4 wheel drive class c

j-d wrote:
BECAUSE IT'S AN "OPEN DIFFERENTIAL" SO THE WHEEL WITH THE POOREST TRACTION WILL BE THE ONE TO SPIN. NO DIFFERENT THAN IF YOU JACKED ONE WHEEL, PUT IT IN DRIVE AND GAVE IT THE GAS. THE WHEEL YOU LIFTED WOULD SPIN.

Sorry .... but that is not right from the rear axle end of the drive train ... only from the engine end of the drive train.

Through an open differential in an unequal rear tire traction situation, the engine will indeed try to spin the easiest to spin tire ... as you say.

Jacking up one rear wheel so it has "no traction" and then having the other rear wheel turn on the ground when the vehicle tends to move off the jack ... cannot happen without the driveshaft getting torqued by the turning tire on the ground ... but the driveshaft cannot turn (much - see below) because it will be locked by the transmission mounted drum emergency brake and/or the park gear.

Now, there can possibly be enough "slop" in the overall driveshaft/emergency brake/park gear system so as to allow the jack to maybe tip over or start to tip over. I agree on this. With an emergency brake right on each wheel, this tip of the jack would not happen (unless the tire on the ground slips on the ground surface) . This is why I block both sides of the tire on the ground whenever I jack up the other side - whether it be in the front or back.

Of course in at least the last several decades Ford would not dare sell a vehicle that could roll off a jack when the other tire was on the ground - due to a person not being able to somehow lock the drive system connected to the non-jacked tire (discounting gear slop).

FWIW, the motorhome we owned before our current one came stock from GMC without a park gear in it's automatic transmission. It only had some kind of emergency brake. What a high stress design this was.