sand with no issues
