Why huge differentials on trucks?

[LouNY]

I believe that most people would be amazed at how small flimsy looking so many gears are
in transmissions and other locations.
I know the first time I ever saw the cover off a tractor (Farmall 560) I could not believe how small the gears were.
Thin and not very robust looking for the transmission and differential, then you got to the pinion gear that was much more as to what would be expected in a tractor, then the bull gear, that was a gear.
And then to see the design that went into those older drivetrains, simple seeming 5 speed trans with a single reverse, then a mechanical disc type brake mounted on the pinion shaft so that the braking force was multiplied by the pinion / bull gar ratio just as the power was.

 

[Industrial Toys]

Maybe the Gears in my Childhood Meccano set would dwarf those in a HONDA. lol

 

[oosik]

Ahhh.....OVRSZD, that is exactly what my Owners Manual says. I really don't think there will be many times that I'm in 4LO and need to lock both front & rear differentials. At that point a person had better be looking for a friend with a large vehicle or a good dead man. Either to act as a winch point.

From over twenty years of off-roading in AK - perspective is superior to charging forward. In a tough situation, my Taco Wagon @ 7540# could be a tough pull. Lower gears & higher HP are little comfort when the mud is coming in over the window ledge on the drivers door.

Besides - when the vehicle is that deep in the mud - it is NO FUN diving down to get the hook on the end of the winch cable.

 

[RalphVa]

I figured it out. It's the size of the gears, and those Subaru, Benz and Miata differentials aren't so small. First, with more power/torque input, you need to have bigger teeth or to go to higher strength steel. Bigger teeth = bigger ring gears. The Subaru, Benz and Miata differentials appear small because you only see the lower ends of them. The ring gear is there, with smaller teeth than on a truck or pickup, but is mostly above the shaft input from the transmission.

Ralph

 

[masscity]

In the mid 90's we were pouring a basement wall. A rear dumper, a Mack I think was heading to the back of the job in granny gear in peanut butter mud.

There's a big boom and oil spilling out of the transfer case. Dead in the water, I had to bucket the 11 yards so they could tow it back to their yard.

Watching Graveyard Cars, all the Hemi's and maybe the 440 six pack got a Dana 60 in them.