Larry, are you saying the Wrangler made the difference between first gear and third gear on similar grades? How interesting! My towed car is roughly 2700 lbs on it's dolly.
Keep in mind that it was an 11% grade that put me into first gear. On the way back home, we went DOWN that grade (in 2nd gear, btw) so I can't say what going UP that grade again without the toad would have done. Some hills, I kissed 50 mph and just left it in fourth. Oh, the other thing I did was drain my fresh water tanks, and I know I got rid of 60 gallons (480 pounds). I am saying that shedding the 3,000# Wrangler (or whatever it weighs) and 480# of water, seemed to make a lot of difference. Anyone that has driven a 4106 without a toad knows they scoot along pretty good.
And.....sorry....but I would never stick my wife in the toad on an 11% grade to push the bus, knowing what could happen if anything DID happen. Not saying I wouldn't try it on a more gentle slope, but that seems to me to be a risky move.
When I consider that this was a 41 passenger bus, and that the FAA today calculates each passenger at 170# (ain't THAT a joke?)....we are talking about, maybe 7,000# of PEOPLE load + their baggage and any freight that might be in the bins. My Wrangler represents HALF of the people load and my bins are full of batteries, chairs, outboard motor, genset, grilles, propane tanks, etc. The living quarters may have 600-800# of human waste, maybe the same in grey water, + a half ton of water (8 # per gallon....figger it out), plus clothes, food, big screen TV, couch, bed, dinnette, chairs, etc. I would wager that our most simple conversions might have our coaches sweating like pigs going up some of these grades yanking a toad behind them. JMO.....