Why no 4 wheel drive on roads?

[ning]

Until you get to the full sized tractors, the front axle is usually a locked differential when engaged.

It's a similar issue.

If the front axle is a locked differential when engaged, you still get driveline tension and wheel hop; in this case, the tension will be between the front and rear diffs (because the front axle will still be turning at a different speed than the rear) as well as to the right and left of the front diff (between the front diff and each of the wheels) because once again the left and right front wheels will be turning at different rates.

The same thing happens in the rear when you lock the rear differential and try to turn.

Not sure about trying to compare it to a 4wd truck which would have an open, remote, or automatic differential locking system.

I stated "4wd truck" in particular because 4wd systems are generally considered to have a solid connection between front and back (ie, transfer case) as opposed to a center differential, which may or may not be lockable (generally considered to be "AWD" and specifically called out in my posting).

 

[CausticUrbanCoast]

I do not think this is correct.

Correct me with specifics. I know both my sub compact and compact tractors do not have locked front differentials...

You are right. Now that I think on it, the front axle is a type of bevel pinion drive.

 

[Torvy]

My first experience driving a 4wd vehicle was in 1976. We had an IH Scout. Had to get out and lock the front hubs for 4WD. The instructions back then were to avoid driving in 4WD on dry pavement. I'm no engineer, but I don't think it is just a tractor thing.

 

[Jstpssng]

My Colorado has a knob to run the electric to engage 4WD. I'm constantly hitting it with my knee when getting in or out of the truck. I know within 50 feet that it's engaged, because the truck starts bucking and binding.

 

[k0ua]

I do not think this is correct.

Correct me with specifics. I know both my sub compact and compact tractors do not have locked front differentials...

No, they don't BUT there isn't a center viscous coupling Between the front and rear differential either. So the driveline windup that can occur on solid surfaces can't slip or cannot be relieve by a center coupling differential. Your CUTS are solidly locked Between the front and rear. Sure there is differential action in your front differential as well as your rear differential BUT none between the differentials.

 

[mcfarmall]

Do you have a 4WD pickup or SUV? If so, put it in 4 High and drive it that way for 90 days and report your conclusions back to us.

 

[sandman2234]

I do not think this is correct.

Correct me with specifics. I know both my sub compact and compact tractors do not have locked front differentials...

Neither are mine!
David from jax

 

[Agvg]

It just a bad design of the drive train, tractors with full time 4WD do eksist but might be a little on the expensive side

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Award-winning masterpiece. 500 HP. The new Fendt 1000 Vario. Typically Fendt. You can find all the highlights here.

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This drivetrain drives front and rear totally independent so it can do very cool things and are very effective, steeples s from zero to 60km/h.

 

[RoostersGarage]

I wouldn't say it's a bad design, I'd say it's a less expensive design and since tractors spend most of their life on soft surfaces there's no reason to have the added expense of full time 4wd. Plus, it's very expensive to transfer a lot of torque through a full time 4wd or AWD system and the mechanical lockup tractors have is more efficient.

 

[Agvg]

I have spent a few hours to day in a Toyota Hilux and has very few good things to say about 4WD whitout some form of constant 4WD, it's simple and there stops all advantages.

A 4WD as Fendt makes them will be very effectiv, when you can distribute torque between front and rear and use the front axel to activ help steering will also be very nice.