Operating tractor in 4wd all the time?

[tradosaurus]

Bringing a discussion from a Kubota thread here.

I've heard different opinions on operating a tractor in 4wd. My last L3301 which I only racked 91 hrs before selling I kept the 4wd engaged all the time. 100% of my work was on dirt or grass.

I'm curious what of others opinions and practices.

One forum a person stated

On many CUTs and SCUTs, it's very different from automobiles. The only brake is in the transmission, not on the wheels. So it is generally advised to keep the tractor in 4WD whenever operating the FEL or any other front implement that could make the rear wheels light, especially on hilly terrain.

If in 2WD and the rear wheels get light due to insufficient ballast, or bouncy conditions, or a steep downhill, the tractor can lose all braking ability both from the hydro transmission and the brakes, due to loss of traction. In 2WD, there will be no braking ability with the front wheels -- they will free-wheel.

 

[tomplum]

My front axle is engaged ~80% of the time. Dealing with slopes, creek flats and loader work is the main use of our tractor. When I can I'll slide it back into 2WD. I changed my front axle oil at 200 hours rather than the 500? hours in the manual thinking it would be good to be proactive. Very minimal particulate.

 

[old and tired]

The post you posted is correct. R4 industrial tires are horrible at traction in anything OTHER than pavement. I don't have pavement and keep my tractor in 4x4 all the time.

If it causes any problems, I'll gladly pay that repair bill IF or when it comes. I've been in a couple uncontrolled slides and don't plan to do another one....

 

[rScotty]

There shouldn't be any debate about this. Tractors aren't AWD (all wheel drive), they are 4WD. The difference is basically that 4WD machines have a shiftable front drive assist because they lack a differential in the shaft that goes from the transmission to drive the front axle.

Since they don't have that differential, they can build up torsional stress in the front drive shaft and transmission. They avoid that torsional stress in the couplings and shafts by slipping a tire now and again. To slip a tire, they need to be on a surface that allows for some front tire slippage - just a little bit of slip now and then will do it. So with R4 industrial tires on dirt and grass surfaces you should be fine.

Just remember to shift into 2WD when on a high traction surface like asphalt.

As you say, our problem comes when carrying a heavy load in the FEL and going downhill. You clearly want to be in 4WD to prevent the uncontrolled slide, but in 4WD that full bucket right over the front tires keeps them from slipping just when they need to do so to protect the tractor running gear. So the solution is a compromise - either carry less load in the bucket or back down. Or risk a slide. -

I've got some steep sections where uncontrolled slides are a possibility - in fact one area is right on my driveway where I need to carry loads in the FEL. I've got r4s and have slid there several times - both in the snow and also in the summer when the dirt is hard packed and dry, so I know just what you are facing. This with many tractors over 50 years.....

As far as I know, there isn't a real good solution. Using Ag tires helps prevent the slide in snow, but is way worse on dry hard dirt. So I think R4s are still the best tire for that. Someday our tractors will have AWD -All Wheel Drive - with a center differential and brakes on the front wheels like the European tractors have. After all, most cars and trucks are built that way now. That will solve the problem.
rScotty

 

[Henro]

There shouldn't be any debate about this. Tractors aren't AWD (all wheel drive), they are 4WD. The difference is basically that 4WD machines have a shiftable front drive assist because they lack a differential in the shaft that goes from the transmission to drive the front axle.

Since they don't have that differential, they can build up torsional stress in the front drive shaft and transmission. They avoid that torsional stress in the couplings and shafts by slipping a tire now and again. To slip a tire, they need to be on a surface that allows for some front tire slippage - just a little bit of slip now and then will do it. So with R4 industrial tires on dirt and grass surfaces you should be fine.

Just remember to shift into 2WD when on a high traction surface like asphalt.

As you say, our problem comes when carrying a heavy load in the FEL and going downhill. You clearly want to be in 4WD to prevent the uncontrolled slide, but in 4WD that full bucket right over the front tires keeps them from slipping just when they need to do so to protect the tractor running gear. So the solution is a compromise - either carry less load in the bucket or back down. Or risk a slide. -

I've got some steep sections where uncontrolled slides are a possibility - in fact one area is right on my driveway where I need to carry loads in the FEL. I've got r4s and have slid there several times - both in the snow and also in the summer when the dirt is hard packed and dry, so I know just what you are facing. This with many tractors over 50 years.....

As far as I know, there isn't a real good solution. Using Ag tires helps prevent the slide in snow, but is way worse on dry hard dirt. So I think R4s are still the best tire for that. Someday our tractors will have AWD -All Wheel Drive - with a center differential and brakes on the front wheels like the European tractors have. After all, most cars and trucks are built that way now. That will solve the problem.
rScotty

rScotty, that was a lot of verbiage to say simply if you are operating in 4WD all the time on dirt/grass you probably do not have to worry! LOL

 

[Rustyiron]

As long as the internal "tension" from turning (shorter path of the rear axle) can be released with some wheel slip on a giving surface, your good.
rscotty said this above, just a little longer and more technical.

 

[kthompson]

I have a B2710 and I can feel it binding if used on surface the front wheels can not slip on. But not having real slopes here to worry about slipping going down have a question on that: If the slope is that slick or smooth and you are carrying a heavy bucket load, are you not also getting some slippage with the rear wheels or to me slipping would not be a concern.

 

[rScotty]

An old 2710....well it must be getting on to twenty years old now. Does it still work well? It wouldn't surprise me to hear that it works pretty much good as new.....It's hard to beat those old ones.

I'd say you are right about the rear slippage. The shafts and couplings forward of the transmission leading to and also in the front axle are smaller in diameter (and higher in internal ratio) than the rear drive system, so the front end parts suffer most of the torsional wind up.

But for releasing that windup it doesn't matter if you slip the front tires or the rear tires. It's just like winding up a rubber band, it will untwist from either end.

Remember those balsa wood model airplanes we used to make? If you held the propeller, the whole plane would spin. Same thing.

rScotty

 

[kthompson]

You are probably right on the 20 years. I bought it used and have had it for at least 17 years. Bought it to mow our yard mainly. Have used it to do a lot of mowing with finishing and rough cut mower. It is very nibble and amazing how much it can pull.

 

[K5lwq]

I only use 4WD when I need it because it tears up the ground more. 90% of the time I have no issues with it disengaged. But then again most of the farm tractors I grew up on were 2WD. The 4WDs were center pivot not front end assist.