4WD

[Ang1Sgt]

I’d like to add one thing here. Get used to slipping into 4WD when you can. FEEL how it engages so you know it has engaged. Do it on nice flat level ground going straight. Then shift it back into 2WD and ensure it disengages well too. Much better to do this before you have to on a snowy day or a situation that you need 4WD.

Also, my personal thoughts is that you should engage it at least once a month so you are working everything in the vehicle. Gosh the number of times I’ve worked on cars with set up hand brakes because they NEVER EVER used them except the one time they parked on a hill and they would not release….

There are times I really wish I had Select-Trac in mine. I really loved that in my 2003 WJ that we took everywhere! If it got nasty out with Snow and Ice, pop het into 4WD Auto. If it was still really slick, drop it another into the 4WD High where it locks both front and rear together. A number of times on RT 81 in Southern NY State I had to do this just to make it through. You could sure tell when you had in 4WD High, it just seemed to lock itself down and track so well in the icy conditions.

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[jeepoch]

All,

Also as a follow up to Chis' comment above, many people try to force their way between 4Hi and 4Lo thinking that over time it should get better. He does give sound advice to exercise both differentials under power occasionally, if nothing else to practice and ensure everything is in good working order when needed but it should never be difficult. If you ever need to force something that's when things break.

The primary reason it's sometimes so hard to get it into 4Lo has little to do with 'breaking' anything in but rather more of needing to mesh the gearing properly.

From 2wd to 4Hi, you're only applying power to the front differential (pumpkin). In fact there are no changes to any gearing whatsoever. So dropping into 4Hi you can typically accomplish this rather easily up to 45mph or even higher. Just shifting into transmission neutral before making the change to either 4Hi or 2wd (just to reduce output torque) should be all that's required before shifting the transfer case lever.

However, dropping into 4Lo is a different animal. This requires the change into the much lower gear ratios, 2.72:1 on the Sports and Saharas and 4.00:1 on the Rubicon's. This gear change requires the meshing of this new gear set. It's easy if the teeth and the cogs are all in alignment. Difficult to impossible if not. Recall, there is no clutching action involved with helping this alignment, so it's either going to be easy (when in natural alignment) or hard (when not). When stopped, it's binary, one or the other. Either easy or difficult to impossible.

The trick is to use just a very low speed (2 to 3 mph) to provide just enough movement of these gears to 'mesh' cleanly. It doesn't matter whether going either forward or reverse, just slightly moving is the key. Then as above shift the transmission into neutral, then make the shift from 4Hi through transfer case neutral and then into 4Lo. With some practice you'll get the feel of the best speed where the transfer case meshes with the lower gears with absolutely no trouble.

Remember, if you struggle or hear grinding, the teeth are not meshing. This means you are not at a good meshing condition (very slow) or you are applying way to much force to the transfer case shifting lever. One of the most typical of indications when the gearing hasn't meshed properly or the teeth have ground (shaved) down to the point of rounding, it becomes very easy to fall out of low gear.

The exact same process is also needed when shifting back to 4Hi. With a little practice, you will soon find that every change into, or out of, 4Lo should be both easy and smooth.

Full time 4WD has it's nuances, just like a manual transmission changing into or out of low gear isn't 'automatic'. That is exactly why Part Time 4WD and All Wheel Drive systems were invented.

Jay

 

[txj2go]

@Sigil,
Simon, you'll continue to likely receive the input of something like "just don't do it". Unfortunately without much reasoning as to why.

Nobody has really explained "why" yet. When the transfer case is engaging both differentials, the transfer case is essentially locking front and back differentials together meaning it only allows the driveshafts to turn at the same speed. Now when you are turning and the wheels are traveling different distances and they want to turn the driveshafts at different speeds, the transfer case won't allow it. The transfer case will force one driveshaft to turn faster than it wants to, or slower than it wants to and somewhere some tires will have to slip. Whichever transfer case version is in the Sahara and has alltime 4WD probably has some spider gears or something similar to handle this in normal driving. Similarly if you have a Rubicon you don't want to use the lockers in the axles unless you are on conditions with traction problems.
Many years ago one of my hobby cars had a spool in the rear differential. It was fine when driving straight but when turning you could hear one tire slipping. This wasn't an every day driver but we did drive it quite a bit on weekends and it never caused any problems. It's the same concept as the locked part of the transfer case, two of the spider gears in the differential were removed and the other two were welded to the carrier so the 2 axles had to always turn at the same speed.

 

[GATORB8]

Whichever transfer case version is in the Sahara and has alltime 4WD probably has some spider gears or something similar to handle this in normal driving.

MP3022, clutches.

Standard on 4xes and the 392, optional on several other trims, including the Rubi. The 4:1 Rubi case is designated as MP3022OR.

In 4 Auto the clutches can disengage and vary the connection. In 4Hi/Lo it operates (at least in my observation) as fully engaged and just like the 241.

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