4WD Auto questions

[TheRaven]

Can you provide a source for this claim?

I already did...

https://www.jlwranglerforums.com/forum/threads/4wd-auto-questions.123903/post-2586068

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[bugnuker]

I have the 2024 with the same transfer case you have.

I have had extensive snow driving already this year and I can tell you a few things.

In 4H FULL TIME (AWD) - the Jeep is putting all the power to the rear wheels, UNTIL they slip. Once they slip, this activates the front. It is pretty quick to activate. This is using a clutch system, and there is wear involved on these parts, albeit low. For example, 392 Jeeps have this mode on all the time - there is no 2WD mode for a 392. (unless you hack things)

In 4H PART TIME - The jeep is always putting some power to the front and the rear.

When I am out on some snowy back roads or parking lots, and I'm having a little fun with the snow, you can feel the 4H FULL TIME kicking in. When I am in 4H PART TIME, it's a different feel. It feels better and stronger than 4H FULL TIME. With that said, I only use 4H PART TIME when I am on roads that are snowy or slippery or off-road. If the conditions are moving from some traction to slippery roads (for example, a paved road that has some snow and ice, but also has spots that are clear) - then I use 4H FULL TIME.

You can move from 2WD to 4H PART TIME and 4H FULL TIME easily. From things I've read, you can switch between these modes at any speed under 50MPH. That is NOT the case for 4L. 4L needs very low speeds or no speed.

 

[JLfromCA]

Full-time four-wheel-drive (4wd auto) Jeeps have no FAD. Or front axle disconnect and CV front axles. The front driveshaft is spinning 100% of the time. The part-time transfer case the driveshaft only spins when you have it engaged. You can test this theory yourself go underneath your jeep and try to turn the front driveshaft. It will not turn if you have full-time four-wheel-drive. Or Auto setting. If you have the part-time transfer case the front drive shaft will spin by hand.

 

[Mr.Smith]

Thanks for all the info guys I appreciate it.

 

[Yawnie'sPapa]

Does it do any damage to leave in 4 auto all the time. I ask because wife drives and I doubt she will remember to go back and forth

No damage, and really no added wear. Once you get up to about 18 mph or so, the clutches release and would only apply again under very heavy throttle and so on.
Because of how the clutch packs apply and release, it seems impossible to constantly be connecting the fad, disconnect, reconnect, disconnect, at every stop light, every time you punch the throttle. So........ they don't use it.

The 4xe only comes with the SelecTrac - because of the torque.
A fellow has used JSCAN to monitor the application of the clutches in the transfer case and it's NOT only on loss of traction that they are engaged.
I run in 4HA when plowing snow. It's totally amazing.
A couple of 4xe owners who have done some testing on how it works say "just leave it engaged"

 

[Mr.Smith]

No damage, and really no added wear. Once you get up to about 18 mph or so, the clutches release and would only apply again under very heavy throttle and so on.
Because of how the clutch packs apply and release, it seems impossible to constantly be connecting the fad, disconnect, reconnect, disconnect, at every stop light, every time you punch the throttle. So........ they don't use it.

The 4xe only comes with the SelecTrac - because of the torque.
A fellow has used JSCAN to monitor the application of the clutches in the transfer case and it's NOT only on loss of traction that they are engaged.
I run in 4HA when plowing snow. It's totally amazing.
A couple of 4xe owners who have done some testing on how it works say "just leave it engaged"

Very good information. Thank you

 

[jac04]

Full-time four-wheel-drive (4wd auto) Jeeps have no FAD. Or front axle disconnect and CV front axles. The front driveshaft is spinning 100% of the time. The part-time transfer case the driveshaft only spins when you have it engaged. You can test this theory yourself go underneath your jeep and try to turn the front driveshaft. It will not turn if you have full-time four-wheel-drive. Or Auto setting. If you have the part-time transfer case the front drive shaft will spin by hand.

I have a 2021 JT with Selec-Trac (4wd auto as you call it), and it has FAD and the front driveshaft does not spin 100% of the time. Has something changed?

 

[JLfromCA]

I have a 2021 JT with Selec-Trac (4wd auto as you call it), and it has FAD and the front driveshaft does not spin 100% of the time. Has something changed?

This is a JL forum. I’m speaking strictly about the JL. Also, the title of the thread is 4WD Auto. It’s not just me calling it, that that’s what it is. I didn’t mention selec trac.

 

[GATORB8]

This is a JL forum. I’m speaking strictly about the JL. Also, the title of the thread is 4WD Auto. It’s not just me calling it, that that’s what it is. I didn’t mention selec trac.

Selec Trac is the name for the 2.7:1 full time system. They use Rock Trac for both 4:1 cases.

We also have a FAD.

 

[AFD]

Can you provide a source for this claim? The only source I have seen so far seems to say it is in fact disengaged, just like every other Auto 4WD system ever.

The really confounding part about this is - if it is true that the front axle is always engaged in Auto 4WD, then it's actually AWD...so why would FCA not just call it that?

"For variable driving conditions use 4H AUTO which engages the front axle but sends the vehicle's power to the rear wheels. If the vehicle senses a loss of traction, it automatically engages 4WD. Because the front axle is engaged, this mode gets lower fuel economy than 2H position."

 

[Boatbuilder88]

Does it do any damage to leave in 4 auto all the time. I ask because wife drives and I doubt she will remember to go back and forth

No damage but likely a decrease in MPG.

 

[RecessRampage]

Should you change modes while moving or when stopped? Does it matter (as long as it's relatively lower speed like below 50mph)?

 

[JLfromCA]

there is no 2H high setting on the 4WD auto transfer case. Example the 392 has no fad, CV axles auto setting full-time four-wheel-drive.

 

[AFD]

there is no 2H high setting on the 4WD auto transfer case. Example the 392 has no fad, CV axles auto setting full-time four-wheel-drive.

The 4xe and 392 have full-time 4WD, but not a selectable 2WD. The Selec-Trac and Rock-Trac full-time 4WD option (now discontinued, iirc) has 2HI, 4HI-AUTO, 4HI and 4LO.

Watch the video I posted above. They're very similar, but different.

 

[jac04]

there is no 2H high setting on the 4WD auto transfer case. Example the 392 has no fad, CV axles auto setting full-time four-wheel-drive.

The 392 is different. The 392 comes standard with Selec-Trac, but it does not have a 2H setting. Non-392 JLs with Selec-Trac have the '4WD auto transfer case', and they also have FAD and a 2H setting.

Selec-Trac is Jeep's name for what you and others are calling "4WD auto transfer case".

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