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SKOOL ME? 242 shifter positions.

Hypoid

NAXJA Member
NAXJA Member
Location
Golden, CO
OK, so I'm a newb to the XJ, and it's with some embarrasment that I have to bend my stiff neck and ask a simple question. BUT, I have been under this shady tree long enough to know that auto makers invent different names for simular equipment, and like names for different equipment. Specifically referring to a '90 Limited, 4.0, auto overdrive, NP 242 TC.

So the question is: when I have the transfer case shifted into the "4-part time", "4-full time" positions, what is going on with the driveline? What conditions warrant using one over another?

2-wheel drive, Neutral, and 4-Low i think I have figured out...:confused1

TIA, Mike
 
Full time is for use, well, full time, if you wish, on any surface. Part time is only for use on slick or loose surfaces. In full time, the planetary gears in the 242 allow the front and back wheels to turn at different speeds, thus eliminating the tendancy for the TC to bind up as it would in part time if run on dry surfaces (part time locks front and rear together for maximum traction).
 
4 HI Full Time - may be used at pretty much any time. It's one step down from All-Wheel Drive, you can use it if you're anticipating weather, but it hasn't hit yet. There is a differential in play that will allow the front and rear driveshafts to turn at different rates.

4 HI Part Time - typical four-wheel drive setting, you should not use then when you would normally have traction (like on dry pavement.) This setting effectively locks the front and rear driveshafts together with no gear reduction after the transmission. Extended use on drive pavement will eventually result in transfer case damage - if you're lucky, you'll just stretch the drive chain.

Neutral - uncouples all output shafts from the input and each other. Use for flat towing.

4 LO Part Time. Similar to 4 HI PT, but also includes gear reduction (should be 2.72:1 for the NP242) and can be used when extra torque or extra "grip" is needed to clear an obstacle of some sort.

Speed Limits -
4HI FT - typically 65mph or lower. Can be run up to 75mph, based upon experience - but not recommended.

4 HI PT - typically, 55mph. You should probably not be driving that fast anyhow, since you're likely in snow or mud.

4 LO PT - 25mph or less. With the additional gear reduction, you'll need to keep low speeds so you don't over-rev the engine anyhow...

"There are no stupid questions, only questions unasked." While not always strictly true, if you ask the question and learn something from the answer, it wasn't stupid to ask!

5-90
 
LMAO guys, I knew there was a trick involved! My old '74 has a Dana 21, I bought a NP 235 to upgrade; yep, all gears inside, no differential. My butt-o-meter has served me well in the truck, I don't outdrive the tires (often) and I understand the phrase: "stupidity to the fourth power". So even if you are in the "full time" position it is still possible to break traction at all 4 corners and lose any benefit of the directional tread? (aka: out-drive the tires) Hmm, there's no clutch to push in; how quickly does the tranny respond when you take your foot off the throttle?

Now I have an idea what to tell the Mrs. Thanks for the quick response.
 
The AW4 is simple, solid, and fairly quick - I've got three rigs with AW4s in them.

It is always possible to break traction at all four corners - some things just make in incrementally more difficult. "Never underestimate the power of pure stupidity - ignorance runs a close second." Therefore, it's a very good thing you've asked this question - it shows you're not stupid, and you're not ignorant anymore!

If you want compression braking in the AW4, it's fairly decent about being "pulled down" via the shifter - if you want full manual control, contact BrettM (www.awshifting.com is his site, I think.) I'd like to get a kit like that myself, if I didn't already have a DD with a stir-yer-own gearbox.

If it's her DD, and you want to improve things slightly, I have found that the BFG AT/KO in stock size (or 30's) serves very well, has good road manners, and wears well. You should be able to fit 30's without a lift, if you're dealing with a road/street rig (I've got 30's on a couple of stockers, and they handle streets, gravel roads, and fire roads rather well. Don't have lifts, so don't spend a lot of time off-road. Yet.)

Bear in mind a couple of things:

4HIFT is not AWD - don't treat it like it is. I don't recall the differences, but there are differences. Just because it sez "full time" doesn't mean you can run it all the damn time!

Just because you have more "go control" doesn't mean you have more "whoa control" - you probably know this, but I did have a learning curve issue with my wife (who is actually a very good driver - just didn't have any 4WD experience) and it bears mentioning. You do have some more control in the snow and wet as well, because you're driving and steering with the same wheels up front - but that don't make you stop faster. You still need to think ahead in the white stuff - but you do have more options.

5-90
 
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