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title seems simple but please let me elaborate. i know 4matic drives all 4 wheels however is it all the time? or on demand? i feel it's the latter which i will explain next. what's the answer? and how does it work?
I ask bc recently i was working on the car and had the rear end raised (both rear wheels off the ground). i was on an inclined driveway with the front end facing up the incline, and i placed chocks on the front wheels.
once done with my work, i remove the jackstands and left the jack on the rear diff with the rear end still in the air. i hastily removed the front wheel chocks and to my surprise the car started to slide down the driveway! thankfully i did not panic and threw the chocks back on to halt everything. then i started scratching my head...
i would think the 4matic driveline would go from the front wheels all they way to the trans which was in park and stop the rolling but it did not - which lead me to believe the front transfer case was open/disconnected. is there a clutch in the transfer case that engages when traction is needed? sorry if this topic is elementary...i thought i understood AWD systems but clearly i do not .
Last edited by timmy0tool; Oct 15, 2025 at 05:56 PM.
I'm curious about this too, as I have also been confused before about why wheels were or were not spinning freely when I've had my various 4matic vehicles (I've owned three) up on jackstands. I did a little research, and depending on the state of the differentials, the front wheels may or may not spin freely. Putting the transmission in Park locks the driveshaft, but not the differentials. If the front differential is open (not engaged) then the front wheels can still spin.
Parking pawl is inside the transmission, and t-case after that. Driveshafts are naturally connected to a t-case. Inside of a t-case is planetary gearset that splits torque 45/55 (or 40/60, depends on source), so the car is rear wheel biased.
Found an exploded view of the t-case from the nemigparts website, and it looks like there's nothing special in there, just mechanical gears.
Planerary gears allow speed difference between the front and rear axle so there's no binding in driveline, which would happen with the part-time t-case on dry pavement
So like on the OP's case, rear wheels off the ground and fronts chocks removed, there's nothing stopping the front driveshaft turning, even if the parking brake is applied on the rear wheels. Differential limited slip or locker does nothing in this situation. On a normal driving, ABS and ESP take care of the control. T-case just splits the torque, nothing more
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Which specific transmission 722.6xx or 722.9xx? 722.6 has separate transfer case and the 722.9 has the integrated transfer case which doesnt really matter for the rolling issue but they are different with power output to front/rear.
I am far from an expert on transmissions though from my understanding the front/rear should not be able to roll in a 4matic 722.6 or 722.9. There is a parking pawl at the back of the transmission that locks the output shaft that connects to the transfer case. It should prevent the front driveshaft and the rear drive shafts from rotating.
For the 722.6 4matic it mentions a fixed drive torque of 40% front/ 60% rear. So im assuming that means both front and rear are fixed to the output shaft. Cant imagine the front drive shaft being able to rotate freely.
Not sure how you can test if the parking pawl is functioning properly other than if the car rolls away when in park.
I have a 4matic and when I drive it up on ramps i'll put it in park and it seems to roll a little then stops. Then i'll set the e-brake. This way I know its in park and the transmission will hopefully keep it from rolling. I've had just the rear jacked up many times and never noticed any rolling in the front.
722.9 transfer case:
722.6 Transfer case:
Parking pawl similar on both transmissions:
Heres a 722.9 4matic transmission. Can see the parking pawl (1). Transfer case is not shown.
I am far from an expert on transmissions though from my understanding the front/rear should not be able to roll in a 4matic 722.6 or 722.9. There is a parking pawl at the back of the transmission that locks the output shaft that connects to the transfer case. It should prevent the front driveshaft and the rear drive shafts from rotating.
Yes, this is correct when the vehicle stands on all four tires on the ground.
Originally Posted by TimC300
For the 722.6 4matic it mentions a fixed drive torque of 40% front/ 60% rear. So im assuming that means both front and rear are fixed to the output shaft. Cant imagine the front drive shaft being able to rotate freely.
Fixed, meaning the split stays the same 40/60 regardless of the conditions or control, as there are only mechanical gears. If there were a clutch pack, it could be variable like on Subaru, where it can go from 35/65 to 50/50.
Originally Posted by TimC300
Not sure how you can test if the parking pawl is functioning properly other than if the car rolls away when in park.
I have a 4matic and when I drive it up on ramps i'll put it in park and it seems to roll a little then stops. Then i'll set the e-brake. This way I know its in park and the transmission will hopefully keep it from rolling. I've had just the rear jacked up many times and never noticed any rolling in the front.
E-brake is the magic word.
You can test the pawl even on a level ground, put the shifter on park and push the vehicle. Incline would make this little easier.
But on a incline, it's recommended to first apply parking brake, the shift to park. Other way around it strains the transmission unnecessarily.
I once parked 3/4 ton pick-up against the curb so the rear wheel had gone slightly up, I shifted to park and let the foot brake loose. Truck rolled forward jamming the pawl, and I had to use some force to get it out of park, when it let go there was a huge bang but nothing broke.
Originally Posted by TimC300
722.9 transfer case:
When we look at the above picture, green part is output shaft, and let's pretend it's in park, so it doesn't turn. And rear wheels off the ground, no parking brake applied.
Output is connected to the ring gear, so it doesn't move, either.
Blue part of the planetary set is a carrier, that supports the planetary gears (also blue). No parking brake, wheels off the ground, you can turn the wheels and output, as the planetary gears turn against the fixed (trans in park) ring gear.
Yellow part is connected to a front axle, and has a sun gear. This also can turn because the planetary gears turn because the carrier turns with the rear.
I incorrectly stated earlier that front would turn even when the parking brake is applied. Applied parking brake equals situation where all tires touch the gound.
Yellow part is connected to a front axle, and has a sun gear. This also can turn because the planetary gears turn because the carrier turns with the rear.
i think this best answers my question, after reading the entire post a few times! thank you everyone especially @TimC300 for the detailed reply!
my parking brake isn't the best and i noticed every time i engage it, the car still rolls back and stops at the parking pawl anyway - thus the phenomenon i experienced!
Last edited by timmy0tool; Oct 29, 2025 at 09:04 PM.
i think this best answers my question, after reading the entire post a few times! thank you everyone especially @TimC300 for the detailed reply!
my parking brake isn't the best and i noticed every time i engage it, the car still rolls back and stops at the parking pawl anyway - thus the phenomenon i experienced!
I try not to even use my parking brake anymore, afraid it will rust weld the pads to the rotor, especially if it gets wet.
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