When to use/not use 4x4? Overheating diffs, transfer cases etc.

[JTdiRtyD]

Lately I've been hearing more and more about overheating transfer cases, diffs, and transmissions while off-road. I recently listened to a podcast where the host was saying to stay in 2H until you need it, and if you do need 4x4 to use 4L and in leave your trans in 1st or 2nd. They stated 4H is for inclement weather at 30-50mph, not for slower speed off-roading, you'll over heat your transfer case or front diff running in 4H on the trails.

On that same token I've also heard to stay in 4H on trails because you don't want to find yourself in a situation where you need it but it's too late to engage it, and always engage 4L before entering anything that might warrant the need.

What say you?

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[Thunderspud]

Everyone will have different opinions based on their specific use case and experience. That said, seems like the only objective answer to this would be to trust the section called "FOUR-WHEEL DRIVE OPERATION" in the Owners Manual. Begins on page 164 in mine.

 

[JTdiRtyD]

Everyone will have different opinions based on their specific use case and experience. That said, seems like the only objective answer to this would be to trust the section called "FOUR-WHEEL DRIVE OPERATION" in the Owners Manual. Begins on page 164 in mine.

TBH the manual doesn't give a lot and is very vague/generalized. Per the manual;

"d. The 4H
and 4L positions are intended for loose, slippery road
surfaces only and not intended for normal driving. Driv-
ing in the 4H and 4L positions on hard-surfaced roads
will cause increased tire wear and damage to the drive-
line components."



I guess I just don't understand this whole overheating argument lately and curious what folks say. Sure, t-cases will get warm but do does your rear diff. They're designed for it. Hearing to not use 4H on trails just blew my mind. I've always been, and will continue to be an advocate for using 4H. If you're off the asphalt and on dirt, use 4H even if the trail doesn't necessary warrant it. 4H can save your drivetrain from added stress, it saves the trail from ruts and throwing rocks if your rear tires slip, and it's peace of mind that you have the traction when you need it.

 

[MikeNH]

You’re not going to overheat a diff on anything short of full trophy truck stuff and the t-case has power going through it any time you are in motion so you aren’t saving anything by running it in 2wd. The 4H/4L debate can be a bit two sided-

Mechanically I’d say 4L for anything beyond the most mild trail work. You’ll have better throttle control for technical stuff and it is less strain on the engine (think pedaling up a steep hill on a bicycle in high gear vs low) but the sustained higher RPMs may elevate engine temps. Gotta use judgement. When I had my JK, it was a two door with 4.10s and the automatic so it was really short geared even in 4H and being a Rubicon, the 4:1 low range was way overkill for the trails I was on at the time so despite the “always 4L” crowd, I didn’t. I kept an eye on temps and used it as needed. That said, at least on JKs, that 4:1 low range was a pain to shift into some times so you could bone yourself by waiting till it gets bad on the trail.

 

[fourfa]

...you'll over heat your transfer case or front diff running in 4H on the trails.

Interesting that the rear diff doesn't overheat in 2H, but they think if you divide the engine power in two, sending half to the rear and half to the front, now all of a sudden the front diff will overheat with half the power input? Similar differential size, same fluid capacity, very similar axle housing...

Does not sound like this podcast host knows much about Jeeps. Perhaps there are some ass-spec vehicles out there not really equipped for running 4WD for long periods, IDK, who cares. Gladiator/Wrangler is not one of those

 

[Zachanadandy]

The overheating argument is just dumb. The JLs don't even come with a fad anymore, which means the ring and pinion and front drive shaft are spinning in 2wd. Guess what, no overheating. If using them caused overheating how could you drive down the road? Wouldn't the rear diff overheat? Now 4A off road can cause overheating of the clutches in the transfer case caused by too much slip but that's a different scenario. I'll use 2wd on easy trails and dirt roads simply because it steers better. 4HI can be run at freeway speeds, which is common in inclement weather and in the desert/sand. 4LO, especially in a Rubicon is too slow for all but the most technical trails.

 

[Hootbro]

The JLs don't even come with a fad anymore,................

Is that across all models? I knew the 392 does not have it, but the other models I am unaware of that being a change.

 

[Zachanadandy]

Is that across all models? I knew the 392 does not have it, but the other models I am unaware of that being a change.

That's what I read recently over there. The 2025s even without 4A don't have a fad.

 

[TheSolarWizard]

I dont understand how using 4 hi will overheat the transfer case when it moves at the same speed as 2wd.

 

[Hootbro]

That's what I read recently over there. The 2025s even without 4A don't have a fad.

Thanks. Poked around over there and it seems to have started to be phased in with the FAD delete in 2024.

Makes me wonder why they have chosen to keep it on the JT?

 

[MikeNH]

Thanks. Poked around over there and it seems to have started to be phased in with the FAD delete in 2024.

Makes me wonder why they have chosen to keep it on the JT?

They haven’t. My 2024 Mojave does not have it either and it does not have the 4 auto t case.

 

[ShadowsPapa]

I recently listened to a podcast where the host was saying to stay in 2H until you need it, and if you do need 4x4 to use 4L and in leave your trans in 1st or 2nd. They stated 4H is for inclement weather at 30-50mph, not for slower speed off-roading, you'll over heat your transfer case or front diff running in 4H on the trails.

The only difference is that in 4L the engine RPM is up, and t-case RPM is up. The axles aren't doing anything different between 4L and 4H.

I've dealt with a certain car make and model that flipped back and forth between FAD, no FAD, and various combinations of transfer cases and just can't see any logic in that podcast - but these days, anyone with a microphone and internet can be an expert.

 

[ShadowsPapa]

I dont understand how using 4 hi will overheat the transfer case when it moves at the same speed as 2wd.

Should be the opposite as you have a lower input shaft speed in 4H. Makes zero sense.

 

[Figmo]

Ignore your 1st paragraph about all that overheating nonsense. Your 2nd paragraph is the answer to your question.

 

[Zachanadandy]

Ignore your 1st paragraph about all that overheating nonsense. Your 2nd paragraph is the answer to your question.

I'm not a fan of the tfl way of wheeling either. No I don't need 4HI to drive down a dirt road or 4LO and lockers because I have to drive over a decent sized rock. You can shift into 4HI at freeway speed, just how slow are your hands and how nearsighted are you that you'll be cruising down a forest road and suddenly it's too late to put it in 4wd? I've also found in decades of experience that the guy over using every tool in the tool box is the one who gets stuck the worst. Most times if you drove into a situation in 2wd you can back out in 4HI. Got yourself hung up in 4HI, 4LO and lockers and you drive right out. If you started off in 4LO with the lockers on now you're REALLY stuck or you've broken parts from the added stress of much more torque and locked diffs. I prefer the minimal tool for the job until the job warrants bigger tools.

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