Posi-Traction?

sald · Sep 23, 2018

I was backing my 1940 Farmall A up a wet soiled grass hill and halfway up my right wheel lost traction and just was spinning, the left didn't move and I essentially stopped moving. In reverse is there only traction to one wheel while in forward gears both?
Every time I play I have more questions, figure this is the place for them...

rustyfarmall · Sep 23, 2018

No difference between reverse or forward. When one wheel loses traction, apply the brake on that side. Power will then be transferred to the other wheel.

Traction is usually greater when moving forward because of how the tires are designed, but on wet grass, all bets are off.

old · Sep 23, 2018

Most tractor are like most cars and truck and if you loose traction on one tire they will just sit and spin that tire. That is one reason a tractor has left and right hand brakes so if traction is a problem one might be able to keep moving by hitting the brake on the side that starts spinning

sald · Sep 23, 2018

Thanks guys. Glad I asked.

Brendon-KS · Sep 23, 2018

With the standard open differential both wheels are always contributing equally to moving, or at
least attempting to move, the vehicle. The direction of travel doesn't make any difference.
Whichever wheel loses traction first dictates the amount of tractive effort that each wheel will be
applying to the ground, regardless of whether or not that amount of force is enough to move the
vehicle. Although one wheel might be setting motionless it is still pushing on the ground just as
hard as the wheel that is spinning. The sight of one wheel spinning and the other setting still
has lead to the myth that an open differential only drives one wheel.

used red MN · Sep 23, 2018

Watch this video, same thing in your tractor. When that happens step on the brake of the wheel that is spinning this will force the differential to send more torque to the opposite wheel that has more traction. This will help you move through a slippery spot. Be prepared to disengage the clutch incase the tractor does not react as intended. Also due to the angle of the traction bars on normal ag tires they generally have less traction in reverse then forward due to the cleaning action as the bars slip. This difference is not real noticeable on slick grass more so in loose soil, mud or snow.
Differential animation

sald · Sep 23, 2018

Thats a great video. I actually bookmarked this one when I was explaining to my 9 year old son. It made me remember the old books my father used when he explained it to me years ago (he is 82 and was a mechanic for his career). Thanks for the help!

https://www.youtube.com/watch?v=K4JhruinbWc

Janicholson · Sep 23, 2018

One more comment. When backing up a hill, the weight is lessened on the rear wheels. When driving
forward up a hill, the traction is increased on the rear wheels. It is a big difference. Jim

Posi-Traction?

sald

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rustyfarmall

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old

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sald

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Brendon-KS

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used red MN

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sald

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Janicholson

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