4WD auto?

[rmlephiew]

In 4wd auto the truck will not move forward through a turn without applying throttle and if you apply any throttle the rear wheels will begin to skip on the pavement. We tested this on the lot with multiple trucks. Basically put the truck in 4wd auto and try to make a 90 degree or more turn while letting the truck roll forward on its own. My truck will not proceed forward through the turn, but other trucks tested will.

Yep, good description. Mine does the same thing.

 

[riccnick]

For anyone with a binding sensation on dry pavement in 4Auto, I'd bring the truck into the dealer asap and at least have them check and verify the transfer case fluid level. The new t-cases use an electro-mechanical clutch (that I assume is submerged), completely different from the old ball clutch design that nobody liked. This new clutch can, and does, apply some torque even on dry pavement, but if it's applying too much, and won't scrub in order to allow the wheels to not bind, there's an issue there for sure. I'd also make sure you have all of the RRT powertrain updates as well, regardless of Hemi or eTorque powerplant, as the transfer case logic could be buried in there too.

 

[stevj]

Copied from the FSM:
"
21 - Transmission and Transfer Case / Transfer Case, BW48-11 / Description
DESCRIPTION AND OPERATION
DESCRIPTION
This is an electronically controlled active full-time transfer case.
A wet clutch in the transfer case is used to control torque transfer to the front and rear axles. A low range gear reduction system provides increased low speed torque capability for off road operation. The low range provides a 2.64:1 reduction ratio.
OPERATION
The input gear is splined to the transmission output shaft. The input gear drives the mainshaft through the planetary assembly and range sleeve. The front output shaft is operated by a drive chain that connects the shaft to a drive sprocket on the mainshaft. Depending on traction conditions, the Drive Train Control Module (DTCM) will modulate the electromagnetic clutch assembly to vary the amount of torque applied to the front axle. Torque is transmitted through the input shaft to the clutch and drive sprocket assembly, and is transferred directly to the rear propeller shaft, and to the output shaft and front propeller shaft by the drive chain. The oil pump circulates gear lube throughout the case to provide clutch cooling.
OPERATING RANGES
The operating ranges are:

• 2HI.
• 4WD Auto.
• 4WD Lock.
• Neutral.
• 4WD Low

The 4WD Auto mode can be used at any time and on any road surface.
"

Steve

 

[HKP7PSP]

For anyone with a binding sensation on dry pavement in 4Auto, I'd bring the truck into the dealer asap and at least have them check and verify the transfer case fluid level. The new t-cases use an electro-mechanical clutch (that I assume is submerged), completely different from the old ball clutch design that nobody liked. This new clutch can, and does, apply some torque even on dry pavement, but if it's applying too much, and won't scrub in order to allow the wheels to not bind, there's an issue there for sure. I'd also make sure you have all of the RRT powertrain updates as well, regardless of Hemi or eTorque powerplant, as the transfer case logic could be buried in there too.

Sound advice. I have a slight bit of whirring noise on acceleration and turns when using 4WD Auto. I checked the transfer case this evening, and it is definitely full. So I will probably write it off as normal noise for this unit. It definitely drives like it's always engaged - I get no wheelspin when doing full throttle acceleration from a stop in 4Auto unlike 2WD.

 

[zenithgarfunkel]

I have my truck back, but we are waiting on a software update from FCA that addresses the issue. It sounds like the manufacturer is aware of this issue and is working on an update to hopefully fix it.

 

[HKP7PSP]

I have my truck back, but we are waiting on a software update from FCA that addresses the issue. It sounds like the manufacturer is aware of this issue and is working on an update to hopefully fix it.

I had to go back and read your symptoms and that sounded pretty bad. Mine doesn't bind on turns, and definitely will idle through a turn from a stop, so I don't believe that's what I'm having. Mine will make the whirring noise on turns (it's far louder if you put it in 4Hi and do the same thing) and sometimes on light acceleration. I checked the fluid in the x-fer case and it is full.

The noise is annoying, but binding is definitely no good. What did your dealer say about the software aspect if you don't mind me asking?

 

[zenithgarfunkel]

I had to go back and read your symptoms and that sounded pretty bad. Mine doesn't bind on turns, and definitely will idle through a turn from a stop, so I don't believe that's what I'm having. Mine will make the whirring noise on turns (it's far louder if you put it in 4Hi and do the same thing) and sometimes on light acceleration. I checked the fluid in the x-fer case and it is full.

The noise is annoying, but binding is definitely no good. What did your dealer say about the software aspect if you don't mind me asking?

The technicians contacted STAR and STAR said they were aware of the binding issue and were working on an update to address it. I didn’t get an ETA, just that it would be released soon. I’ll need to take it back in once it is released. I was advised not to use 4wd auto for now.

 

[riccnick]

Sound advice. I have a slight bit of whirring noise on acceleration and turns when using 4WD Auto. I checked the transfer case this evening, and it is definitely full. So I will probably write it off as normal noise for this unit. It definitely drives like it's always engaged - I get no wheelspin when doing full throttle acceleration from a stop in 4Auto unlike 2WD.

Thinking more on this, the front axle engagement could be the whirring noise as well, if you can, I'd check the front diff fluid level too.

Sad to think we all have to go running around checking factory fill levels, but the dealership found my transmission "1 quart" low on fluid when I brought it in for the 10,000 mile service

 

[HKP7PSP]

Thinking more on this, the front axle engagement could be the whirring noise as well, if you can, I'd check the front diff fluid level too.

Sad to think we all have to go running around checking factory fill levels, but the dealership found my transmission "1 quart" low on fluid when I brought it in for the 10,000 mile service

I will do that. How do they check the transmission level? I thought they were sealed for life - I haven't seen a dipstick anywhere for it.

Edit: checked front diff. Has fluid in it, I can put my pinky in and bend downward to feel it. Not sure how full it needs to be.

 

[Andoskyy]

The technicians contacted STAR and STAR said they were aware of the binding issue and were working on an update to address it. I didn’t get an ETA, just that it would be released soon. I’ll need to take it back in once it is released. I was advised not to use 4wd auto for now.

Have you heard from the dealer on the potential update?

I'm having this issue as well but was going to wait to go to the dealer

 

[Thewrangler73]

I put mine in auto anytime its anything other than dry. Some peopel may disagree, but thats what i do.

I had mine in 4wd auto and was told by dealer after transfer case overheated that you should only use it on gravel or lighly muddy roads. Was I given bad info?

 

[392DCGC]

I had mine in 4wd auto and was told by dealer after transfer case overheated that you should only use it on gravel or lighly muddy roads. Was I given bad info?

I would show the dealer the manual where it states "any time and on any surface" and tell them to get a clue.

 

[HKP7PSP]

I have mixed feelings on 4WD Auto. I don't think it's truly good to use on dry, hard surfaces - but on the other hand, the manual says it's okay to do full time. Yes, it does allow slip so as to not bind / wind up your system when turning and such like you'd experience with 4 High... but at the same time, I can hear and feel that it's under strain when being used on pavement. On 4 high, it is much more locked feeling in regards to binding and noise, so I know it's working properly in Auto. My dealer said the system is acting as normal, and this is now documented in the vehicle history, so time will tell.

 

[zenithgarfunkel]

Have you heard from the dealer on the potential update?

I'm having this issue as well but was going to wait to go to the dealer

I have mixed feelings on 4WD Auto. I don't think it's truly good to use on dry, hard surfaces - but on the other hand, the manual says it's okay to do full time. Yes, it does allow slip so as to not bind / wind up your system when turning and such like you'd experience with 4 High... but at the same time, I can hear and feel that it's under strain when being used on pavement. On 4 high, it is much more locked feeling in regards to binding and noise, so I know it's working properly in Auto. My dealer said the system is acting as normal, and this is now documented in the vehicle history, so time will tell.

There has been no update as of about one week ago. As others have mentioned the manual states that 4WD auto can be used all the time. There was no noticeable difference between 2WD and 4WD auto on another truck we drove to compare to mine. My truck will not idle through a turn in 4WD auto.

 

[Joker4L]

I noticed to get 1mpg better when in 4WD Auto. It baffles me because I should be getting better MPG with 2WD. I test 2 whole tanks back to back on 2WD and 2 whole tanks back to back on 4WD auto on the same exhaust commute. I average around 16.8 with 4WD AUTO and 15.5MPG with 2WD.

 

[HKP7PSP]

There has been no update as of about one week ago. As others have mentioned the manual states that 4WD auto can be used all the time. There was no noticeable difference between 2WD and 4WD auto on another truck we drove to compare to mine. My truck will not idle through a turn in 4WD auto.

Interesting. On mine, 4Auto is definitely different from regular 2WD, namely, it won't turn as tightly and you can hear the mechanical differential noise as you turn, but you can idle through the turn no problem, even while on the brakes. With this transfer case and front differential, in 4Auto it does fully engage the front at all times, but won't send much power to the front until needed (split second, you likely won't even get wheelspin), so it's interesting that you noticed no difference between 2WD and 4Auto with other trucks.

 

[HeliPilot]

Interesting. On mine, 4Auto is definitely different from regular 2WD, namely, it won't turn as tightly and you can hear the mechanical differential noise as you turn, but you can idle through the turn no problem, even while on the brakes. With this transfer case and front differential, in 4Auto it does fully engage the front at all times, but won't send much power to the front until needed (split second, you likely won't even get wheelspin), so it's interesting that you noticed no difference between 2WD and 4Auto with other trucks.

I think he means that the other trucks he drove did not bind and hop (as if it were in 4HI on dry pavement) like his does in 4auto

 

[zenithgarfunkel]

I have a question for everyone. My truck is supposed to have the limited slip rear differential. With this differential should it even be possible for the rear axle to lock? What’s happening with my truck seems to be similar to what would happen if it had the locker differential and it were locked. Anytime I engage any 4WD mode it seems like the rear differential locks so that the rear wheels can’t turn at different speeds.

 

[Gman]

That would indicate a problem with the Anti-Spin mechanism. It should only lock when one tire slips and should also automatically release.

 

[riccnick]

I have a question for everyone. My truck is supposed to have the limited slip rear differential. With this differential should it even be possible for the rear axle to lock? What’s happening with my truck seems to be similar to what would happen if it had the locker differential and it were locked. Anytime I engage any 4WD mode it seems like the rear differential locks so that the rear wheels can’t turn at different speeds.

Regardless of whether the truck is equipped with a limited slip diff or not, you will get scrub, or wheel hop, on dry surfaces when turning in 4wd. However, in 4Auto, you should not get any scrub or wheel hop on dry pavement IF the truck is not detecting any wheelspin. If you are repeatedly getting scrub or wheel hop in 4Auto, you should definitely bring it to the dealership asap. I would have them check to make sure all the latest powertrain flashes are installed, and also check the transfer case fluid level.