Operation in 4 Wheel Drive?

Soundguy · Dec 25, 2004

I would agree.. unliss the jinma have limited slip diffy's.. '4wd' is more like '2wd' . If one front and one rear are off the ground.. tractor won't move. Lock the rear, and one front can still slip.. 3wd..

Soundguy

Brad_Blazer · Dec 26, 2004

It might be a moot point if you have a locking differential but sometimes it helps to apply a little brake to a spinning rear wheel.

bluechip · Dec 26, 2004

Of course this is not a configuration that is unique to Jinma, KAMA or chinest tractors. Most MFWD tractors are like this.
Brad, good point on the brake, that is how many of today computer controlled 4wd systems work, brake the spinning wheel and the remainint one has to turn...

There are a few tractors like the KIOTI DK65 that have front and rear diff locks so you can really dig in with all 4 wheels at once, but it is not normally necessary.

greg_g · Dec 26, 2004

( I would agree.. unliss the jinma have limited slip diffy's.. '4wd' is more like '2wd' . If one front and one rear are off the ground.. tractor won't move. Lock the rear, and one front can still slip.. 3wd..)

Thanks Chris. When put that way, I can now grasp the concept Chip was trying to describe. But I'm curious why - after several hundred hours in 4WD, on three different tractors, in low traction conditions - I've never once observed only ONE front tire turning/spinning.

So I'm going to jump off from where you said "...unliss the jinma have limited slip diffy's...". If the front drive is in fact "open" as Chip describes, why even worry about using 4WD on hard surfaces? Only one front wheel would be driven, the other would just be along for the ride.

It's been my understanding that it is BECAUSE the front drive IS of limited-slip design, that 4WD should be disengaged before driving on hard surfaces. So what am I missing?

//greg//

dieseln · Dec 26, 2004

Sorry - my misconception on a 4wd 'lock' feature on older jimnas... i'll stop using the 4wd on pavement.

bluechip · Dec 26, 2004

The problem from driving in 4wd on hard surface is not in the front or rear diff, but there is NO differential in the transfer case. one front and one rear wheel WILL recieve the power and will be propelled based on the gear ratio regardless of the real rolling ratio of the tires. That can be impacted by inflation, or even the tolerance of the molding process of the tires themselves. No 4wd on hard surface, something has to be able to give and something will, ON pavement it is likely to be something made out of metal that gives, in dirt it is the dirt.

Soundguy · Dec 26, 2004

( that 4WD should be disengaged before driving on hard surfaces. So what am I missing?
)

I also believe the jinma 4wd should be disengaged for hi traction driving. In fact.. just about every 'gear' type fws I've ever seen says to disengage on hi-traction surfaces. I have however seen some FWA systems, or independent hydro drive systems that are ok for hi traction.

It's my guess that while the front wheels can slip side to side.. there is still a possibility of driveline run up from front to rear.. meaning either scuffed tires.. or stressed yokes and shafts.

I obvously don't have one to look at.. or even a manual.. but that would be my 'guess'. so no solid facts here either.

Soundguy

johnk · Dec 26, 2004

Here's a little link on 4 wheel drive that drives to explain things.............

http://www.4x4abc.com/4WD101/def_turn.html

Harrygoodwrench · Dec 26, 2004

Thank you very much John K!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

This thread was going on and on with with useless arguing about 4WD. This is not your AWD car so DON'T use 4WD on hard non slip surfaces, OKAY GUYS,,,,,,,,,,,,,,lets get on with more important things.

johnk · Dec 26, 2004

Merry Christmas and Happy New Year to you Harry. Hope your son is home soon............

John

greg_g · Dec 26, 2004

( This thread was going on and on with with useless arguing about 4WD. This is not your AWD car so DON'T use 4WD on hard non slip surfaces, OKAY GUYS,,,,,,,,,,,,,,lets get on with more important things. )
Sorry this seems to have bored you so, Harry. Some folks like to know the WHY of things. And on this topic, I still don't. But if you are able to contribute something to that end, I'm sure willing to try and learn from it.

//greg//

johnk · Dec 26, 2004

Just to interject, the link I posted explains the WHY to things. Don't see the problem picking on Harry. I feel tension here with no need for it. Have fun, listen to the opinions and use your own judgement. We aren't all tractor GURU's you know..... Just people seeking SIMPLE info on fixes or mods.

Merry Christmas and Happy New Year to All. Just a poor slob who /forums/images/graemlins/shocked.gif has to work in the morning.........

TruChaos · Dec 26, 2004

While I'm a new tractor user, I've driven a 4WD Jeep for 15 years, on and off road.

Reading the Jinma 284 tractor manual and using the tractor proves it's function to be virtually identical to a manual 4WD vechicle. Here's the operational rules in a nutshell.

1) Unless your wheels are slipping, there's no need to use 4WD. Doing so, can increase wear and tear on some driveline parts but, it's not the end of the world. Using 4WD on dry hard surfaces is never a good thing to do. That jerking feeling in the steering when turning is the two axles pulling against one another. This is when the extra wear and tear occurs.

2) If you are in 4WD and are stuck, you can use the axle lock lever to lock the rear axles together. This effectively eliminates the rear diferential and mimics a single axle shaft between the rear tires. Power will be distributed evenly to both wheels in this mode. Driving in a straight line is critical. Why the factory manual say to do this at full throttle, I haven't a clue.

Since, non posi-traction type axles give power to the axle with the least traction, the axle lock lever is a great asset if used properly. Once you're out of the slippery spot DON'T continue to use the axle lock. Turning the tractor with the lock engaged will eventually break the differential axle assembly. The lock lever is the small lever near your right foot while seated on the tractor.

With the Jinma 284 tractor, since the front axle is open and the rear can be locked, the best you will ever have is three pulling wheels at once. The two locked rear wheels and the front wheel with the least grip.

I haven't read the entire thread so forgive me if this is a repeat of anything already stated.

greg_g · Dec 27, 2004

( Just to interject, the link I posted explains the WHY to things...I feel tension here with no need for it. )

John, I've been driving/operating/fixing part-time 4wd vehicles since Moby Dick was a guppy. Not major overhauls, mind you. I do however understand the dynamic principles - and definitely the differences between full-time and part-time 4WD, even between 4WD and AWD for that matter. But the skill level addressed by that article didn't render anything close to explaining the WHY of an "open" front differential on Mike1's JM304 - or by extension, on my tractors either.

Despite the GURU shot, any tension you may sense surely isn't between the folks that are actually exchanging pertinent information here. Once the basic point of the thread - don't use 4WD on hard surfaces - had been reasonably hammered home, I bantered about a few front differential WHYs in the hope of understanding observations I've made concerning my own equipment on my own land. So if you feel that's not simple enough for this forum, I have no problem continuing this discussion with Chip and Chris - privately.

//greg//

ToolManRick · Dec 27, 2004

Too much info here for me to digest and the tension is overwhelming. /forums/images/graemlins/grin.gif Somebody must not have gotten what they wanted for Christmas. /forums/images/graemlins/frown.gif Just kiddin' all.

Okay, my 2 cents worth. AWD systems contain a viscous coupling in the driveline connecting the front and rear drives. When you corner or don't have an exact ratio between the front and rear systems it allows slippage to reduce tire wear, sheared axles or other damage. Jinmas don't have that and that's why it's really tough on the driveline on hard surfaces. Santa was good to me, I got a tilt gage for Christmas!

Soundguy · Dec 27, 2004

It's interesting to look at some of the automotive differences when it comes to 4wd. For instance.. On my mothers ford explorer, it has a limited slip rear end, and a dash switch for 'traction control' which as far as I can tell is some kind of quick brake pulsing for when one wheel slips more than the other.. or drastically more I guess.... hard to say though, as the manual is devoid of usefull info.

Soundguy

shvl73 · Dec 27, 2004

My '01 Explorer has some kind of full time 4wd. The switch has a "auto" mode that I'm told is a 30/70 split front/rear, I'm assuming with some kind of viscous coupling, then 4wd hi & low. There is no 2wd selection. maybe that accounts for the "great" fuel mileage. /forums/images/graemlins/frown.gif
I've never had a manual for it, I'm not real sure how it works.

TruChaos · Dec 27, 2004

The reason a Jinma shouldn't be driven on hard surfaces is just as you stated.

Both front and rear axles are open (not limited slip). Even though they're open axles, one front axle and one rear axle are aways directly connected. When you turn the front wheels, the front and rear wheels turn at different rates. Since they are mechancally connected and are being forced to turn at different rates, one wheel must slip or drag on the ground. This occurs even though you don't see it, since it's small amounts of correction, inches at a time. In snow or mud, this happens easily, on asphalt it creates tremendous loads on some drivetrain components. The only other option is for something to break in the drivetrain. When the rear axle lock is engaged, it gets much worse since three axles are now locked together.

When turning the wheels and driving in an arc (turning) on a tractor or a car, the front wheels travel a longer distance than the rear wheels.

As has been stated, the only way to allow 4WD to be engaged on a hard surface without wear, tear and undue stress on the drivetrain is to add a third differential between the front and rear axles, effectively allowing them to turn at different rates. This is how AWD vehicles work.

Hopefully, this posting won't cause unnecessary reader or drivetrain stress.

cmperry · Dec 27, 2004

I'm glad this subject went into more detail..a little hard to visualize all that goes on inside the drivetrain unless you've torn it all apart and understand it..for people who understand this I can see where this may be "boring".. but for people like me that may be a little slower this was a great thread

thegreatrandini · Dec 27, 2004

I liked it. I now know y I should not drive in 4wd on dry roads in my dodge. Before I just knew not to.... I guess I could have figured it out but I never really thought about Y?