Differential Action in 4WD

[Ordite]

I have had a JD 3320 with 300CX FEL for about a year. This weekend I was moving some dirt that was dumped in my friend's driveway and dumping it behind a low retaining wall. I have noticed in the past, when moving snow, that the front differential does not seem to function in 4WD in the same manner as 2WD when making a sharp turn. When manuevering around this weekend in 4WD I thought that the rear tires were also scuffing when making a turn. Are the differentials locked when using this tractor in 4WD? If so, doesn't this put a lot of stain on the drive components with a load in the bucket and a counter weight on the rear? Does anyone have any knowledge regarding this situation?

 

[fgross335_2210]

I don't think either diffy locks up in 4WD. But being in 4WD means all 4 tires are trying to turn at the same speed, meaning that potentially 3 of the 4 tires are 'scrubbing' at any point in time......

 

[Duffster]

When turning, the front wheels a traveling a farther distance(making more revolutions) then the back. You won't notice this in 2 wheel but in 4 wheel the front axle is locked with the front amd the extra revolution has to be made up somewhere.

 

[Ordite]

Thanks for the responses. These explanations make sense and are something that I hadn't thought about. I didn't see how the differentials could be locked without some eventual damage to the drivetrain.

 

[orlo]

Right. It' no different than a 4wd truck if you turn sharp. Either one of the front or one of the rear wheels will slip.

Deere actually gears the front axle faster than the rear (slightly) on at least some of the MFWD tractors (States this in the manuals). Maybe they 'average' out what the speed should be between perfectly straight and a full turn. Same reason not to use 4wd on hard surfaces as on a truck.

Also the reason the front wheels (Usually the front) dig up the lawn a lot more when turning in 4wd.

 

[Redneck in training]

Most four-wheel cars have three differentials. Central differential is connected to the engine and divides power between front and rear. Tractors don't have central diff. Front wheels on most tractors turn somewhat faster then rear. I don't know exactly why but probably to lessen front wheel slippage when turning as mentioned in the reply above.

 

[GreatWhitehunter]

Your 3320 also has a rear wheel diff lock. It's located behind your left foot.

Matt

 

[kebo]

I have had a JD 3320 with 300CX FEL for about a year. This weekend I was moving some dirt that was dumped in my friend's driveway and dumping it behind a low retaining wall. I have noticed in the past, when moving snow, that the front differential does not seem to function in 4WD in the same manner as 2WD when making a sharp turn. When manuevering around this weekend in 4WD I thought that the rear tires were also scuffing when making a turn. Are the differentials locked when using this tractor in 4WD? If so, doesn't this put a lot of stain on the drive components with a load in the bucket and a counter weight on the rear? Does anyone have any knowledge regarding this situation?

Most 4x4's (this includes atv's, trucks, tractors) will be slightly harder to make sharp turns due to all the extra gears in the entire driveline binding up. You can feel this binding being released sometimes, its like the truck or tractor wants to lurch a short distance. This is normal. Heck, when I put my F-150 in 4x4, I can't hardly turn it sharp without really hitting the gas. All that extra friction in the driveline makes it harder for the engine to overcome. Like someone else already mentioned, your rear diff lock must be manually engaged for it to lockup the rear end. I think your tractor (like most) has an open diff in the front axle so it can't really lockup at all.

 

[Duffster]

Most 4x4's (this includes atv's, trucks, tractors) will be slightly harder to make sharp turns due to all the extra gears in the entire driveline binding up. You can feel this binding being released sometimes, its like the truck or tractor wants to lurch a short distance. This is normal. Heck, when I put my F-150 in 4x4, I can't hardly turn it sharp without really hitting the gas. All that extra friction in the driveline makes it harder for the engine to overcome. Like someone else already mentioned, your rear diff lock must be manually engaged for it to lockup the rear end. I think your tractor (like most) has an open diff in the front axle so it can't really lockup at all.

I don't think that is extra gears binding but the tires binding on the pavemant.

 

[vsteel]

The front wheels on a lot of 4X4's turn faster because it helps handling. If they turn at the same speed the vehicle tends to "push" around a corner instead of letting the front wheels take the lead.