To 4x4 or Not?

[jeep229]

We finally got a little snow around here last night. The roads were covered and slick this morning. Since hanging around this board, I have become more aware of how vulnerable my D35 with Trutrac LSD really is. So, when driving on a slick surface with some bare spots, am I better of leaving the jeep in 4WD drive even though I don't really need it? Or, do I just run 2WD? Keep in mind that I am taking it easy on the skinny pedal. TIA

[OhioYJ]

If I'm having trouble getting going, like the Jeep wants to just spin tires, I use 4x4. If not I just use 2WD.

[Dk]

I dont see a problem using 4x4 if you are goign slow and the roads are slick. I have used mine alot this winter without any problems. i ussually just use mine on takeoff if its really slippery then when i get going go back into 2. but if the roads are liek 90 percent snow with the occassional dry spot and you keep her under 40 i dont think you will do much damage. But dont quote me on that. i once drove a s10 in 4x4 for liek 3 hours at 60 mph before i noticed it was in 4x4. And that was one of the older ones that didnt have that push button all the time crap.

[kwrangln]

Knowing when to use 4WD off road is easy, when you hit the dirt or gravel, grab the lever and go. When on pavement its a bit trickier. Blindly using 4hi anytime a flake falls from the sky or the temp drops below 32 isn't such a good idea. When in 4wd, there needs to be some slip to aleviate drivetrain bind. What the heck is drivetrain bind? Next time your in the dirt, drive in a half circle, stop, get out, and look at the tire tracks. The front takes a wider circle than the rear, it covers more distance. When in 4wd, the front and rear ends are locked together, so this difference in distance traveled has no way to excape, in dirt, the tires slip, on pavement, it binds the drivetrain. There have been cases where this has led to catistrophic failure, transfer case goes bang, but most of the time it wont blow up. What does happen, is stress placed on the transfer case will over time stretch the chain leading to replacement.

So, how do you know when there is enough slip to use 4wd without stressing the drivetrain? Easy. While in 2wd, if you think road conditions warrant the use of 4wd, gently blip the throttle. Dont floor it and hold it, or you'll be doing unplanned doughnuts before you can say "help!". Just quickly hit the gas and release back to where it was. If you feel slip, engine rpm's pick up without feeling acceleration, then there is enough slip to use 4wd. If you feel acceleration, its too dry, stay in 2wd.

Once in 4wd, you can perform the same test, quick blip of the throttle, if you dont feel acceleration, stay in 4wd. If you dont feel any slip, back to 2wd ya go. When traveling on snowy roads, its not uncommon for me to shift into and out of 4wd a dozen or so times depending on how far I'm going. The modern jeep transfer cases have no problem shifting on the fly and do just fine up to 55, if you're going faster than that while still passing the 4wd test, then you need to just go home, you're too dumb to be on the road.

Hope this helps a bit, its been working for me for about 15 years or so now.

[DeadHopeless]

Originally posted by kwrangln:
What the heck is drivetrain bind? Next time your in the dirt, drive in a half circle, stop, get out, and look at the tire tracks. The front takes a wider circle than the rear, it covers more distance. When in 4wd, the front and rear ends are locked together, so this difference in distance traveled has no way to excape, in dirt, the tires slip, on pavement, it binds the drivetrain. There have been cases where this has led to catistrophic failure, transfer case goes bang, but most of the time it wont blow up. What does happen, is stress placed on the transfer case will over time stretch the chain leading to replacement.
Informative- as always. Never really thought much about this...

[jeep229]

Originally posted by jeep229:
We finally got a little snow around here last night. The roads were covered and slick this morning. Since hanging around this board, I have become more aware of how vulnerable my D35 with Trutrac LSD really is. So, when driving on a slick surface with some bare spots, am I better of leaving the jeep in 4WD drive even though I don't really need it? Or, do I just run 2WD? Keep in mind that I am taking it easy on the skinny pedal. TIA I wrote this in a hurry earlier and while there is a lot of great information that I hadn't considered, I think I need to reword my question. My concern is more with accelerating and one rear tire catching a patch of dry pavement. Would being in 4WD take some stress off of the rear axle?

[kwrangln]

Dont worry about it. The trutrac takes a revolution or two in order to bind the worm gears and transfer torque to the other side. Unless you're doing high rpm power slides, it wont hurt a thing.

Look at it like this, ya take off on ice, both tires turning the same speed slipping. Hit a dry spot with one wheel, it stops spinning but the other side still is, taking up the shock load. Once power transfer takes place in the truetrac it is not a light switch, it has a bit of cushion there.

Like I said, dont worry about it, keep the 5K rpm clutch drops to a minimum, try not doing donuts, and you'll be fine.