4x4 Question

[Neil L]

NH TC29 with Super Steer is in 4 wheel and a sensitive system all the time. You can select fixed 4 wheel when needed.

 

[Keith_B]

Most people on here own CUTs, and any discussion of the 4wd systems will by necessity take that into consideration. The primary reason CUTs come with MFWD as a standard feature is that the MFWD helps to compensate for a lack of weight, in comparison to utility sized tractors.

The line of thinking of not engaging the 4wd until it is needed is faulty. The MFWD is to aid in maintaining traction, and make the CUT safer to operate. An operator negates this safety margin by not taking advantage of the MFWD.

Without the MFWD the CUT can slide more easily on a hill and put you in a turnover situation that could easily be avoided by having the MFWD engaged. A little over a week ago we were cutting a drainage ditch with a potato plow (aka middle buster) that ran down a hillside. We used my BIL's 50 hp David Brown and when he applied the brakes going down hill the tractor would slide 15 or 20 feet, sometimes trying to turn sideways, which put the tractor in an obvious possible overturn situation. We used my Mahindra with the MFWD engaged and did not have that problem. Without the MFWD engaged my tractor would have slid around even more, due to its lighter weight. It would have been ill-advised to have waited until we were sliding down a hillside to engage the MFWD. You engage the MFWD BEFORE you get into trouble, not after.

Obviously, just like the 4wd on a pickup, you do not operate the MFWD on dry pavement, as pavement doesn't allow the wheel slippage necessary for tight turns. My owner's manual specifically says to not operate the MFWD on pavement, or at high speeds as it causes premature component wear.

 

[SPYDERLK]

Most people on here own CUTs, and any discussion of the 4wd systems will by necessity take that into consideration. The primary reason CUTs come with MFWD as a standard feature is that the MFWD helps to compensate for a lack of weight, in comparison to utility sized tractors.

The line of thinking of not engaging the 4wd until it is needed is faulty. The MFWD is to aid in maintaining traction, and make the CUT safer to operate. An operator negates this safety margin by not taking advantage of the MFWD.

Without the MFWD the CUT can slide more easily on a hill and put you in a turnover situation that could easily be avoided by having the MFWD engaged. A little over a week ago we were cutting a drainage ditch with a potato plow (aka middle buster) that ran down a hillside. We used my BIL's 50 hp David Brown and when he applied the brakes going down hill the tractor would slide 15 or 20 feet, sometimes trying to turn sideways, which put the tractor in an obvious possible overturn situation. We used my Mahindra with the MFWD engaged and did not have that problem. Without the MFWD engaged my tractor would have slid around even more, due to its lighter weight. It would have been ill-advised to have waited until we were sliding down a hillside to engage the MFWD. You engage the MFWD BEFORE you get into trouble, not after.

Obviously, just like the 4wd on a pickup, you do not operate the MFWD on dry pavement, as pavement doesn't allow the wheel slippage necessary for tight turns. My owner's manual specifically says to not operate the MFWD on pavement, or at high speeds as it causes premature component wear.

I think the idea is to anticipate the need. It would be nice to have one like this;
Quote: NH TC29 with Super Steer is in 4 wheel and a sensitive system all the time. You can select fixed 4 wheel when needed.

But I think those of us who havnt opted to pay for a sophisticated and near fool proof system are taking responsibility for our choice. For some it is to use the 4WD all the time with its inherent drawbacks of increased; 1) tire and fuel consumption, 2)turning radius with greater surface disturbance, 3)driveline stress, 4) engine and transmission wear, 5) brake wear if used in an attempt to decrease turning radius, 6) etc? - - in return for knowing its on when you need it. For some, in order to avoid these drawbacks, it is trusting yourself and your judgement to recognize the need, and hoping your judgement will be consistent and good. This risk situation, combined with a little luck, turns into the basis for valuable experience in handling a tractor in varying conditions. Possibly, a 4WD NOT ON light would help. It could blink when it detected front vs rear slip?
Larry

 

[whitetiger]

The 4X4 in a 1999 and new GM pickup and SUV's have an optional system (may be standard now) computer controled mode called Auto-something. I can not remember how it is labled right know, mine is a 2500HD which did not offer it.

Timber, your description of your truck system is a modern version of the full-time drive system of the 70s. It has no connection to your vehicle computer other than to trigger lights in the dash and engage the front axle disconnect if so equipped.

When in 2 wheel high, that's all the drive you have.

When it's in 4 wheel auto it is functioning as the previous mentioned full-time drive system splitting power to each axle. Similar to your semi rear ends when the power divider is unlocked. To prove this, jack up either end of your truck until both front or rear wheels are off the ground. Engage 4 wheel auto and try to drive off the jack. It will just spin whichever axle you have jacked up and won't move the vehicle.

When it's in 4 wheel high it is locked in 4 wheel drive and demands equal rotation of the front and rear driveshaft. Similar to your semi rear ends when the power divider is locked. If you jack the truck as described above, it will drive off the jack. This is what your B7800 has when you engage MFWD with the lever.

When it's in 4 wheel low it's locked in 4 wheel drive but is operating in low range of the T-case.

 

[RedRocker]

I hope I live long enough to wear out my tractor. I plan on wearing out all of the drive train at the same time, I don't see much need in having a pristine front drive axle on a worn out tractor. If I'm in the dirt mine is in 4WD.

 

[N80]

For some it is to use the 4WD all the time with its inherent drawbacks of increased; 1) tire and fuel consumption, 2)turning radius with greater surface disturbance, 3)driveline stress, 4) engine and transmission wear, 5) brake wear if used in an attempt to decrease turning radius,

The problem is that the things you have listed are 1) not true for every model of CUT 2) not necessarily true for any CUT and 3) in the cases where they are true they are often trivial to the point of being meaningless.

Tire and fuel consumption: At least one manufacturer says their tractor runs more efficiently in 4wd. Also, if driving on anything but hard dry surfaces, tire wear due to 4wd is going to be meaningless.

Turning radius and surface disturbance. Having the front engaged on my tractor has no effect on turning radius. The outside tire does disturb the ground surface as you mention. When that is a concern, I take it out of 4wd. but that's to svae the grass, not the tractor.

Driveline stress. Opinions vary wildly here and very probably the effect varies between brands and models. But for those who constantly switch in and out of 4wd, if you are switching in only when you start to lose traction, you are probably putting as much or more unneccessary stress on the driveline as the always 'in' crowd.

Engine and Transmission wear. Again, very probably trivial at the most and again, erring on the side of putting it in 4wd too late or too infrequently is likely to be just as costly if not more.

Brake wear. I can see how that might be an issue. For those using one wheel braking it might be a legitimate concern while in 4wd. I don't know.

My point here is that some make the decision sound like its a black and white thing. Maybe you didn't intend it that way but it sounds like you're saying 'leave it in and tear it up'. I just don't think it is quite so simple or so cut and dried.

And in the long run, if each of us follows the owners manual and uses a little common sense, either aproach is likely to be fine and our tractors are likely to out survive their owners, front drive line and all.

 

[Timber]

I leave mine in 4 wheel drive all the time. I don't cut grass with it and I am never on pavement except to put it in the garage. Mine is a little difficult about going in & out of 4 wheel drive anyway. I bought my tractor to dig and to use as an all train fork lift.

 

[whodat90]

Lemme throw my hat into the ring with some facts. First will address some of the later posts; the traction sensing transfer cases in some trucks. GM has autotrack. In this the transfer case has an electronically controlled clutch pack that uses the abs sensors to note a difference in wheelspeed between front and rear wheels and couples the front driveline as needed to equalize the wheelspeeds. It works well, I have it in my yukon. Next (although before chronologically) is the jeep quadradrive system. First iteration used a viscous coupling that drove both front and rear driveshafts. Worked well, but was capable of sending all the power to one driveshaft with the least traction. Next was a different quadradrive, where the power went straight to the rear driveshaft, and the rear front driveshaft was coupled to the rear by the viscous coupling. This created a primarily rear wheel drive vehicle that started adding torque to the front driveshaft as the two driveshafts started spinning at different speeds. Next is the new quadradrive, which uses an oil pump to lock a clutch pack that couples the driveshafts together. If there is any speed difference between the driveshafts the pump pumps and applies pressure to the clutch pack coupling them together.

Next, the comparison between a truck's 4wd system and your tractor's: Unless you have a mower deck and loader on your truck, the comparison is irrelevent. Different applications and different environments.

Next, the pointing out that front drive systems are more complex than rear drive systems: duh. A rock is much less complex than your engine, so should you stop using your engine? If it does in fact add wear that would otherwise not be there, so what? When in 80 years you finally wear out your kubota, do you want to wear it out except the front axle? Have you any actual proof that under normal use of the front drive system the front axle wears out more quickly than any other part of the tractor? If not, then what's the problem? If the tractor lasts 5000 hours and the front axle lasts 5000 hours, then so be it. A properly designed system, regardless of complexity, will last the life of the tractor. Using 4wd on pavement with a full load in the loader will cause damage, but that's operator error rather than normal operation.

Finally, use it if you want to. I've got a little B7200D 4wd with turf tires. Sometimes I need 4wd. Sometimes I don't. I use it when going over rough terrain, not only for the drive traction but for the additional braking available through the drivetrain. I use it when tilling just so that it doesn't throw the tractor around when I hit rocks. I sometimes use it when bushhogging just because it helps offset the inertia of the mower (mower swings side to side and wants to pull the front of the tractor around a bit over bumps and when turning) I use it when using almost any ground engaging implement, largely because I don't typically use the ground engaging implements on pavement. I use 2wd almost all the rest of the time. If it's needed, use it. If it isn't, but it isn't hurting anything, use it. If it's not needed and it's use is either contraindicated or not recommended, don't use it. But most of all, don't be afraid that using it is going to cause your front axle to wear out or break long before the rest of the tractor. Your owner's manual is your best guide.

Edit: Terminology clarification: Jeep's first modern awd system was quadratrack, the second was quadratrack 2. The latest version is quadradrive.

 

[dirtworksequip]

Geez, that snowball rolled from New York clear to Texas. So, to push it back to New York from Texas should I use my 4 wheel drive? Great post by everyone, but did we learn anything?

 

[daTeacha]

Maybe. I did an inadvertent experiment yesterday that might give you guys something else to chew on.

I was working with the loader/grapple picking up fairly big log ends and stumps to take to a burn pile. I was working the wooded pasture, hilly rough ground, driving over arm thick logs and such. I had a heavy load in the bucket -- nothing really huge, but enough so I knew it was a good load, I 5' x 30" or so, wet half rotted oak log with a huge knot.

I was moving slowly uphill, climbing over a small log, and the tractor stalled ou the HST -- engine bogged down, tractor didn't move, tires didn't spin. Then I noticed I was in 2wd, shifted to 4wd, and moved right out, no hint of stalling the hydro.

Point -- there was obviously more strain on the hydro in 2wd than in 4wd. This would also translate to greater strain on the rear axle than when 4wd is engaged and the work load is divided between 2 axles.

So, does using 2wd to save miniscule amounts of wear on the front drive axle system cause a corresponding amount of additional wear on the rear one that would not occur had the front end been engaged?

Have fun!