Chazzard
Well-known member
Wondering how the 392 with the full time 4wd handles on dry pavement while in tight maneuvers. Do you get the typical Binding/fighting that you would get in a typical 4WD truck on dry pavement.
Question about the full time 4WD
- Thread starter Chazzard
- Start date
Not at all, power isn’t going to front all the time, just when it needs it.
Fast-n-Furious
Well-known member
Read this and you’ll have a better understanding: https://www.hagerty.com/media/maint...details-that-make-jeeps-wrangler-rubicon-392/
392’s 4H auto is designed for dry pavement.
- Sep 14, 2021
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Thank you. This was the article I recently came across and couldn’t locate again.
Power is sent to the front axle when in 4H Auto, and the rear is activated when the computer calls for it. 4H Part locks the transfer case. You can see this when you are view the Offroad screen in the vehicle screen option.
I have not experienced any binding while turning.
hardhat
Well-known member
From wikipedia:
The MP3022 transfer case uses an electronically controlled clutch pack to bias torque from 100% rear to 50/50% front/rear. The transfer case has no center differential, so power can only be supplied to the front axle when the rear wheels begin to slip.
What follows is just my current beliefs. Not gospel truth. I could be wrong, but the only time I've been wrong, was one time when I thought I had made a mistake
. Maybe can start a discussion that will improve all of our understanding..My understanding at this point is that rear wheels are engaged all the time and that the clutch is electronically controlled and can go from 0-100% engagement. As it engages it starts transferring power to front shaft, but can still allow slip between front and rear to account for differences in front vs rear wheel speed when turning (this prevents binding during turning). Can go all the way to 100% engages (which would be the 50/50 that people talk about).
It is actually not accurate to say 50% of power goes to front and 50% to rear. Even in a fully locked situation, if 3 tires were on ice and 1 tire was on pavement then almost 100% of power would go to the one on the pavement as the other 3 would have no traction and power is defined as force x speed. The 3 with no traction would be generating little force, but spinning at same speed as tire with traction.
I think the rear wheels are engaged period and the clutch controls engagement of the front wheels. I think the tazer forces 2wd by just turning off clutches to front.
If you floor it from standstill, I would expect rear tires to start spinning and almost immediately when wheel speed sensors detect this, the clutch packs would start engaging to transfer power to front wheels. This may happen so quickly that it is imperceptible and feels like all 4 wheels grab immediately. Would be interesting for someone to post slo mo video showing all 4 wheels as jeep is floored from standstill. I don't know how the computer handles side to slide slippage, but suspect it controls this by applying wheel brakes. Differentials are likely open differentials front and back. I think the individual wheel brake method has superceded limited slip differentials in most situations.
One note on transfer case clutch packs..... when they slip the slippage in the clutches creates heat. This can glaze the clutches or overheat transfer case, but is only a concern in really severe situations, like trying to get unstuck (racing engine continuously) or doing donuts for prolonged periods of time. Would not happen unless you were really doing something ridiculous I think.
If you take the time to read the article recommended by "Fast and furious" referenced above, you will see the transfer case is programmed differently for different models. When driving a 392, it is clearly evident that it is not rear wheel drive. Unless you use the Tazer Mini or press and hold the TC button .From wikipedia:
The MP3022 transfer case uses an electronically controlled clutch pack to bias torque from 100% rear to 50/50% front/rear. The transfer case has no center differential, so power can only be supplied to the front axle when the rear wheels begin to slip.
What follows is just my current beliefs. Not gospel truth. I could be wrong, but the only time I've been wrong, was one time when I thought I had made a mistake
My understanding at this point is that rear wheels are engaged all the time and that the clutch is electronically controlled and can go from 0-100% engagement. As it engages it starts transferring power to front shaft, but can still allow slip between front and rear to account for differences in front vs rear wheel speed when turning (this prevents binding during turning). Can go all the way to 100% engages (which would be the 50/50 that people talk about).
It is actually not accurate to say 50% of power goes to front and 50% to rear. Even in a fully locked situation, if 3 tires were on ice and 1 tire was on pavement then almost 100% of power would go to the one on the pavement as the other 3 would have no traction and power is defined as force x speed. The 3 with no traction would be generating little force, but spinning at same speed as tire with traction.
I think the rear wheels are engaged period and the clutch controls engagement of the front wheels. I think the tazer forces 2wd by just turning off clutches to front.
If you floor it from standstill, I would expect rear tires to start spinning and almost immediately when wheel speed sensors detect this, the clutch packs would start engaging to transfer power to front wheels. This may happen so quickly that it is imperceptible and feels like all 4 wheels grab immediately. Would be interesting for someone to post slo mo video showing all 4 wheels as jeep is floored from standstill. I don't know how the computer handles side to slide slippage, but suspect it controls this by applying wheel brakes. Differentials are likely open differentials front and back. I think the individual wheel brake method has superceded limited slip differentials in most situations.
One note on transfer case clutch packs..... when they slip the slippage in the clutches creates heat. This can glaze the clutches or overheat transfer case, but is only a concern in really severe situations, like trying to get unstuck (racing engine continuously) or doing donuts for prolonged periods of time. Would not happen unless you were really doing something ridiculous I think.
Also, when driving in fresh deep snow, (about 8 inches) you can feel the 392 handles differently between the auto mode vs part time mode. "Auto" mode seems to search for the "lane" where the "part time" mode seems to drive with confidence. That is when the transfer case is locked sending power to the rear constantly. I haven't needed to lock the axles yet.
Fast-n-Furious
Well-known member
Just to post some more related resources. WFO concepts made some tweaks (I don’t really understand the mechanism though) to do burnouts and drifting:
And also some details on the front transfer case:
From a recent video (by the end), Trevor claims that the 392’s AWD actually drives really nicely and he could turn it into 2WD using Tazer (with updates?) but the 2WD doesn’t drive that well.
And also some details on the front transfer case:
From a recent video (by the end), Trevor claims that the 392’s AWD actually drives really nicely and he could turn it into 2WD using Tazer (with updates?) but the 2WD doesn’t drive that well.
As for my recent posts, they are from my observations while driving the 392. But since I am Male there is a remote possibility that I can be... incorrect. Lol
Enjoy your 392.
hardhat
Well-known member
I’m just not buying that power is sent to front by default and then to the rear if needed. I think it is other way around. Rear first and then to front of rear spins. Mine will be here in a few weeks and I will find out for sure. Slo mo video will tell the tale I think and if not will be fun anyway.
You may be right though. I just don’t like the thought of default front wheel drive
Forced RWD on the left, normal driving mode on right. Jeep would be coming toward you on the pic. You can see on the right where the front tires grab after slight spin of rear tires.
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I don't like a front wheel drive Jeep either. But I like the 392 jeep.
hardhat
Well-known member
Very cool. On grass, I'm sure you could spin the rears like crazy in forced 2wd. In normal mode, will it spin all 4 on grass or does it pretty much just hook up and go? I guess traction control would probably prevent you from spinning all 4 very much, but would look like a cartoon if you could do it right
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In the forced RWD on the left, it was just a little bump of gas. I gave it a lot more throttle on the right. It really hooks up very quick. On wet pavement it is the same, you can jump off the line with no problem. The power is truly amazing on these Jeeps and the AWD is necessary in my opinion. Don’t get me wrong…I love to show off in 2WD but it needs AWD to drive it daily like it was born to be driven. It’s hard to even take off at a red light when its wet in RWD without spinning.Very cool. On grass, I'm sure you could spin the rears like crazy in forced 2wd. In normal mode, will it spin all 4 on grass or does it pretty much just hook up and go? I guess traction control would probably prevent you from spinning all 4 very much, but would look like a cartoon if you could do it right
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