Should I be able to change into 4WD on the fly?

[Jerry]

Just wondering guys. My truck doesn't like it! Changing on the fly that is. I thought you were supposed to be able to change at up to 70mph in these trucks? It's been snowing alot round here and some roads are clear in places and covered in others so I've been trying to change in and out of 4WD at about 15mph. Some times it goes in with a bit of a "crunch" sound and other times it just won't budge unless I stop. Comes out fine though. Last night I tried again at low speed and it made a real worrying "bang!!" noise :eek:

Please can someone explain what the correct method for changing is, if there is one?!

Thanks loads

 

Disclaimer: It's my first ever jeep of any kind so that's why I'm a technical :dunce: And, it's my only car so throwing it in the garage to install a 4.0L with a better gearbox is not an option, I need it on the road :thumbsup:

[Geonovast]

Check your fluid level. Mine was getting low on fluid and was having trouble getting out of 4wd.

 

Generally its not a good idea to run at 70 in 4wd unless you have a Full Time case. At those speeds, the minute difference in ratio and tire size would be enough to grenade something if all 4 tires hit dry pavement at the same time.

 

Oh, I would also check the vac lines to the CAD. Or just lock it over so its always engaged, at least for diagnostic purposes.

[Jerry]

OK, thanks Geonovast. Although that doesn't quite answer my question ;)

I have had the transfer case oil changed recently and it doesn't leak so the fluid should be good.

My real Q is: should I stop completely to change the lever into 4WD or am I supposed to be able to change into 4WD while the vehicle is moving?

Thanks :cheers:

 

edit: the 4WD all works fine once engaged so all the mechanisms (CAD etc) are doing what they are meant to :thumbsup:

[CWLONGSHOT]

Like I tell my wife. (She is a lead foot) If you can go 60+ you DO NOT NEED 4WD!!! I do not allow driving above 45 in 4WD in my vehicles. YES, you can ahift on the fly. But only into 4HI. I like to only do so at lo speeds and even then I let off the throttle. Disengageing is exactly the same, let off the throttle, sharply push it out and into 2WD.

 

As usual, Geonovast has given good advice. Check all those fluids and the front CAD too!!

 

CW

[Jerry]

Awsome! Really appreciate the advice guys! :thumbsup:

This is such a good place to be a newby :bowdown:

So then, my nasty noises when attempting to change (at low speeds) on the fly suggest either I have a bad transfer case or it's low on fluids. I'll check out the levels asap........

[BLHTAZ]

Yes...you should be able to shift on the fly, but I thought it was only up to 50 MPH.

 

Personally, I am like CW and slow down or stop to do it.

[DirtyComanche]

You can shift-on-the-fly at almost any speed... Or you should be able to. The trick is having the wheel speeds all relatively equal, so going straight without having the rear tires spinning is best. The case might be a little worn, and thus not so happy about synchronizing. Short of a rebuild, too bad.

 

I'd probably drive around town with it in 4wd all the time. That's what I did before I got my dodge... With it I shifted in and out, and what do you know? I broke the freaking tcase.

[Eagle]

Awsome! Really appreciate the advice guys! :thumbsup:

This is such a good place to be a newby :bowdown:

So then, my nasty noises when attempting to change (at low speeds) on the fly suggest either I have a bad transfer case or it's low on fluids. I'll check out the levels asap........

Or that you have your foot on or off the throttle.

 

Shift on the fly going INTO 4WD only works if the front and rear wheels are turning at the same speed. If the front wheels are rolling along at 30 MPH but the rear wheels are on slippery stuff and spinning at 45 MPH ... what do you THINK is likely to happen if all of a sudden the transfer case tries to lock both drive shafts together?

 

The name of the game is "neutral throttle" -- ideally you should be on fairly level ground so you can "feather" the throttle so you are neither accelerating nor compression braking. That ensures that the rear wheels won't be spinning faster or slower than the front, allowing for a smooth shift into 4WD.

 

And I agree -- if the conditions call for 4WD, one definitely should not be going 70 MPH, or anywhere near 70 MPH.