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Discussion Starter · #1 ·
I'm sure this has been answered somewhere before, but I'm not sure what to search for.

My question is this. I've heard tons of conflicting opinions on this issue, and I'd like it clarified if possible.

I was always under the impression that 4 low is the only thing your not supposed to use on road, as the gears aren't meshed properly and the front tires need to be able to slip a bit.

I was also under the impression that 4 high is perfectly fine to drive on road, as long as you switch into 4 high at 55mph or under.

Now, I've heard it both ways. I've heard people say you can't use 4wd high or low on the road at all or you'll blow your transfer case.

I use 4 high when its raining bad, or in hazardous conditions on the road so I have a better chance of being able to correct something if my backend slides out. Is this bad to do? Am I hurting anything?




-Brandon
 

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As long as you can ensure slip then ya you can do it makes no difference between 4lo or 4hi but with 4lo you don't really want to do more than 25 anyway.

If you have lockers and don't get road slip then going around corners can bind and load up the rotating components. It's only the t-case that you are binding if you have open diffs front in rear.

If you have a lever you can wrench it back out of 4lo but once your shit gets mileage on it I have had a hard time getting it to back out. Now with the damn knob on my Excursion sans the lever I've had it not want to leave 4hi when it was cold twice.

Look at a worn out front axle in full time 4wd vehicle like a ZJ and you will see why you should still try to spend as much time in 2wd on pavement in most MI weather. Just useless wear and tear and - gas mileage.
 

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You can use four wheel drive (high or low) on the road if you want to. On dry pavement, it will handle differently, as you probably know. There is no difference mechanically between 4lo and 4hi. The only difference is the gear reduction in the t case. Jeeps have a locked center diff (t case), so the front and rear axles get equal power all the time, which causes binding, pulling, etc. when it is on dry pavement where the tires have good traction. You can shift on the fly into 4hi, as long as both axles are spinning at the same speed. If you are spinning your rear tires when you try to shift into 4wd, you will get a grinding sound.
 

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there are 2 types of transfercases. full-time and part-time. a full-time transfercase has a differential in the transfercase. with those t-cases, you can leave it in 4wd full-time all year round regardless of condition.

with a part-time t-case, you can use 4hi on the road when it's raining or snowing. but when it's dry you should leave it in 2wd. those t-cases weren't really meant for continuous dry 4wd.

if you are talking about an xj, the 2 t-cases would be the NP231(part-time) and NP242(full-time).

shift patterns

NP231 part-time 2wd-4hi-N-4lo

NP242 full-time 2wd-fulltime 4wd-parttime 4wd-N-4lo (i might have the order on this one mixed up, but those are the options on that t-case)
 

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well then on the TJ it would be the NP231.

but the same idea still goes for your dodge. and if you absolutely want to be sure what your t-case is supposed to do, then check out your owners manual.
 

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hey i was just giving examples of when it would be ok to use it. not that rain requires 4wd. then again, there are 2 turns in my general area that can get a little ugly when it's raining hard enough. specially since my rear axle is welded and the tires suck in the rain. so between all of those things, yeah....sometimes i actually have to use 4wd otherwise i have to crawl through that turn.
 

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Bascially, it boils down to this:

If you are driving 4wd, hi or low (unless you have a full-time case, which TJs and most Rams don't), then your front and rear axles are turning at the same speed.

When you go around turns, your front needs to turn faster than the rear. You are binding your drivetrain. If there's snow (or rain for sissys), your wheels can slip enough to release the binding. Otherwise a tire has to slip on dry pavement. The amount of force it takes to do that is obviously quite a bit, and strains your drivetrain, eventually you would break something if you did it all day long.

The effect will be much worse in the heavier longer wheelbase ram.
 

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Discussion Starter · #17 ·
4wd in the rain? for real?

Yea. The Ram I'm talking about has like 350 horse, 700 foot pounds of torque. And absolutely no weight on the rear end. It'll slide out on you easily.

My Jeep I only use 4wd in the rain when the roads flood, so I don't loose control when I'm going through puddles.

I deliver pizza's, so you must understand that the likeliness of me getting into a shitty situation during rain, snow, etc is much more than the average driver.



-Brandon
 

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4wd in the rain? for real?
Yea. The Ram I'm talking about has like 350 horse, 700 foot pounds of torque. And absolutely no weight on the rear end. It'll slide out on you easily.
You don't even need to have a lot of power in a long wheelbase vehicle - like a pickup that's unloaded. It'll spin tires and kick out very easily. I would use 4wd in the rain frequently when my Ram was my DD.
 

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My Jeep I only use 4wd in the rain when the roads flood, so I don't loose control when I'm going through puddles.



-Brandon
the reason you lose control in the puddles is because your going to fast through them and begin to hydroplane, 2wd or 4wd has nothing to do with it.
 
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