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2016 ATS4 2.0T
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75 Posts
Discussion Starter #1
I've searched and haven't been able to find anything definitive that describes the ATS AWD system. Does anyone have any links or info about the mechanics of how it actually operates in various conditions? IE, whats the power split in normal conditions, does it change front/rear bias under slippage, what conditions cause it to change, etc.). Even the specific type of transmission, and if it's used in other Cadillacs or other cars in general. I'd appreciate any info you have!
 

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2014 ATS 3.6L AWD Performance
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429 Posts
I got the following from another ATS owner in the FB group, who's a mechanic with an AllData subscription. When he looks up his 2014 2.0T AWD, he found:

Transfer Case Description and Operation
The Borg Warner (BW) model 4474, transfer case is a 1-speed active design.

The BW 4474 transfer case allows vehicle speed dependent flexible clutch preload torque levels for enhanced system performance. An on-demand torque biasing friction clutch is tuned through software calibrations. When a driver enters a turn, clutch torque is decreased based on the various CAN inputs, such as steering angle, to prevent crowhop or driveline binding from occurring at low speeds. If the driver were to accelerate hard enough in a turn to induce rear wheel slip the transfer case would immediately correct it and then reduce torque to prevent crowhop or binding.

The system is fully automatic, requires no driver intervention, and has its own control module integrated with the vehicle chassis control system via the vehicle's CAN bus. The torque split between the front and rear axle is not fixed as in an open center differential transfer case meaning the active transfer case has the ability to transfer up to 100% of available torque to the front axle as needed.

The case halves are die-cast aluminum. Ball bearings support the input shaft and front output gear. Tapered bearings support the idler gear. Power from the input shaft is transferred to the front output shaft via a helical gear set. A gerotor type oil pump is driven by a shaft located into the end of the idler gear assembly. Oil is pulled from the sump through the filter and screen, pumped through the oil distribution hub, and into the input shaft oil gallery for the clutch and bearing lubrication.

Torque is transferred to the front axle through an active wet clutch within the transfer case. The clutch pack is engaged by an electromagnetic clutch coil and ball ramp assembly. By varying the amount of current, torque output to the front axle can be adjusted.

Whenever the coil is energized as determined by vehicle operating conditions and commanded by TCCM, the armature in the clutch housing is magnetically drawn toward the rotor. Torque is generated through friction between the armature and rotor. Friction torque is multiplied through the ball cam mechanism and applied to the clutch pack. The clutch pack assembly contains a predetermined selectable pressure plate, friction, and reaction plates that are to be serviced as a clutch pack assembly. Clutch activation is controlled by a pulse width modulated voltage signal. If the clutch pack assembly is replaced, the TCCM must be recalibrated using the service calibration.
Borg Warner video about their Torque-On-Demand transfer case...

Due to the the electromagnetic clutch, you can safely run in RWD by pulling the #31 fuse (double-check the # before you do it!) and not risk damaging the hardware. The default torque bias would seem to be 100% rear, and without power to the clutch, FWD is effectively disengaged with no ongoing slippage. Thinking about it another way, if there were an electrical fault in the transfer case, you would still have mechanically-connected RWD and remain mobile.

Based on some quick research, the AWD CTS shares the same transfer case going back to the 2nd-gen model. It seems that the BW4474 has been around awhile, as I've found references to it being used in the AWD Astro vans as well as the Syclone/Typhoon, Olds Bravada, and very likely the Hummer H3 - to name a few...guessing it's a pretty durable and reliable. 馃槈
 

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2016 ATS4 2.0T
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75 Posts
Discussion Starter #3
This is good info, thanks! I've seen a few people do the fuse modification here, so that all seems to make sense. Interesting that it seems to be 100% rear-bias. I wonder if that means turning off TC in the winter would be mostly RWD behaviour then.
 

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2014 ATS 3.6L AWD Performance
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429 Posts
This is good info, thanks! I've seen a few people do the fuse modification here, so that all seems to make sense. Interesting that it seems to be 100% rear-bias. I wonder if that means turning off TC in the winter would be mostly RWD behaviour then.
If I understand correctly, the TC system (as well as driving modes) and the transfer case operation are independent of each other. Torque will still transfer to the front based on slippage at the rear. So yes, you'll be able to get the rear to step out, RWD-style, in the winter, but with the front also coming into play, AWD doughnuts are...'different'.

ATS example... CTS AWD example (same transfer case) ... Now get out there and find somewhere to play! :giggle:
 
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