Trouble engaging into 4H

[Elsinore73]

Had something odd happen this morning and wondering if anyone can shed some light on it.

Have a 2021 JLUR 6cyl 6spd. We got about 6” of snow last night, went to pull out of the driveway this morning, popped it into 4H at a slow roll, dash indicated 4H, but when I went to accelerate the rear tires were spinning, front tires did nothing. Tried backing up, rolling forward, nothing. I stopped and went into 4L, that engaged. Got up the hill I live on and went into 4H and it held the for rest of my drive.

I have had this jeep over a year and 13k miles, used 4H many times but never experienced this. Any thoughts?

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[Pinky Tuscadero]

It simply didn't engage...yet, but would have as sometimes they just need to mesh and its not always instant
Might want to keep an eye on the weather and just engage it when you get home the day before so your sure you don't get stuck as it can be rather embarrassing to have your new 4x4 stuck in the driveway while the man next door who wears a dress comes out to warm up his Prius and see's you struggle and offers to help push you.....
Just sayin.....
But yeah, they don't always engage or disengage instantly so probably not an issue but keep testing it and obviously take it in if it keeps happening

 

[DavidArmen]

I am still unsure why mechanically, but I can tell you that four wheel drive on the JL doesn’t engage right away. Even though we have a mechanically linked transfer case lever, engagement has a lag and requires acceleration. You need to let go of the brake pedal and accelerate for at least a 1-3 seconds after shifting into 4H, in order to make the jeep actually go into 4H, but that doesn’t always work either. I believe it has something to do with the FAD, but I am as of yet unsure.

Same thing applies when shifting from 4H to 2H. You need to accelerate after shifting into 2H to make the jeep actually physically go into 2H. Sometimes even acceleration doesn’t do it.

Your scenario is a great example of this. Your jeep was simply not yet physically in 4H, even though the tcase lever and the dash light indicated that it was.
On the other hand, if you are in 4H and you come to a stop and then you shift to 2H and then immediately make a hard left/right turn, your front tires will hop because your jeep will still be in 4H even though you shifted the mechanical lever to 2H before letting go of the brake to make the turn.
It’s very bizarre and unexpected especially when our transfer case shifter is not electronic.

 

[Elsinore73]

I am still unsure why mechanically, but I can tell you that four wheel drive on the JL doesn’t engage right away. Even though we have a mechanically linked transfer case lever, engagement has a lag and requires acceleration. You need to let go of the brake pedal and accelerate for at least a 1-3 seconds after shifting into 4H, in order to make the jeep actually go into 4H, but that doesn’t always work either. I believe it has something to do with the FAD, but I am as of yet unsure.

Same thing applies when shifting from 4H to 2H. You need to accelerate after shifting into 2H to make the jeep actually physically go into 2H. Sometimes even acceleration doesn’t do it.

Your scenario is a great example of this. Your jeep was simply not yet physically in 4H, even though the tcase lever and the dash light indicated that it was.
On the other hand, if you are in 4H and you come to a stop and then you shift to 2H and then immediately make a hard left/right turn, your front tires will hop because your jeep will still be in 4H even though you shifted the mechanical lever to 2H before letting go of the brake to make the turn.
It’s very bizarre and unexpected especially when our transfer case shifter is not electronic.

Thanks and I agree it’s often not instant but I went forward 20-30’ after engaging, then rear tires started to spin. I backed up 20, then forward again with only rears spinning. Certainly should have engaged by then I would think. It Went into 4L instantly at a full stop, then no issue going into 4Hi once I drove up my block. Have had many 4wd vehicles over the years and this one is new to me, weird

 

[word302]

Thanks and I agree it’s often not instant but I went forward 20-30’ after engaging, then rear tires started to spin. I backed up 20, then forward again with only rears spinning. Certainly should have engaged by then I would think. It Went into 4L instantly at a full stop, then no issue going into 4Hi once I drove up my block. Have had many 4wd vehicles over the years and this one is new to me, weird

Sounds like you just didn't quite have it engaged properly. Could be an adjustment issue but it's pretty easy, especially when new, to pull the shifter back butt not get it fully engaged. The light will say 4 hi but you're still in 2 hi.

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