Traction MFWD-Does it lock rear diff?

Rmd8136 · Feb 21, 2016

Does the design of the MFWD engagement also lock the rear diff? Or must you use the foot operated diff lock pedal at same time to get 4 driven wheels?

jenkinsph · Feb 21, 2016

The engagement of the differential lock is separate from the mfwd engagement. With good reason, when the differential lock is engaged steering is dramatically reduced as the rear wheels want to go in a straight line.

Rmd8136 · Feb 21, 2016

That is what I thought. When trying to pull up a stump with chains, I am almost positive I have seen both rear wheels spinning w/o depressing the diff lock pedal. Is that possible? I would think not as I assume the rear diff is "open" and powers the wheel with least traction. But I am not sure. How is power determined to go to a rear wheel w/o diff lock engaged? Also, both front wheels are driven with MFWD engaged? Correct?

Rmd8136 · Feb 21, 2016

Perhaps the rear diff is mechanical limited slip?

k0ua · Feb 21, 2016

Rmd8136 said:
That is what I thought. When trying to pull up a stump with chains, I am almost positive I have seen both rear wheels spinning w/o depressing the diff lock pedal. Is that possible? I would think not as I assume the rear diff is "open" and powers the wheel with least traction. But I am not sure. How is power determined to go to a rear wheel w/o diff lock engaged? Also, both front wheels are driven with MFWD engaged? Correct?

It is easily possible that both rear wheels can spin without them being locked by the differential lock. If tractive forces, are equal both rear wheels will spin. Study how an open differential works, and it will answer your questions. One of the best ways to help with this is an old GM instructional video.

k0ua · Feb 21, 2016

Rmd8136 said:
Perhaps the rear diff is mechanical limited slip?

Not likely. You do not have to have Limited slip. If tractive forces are equal an open differential will pull equally.

beenthere · Feb 21, 2016

Rmd8136 said:
That is what I thought. When trying to pull up a stump with chains, I am almost positive I have seen both rear wheels spinning w/o depressing the diff lock pedal. Is that possible? I would think not as I assume the rear diff is "open" and powers the wheel with least traction. But I am not sure. How is power determined to go to a rear wheel w/o diff lock engaged? Also, both front wheels are driven with MFWD engaged? Correct?

Both will have power as long as both get traction. When one breaks free, then the other one will spin twice as fast. Some control by braking the one side that spins will get more traction. That is good use of the steering brakes. Can't do that on those hst tractors that have the individual steering brakes on the same side as the forward reverse pedals.

Answered well by previous post.

RickB · Feb 21, 2016

beenthere said:
Both will have power as long as both get traction. When one breaks free, then the other one will spin twice as fast. Some control by braking the one side that spins will get more traction. That is good use of the steering brakes. Can't do that on those hst tractors that have the individual steering brakes on the same side as the forward reverse pedals.

Answered well by previous post.

When one wheel breaks free it spins, not the opposite wheel.

beenthere · Feb 21, 2016

RickB said:
When one wheel breaks free it spins, not the opposite wheel.

Correct.. my bad.. should have said "breaks free and spins twice as fast"

RedNeckRacin · Feb 22, 2016

Some of the larger tractors have a limited slip in the front axle. The rear axle is full lock or unlocked with the foot pedal usually. My Deere has limited slip in the front axle and differential lock in the rear, my kubota has an open diff in the front and a diff lock in the rear. Both have to be manually put in 4wd.