That's impressive.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

Found this "The Ram 1500 TRX uses a BorgWarner 48-13 full-time active transfer case with a 2.64:1 low range"

from here: https://www.caranddriver.com/news/g33616182/2021-r...

I haven't found specifications on the 48-13 but here's the 48-12: https://www.borgwarner.com/newsroom/press-releases...

And then I found this: https://www.youtube.com/watch?v=QWiFl9K3WqI

And that reveals that there is no center diff at all ... just a multiplate clutch with clamping pressure that can be modulated to regulate torque delivery to the front axle.

The video doesn't show it, but there will be a single planetary gearset to provide the 2.64:1 low range function. Input shaft goes to the sun gear always, outputs to both the rear axle and that above-mentioned clutch pack come from the planet carrier, and the ring gear either locks to the case to provide low range or locks to the planet carrier to provide high range.

Perhaps they've got a diff to give the 50/50 and then just slip a clutch for the other splits?

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

Thanks for the replies. Greg I think the 50/50 split only applies to the low range, and was not listed for the high range options. Brian, your 2nd link from BW seems to describe the same clutch system for the previous year's T-Case, as well as the new one, both appear to be Electro-Mechanical On-Demand (EMOD). This uses a motor driven cam to vary clamping force on the clutch pack. But how can they be so precise on the splits, like 40/60 and 45/55 ?

The previous Ram's T-Case design was Torque on-Demand (TOD), described here in the video: Link

... which was similar to the "center coupling" on the Mazdaspeed6, described in detail here:
Link Pgs 38-40.

Thanks again!

They can't be that precise on the torque splitting - and they aren't, and won't be.

In particular, if you are rounding a sharp corner, the front wheels will carve a longer trajectory than the rear, and it will not be possible to transmit any forward torque to the front drivetrain at all (any engagement of this clutch will try to drag the front wheels and drive the rears).

... unless you are spinning the rear tires while rounding the corner ... then beyond a certain slip percentage, it will start to be able to drive the fronts.

Good point Brian, that's why I thought sets of planetary gears would be used. On the Mazdaspeed6 I had linked, pulse width modulation is used for loading the pre-clutch, giving the F&R the ability to take curves that would not be possible with a DC load on the magnet. But the split is variable, just enough to prevent rear tire spin in that FWD based application. It has high rear bias taking off hard from a stop. On the Ram, perhaps the "motor and cam" loaded clutch also used PWM to preload the clutch, and the pulse width is based on 4WD dyno runs with the load bias related to a specified split.

I helped this guy with his Mazdaspeed6 suspension, and that center coupling with PWM had no problem with tight corners in the SCCA solo 1 Nationals:
Link

I don't know anything about this truck but Borg warner makes the transfer cases for the Land Rovers and they use an elecro-hydraulic torque control for their AWD's since 2017. I believe it's continuously variable though? This seems to by a hybrid of that transfer case.