Actual Drive Wheels in 88 Cherokee?

[Rick Anderson]

In a FWD car, where the torque reaction from the motor will not lift one wheel and change traction between the two wheels, with an Open differential, I have laid a pair of tire tracks for a good 10 ft. Eventually the tire traction will differ and the open diff, only one tire continues to spin and one of the tracks will typically be a few feet longer than the other.

Remember, with most RWD, the torque reaction with the drivetrain will tend to lift one wheel slightly and vary traction, thus you almost always get a sole tire track during a burn out.

Correct me if I'm wrong on these rudimentary observations and understanding.

An open differential
*Allows the wheels on the axle to spin at different speeds, with no resistance (other than a small amount of friction).
*It CAN transfer power to BOTH wheels or only ONE wheel.
*It does NOT bias the power that goes to any wheel.
*If the wheels are spinning at the same speed, with the same traction, (the differential part is not working, i.e. the spider gears are not turning at all) both wheels will get equal power. Both paths of resistance are equal, thus there is no bias toward either path.
*If the wheels are spinning at different speeds or have different traction, (the differential part is working, i.e. the spider gears are turning) the power will bias toward the "path of least resistance".

A limited slip differential (clutch or cone type)
*Allows the wheels on the axle to spin at different speeds, but with resistance from the clutch/cones.
*It WILL transfer power to BOTH wheels, NEVER only ONE wheel.
*It does NOT bias the power that goes to any wheel, but the clutches/cones prevent all power going to only ONE wheel.
*If the wheels are spinning at the same speed, with the same traction, (the differential part is not working, i.e. the spider gears or clutches/cones are not turning at all) both wheels will get equal power.
*If the wheels are spinning at different speeds or have different traction, (the differential part is working, i.e. the spider gears and clutches/cones are turning) the power will take the "path of least resistance" BUT, the resistance of the Clutch/Cones will limit the amount of difference in speed of the wheels and thus force power to thru the other path as well. It clutches doesn't really bias the power toward the higher traction/slower spinning wheel, it just keeps the lower traction/faster spinning wheel wheel from taking up all the power.

A locker:
*Does NOT allow the wheels on the axle to spin at different speeds.
*It WILL transfer power to BOTH wheels.
*It does NOT bias the power that goes to any wheel, both wheel will receive equal power, because there is no alternative path for it to go.
*The wheels can ONLY spin at the SAME SPEED, if turns or traction require the wheels to spin at different speeds the tires have to slip (break traction) or break the drivetrain.
*Since there is NO difference in wheel speed, then the effect is reversed, the drive train is forced to create a difference in traction to keep the power even, thus the tire required to spin faster will break traction.

A Torsen LSD:
*Allows the wheels on the axle to spin at different speeds, with little resistance (perhaps additional friction from more and bigger gears involved).
*It WILL transfer power to BOTH wheels, and rare cases ONE wheel (although most also have clutches to prevent only one wheel getting power).
*It does BIAS the power that goes to the wheels toward the higher traction wheel, the gears are preloaded to reverse the path of the power. In rare cases, like one wheel with absolutely zero traction (like the wheel lifts in the air) the toque BIAS will not work. There are clutches included in a lot Torsen LSD to cover this scenario and still keep both wheels turning.
*If the wheels are spinning at the same speed, with the same traction, (the differential part is not working, i.e. the bias gears are not turning at all) both wheels will get equal power.
*If the wheels are spinning at different speeds or have different traction, (the differential part is working, i.e. the bias gears are turning and the pre-load of the gears forces the power in the opposite direction) the power will take the "path of greater resistance" and most of the power will go to the higher traction/slower spinning wheel.

There are even more types of differentials, using things like fluid coupling, etc.

Just when you head is starting to hurt, you have remember, that there has to be a differential between both front and rear axles as well. (Someone correct me if I'm wrong on the following).

AWD - Open type differential, that allows front/rear axles to spin at different speeds with no bias.
Full Time 4WD - Limited Slip type differential, that allows front/rear axles to spin at different speeds but limits the amount of difference, so NOT all the power can go toward one axle.
Part Time 4WD - Locker type differential, that forces both front/rear axles to spin at the same speed.

I think there are some AWD/Full Time 4WD setup with the sophisticated LSD's that bias power toward one axle over the other, etc.

 

[mcnamaag]

So in my 87 Wagoneer my 4x4 selector reads 2 WD, 4 Lock,4 WD, N, 4 LO. Tell me how this works.

 

[Rick Anderson]

http://auto.howstuffworks.com/four-wheel-drive.htm

Now I'm in over my head, someone is going to have to correct me somewhere here, because I know I'm going to get some of this wrong. I don't know the particulars of a '87 Wagoneer, so I'm going to be generic.

2WD - A clutch is disengaged on the front hub, that the chain is wrapped around and going to the front driveshaft, thus the driveshaft is allowed to spin freely. Your just driving the rear wheels directly.

4Lock - The differential (inside the hub that the chain wraps around on the rear axle shaft) is locked up, so the front/rear driveshafts spin at the same speed, making it a Part-Time 4WD. If you have locker differentials in the axles, they may also be locked up as well. If its just a "Part-Time" 4WD transfer case, then moving to 4Lock may just Lock-Up the axle differentials. Your driver manual will tell you exactly what of the above scenarios is happening in your case.

4WD - The Differential (inside the hub that the chain wraps around on the rear axle shaft) is unlocked, so the front/rear driveshafts can spin at the different speeds, making it a Full-Time 4WD or AWD. But torque will naturally bias toward the path of least resistance and go toward the axle with less traction/spinning faster and let one axle spin while the other is stays still. (Unless the differential is also a LSD). If its a "Part-Time" only transfer case, this position may only unlock the front/rear axle differentials while your still in "Part-Time" 4WD, with front/rear axles locked at the same speed. Again, check your driver's manual to figure out which scenario is yours.

N - Unlock the differential between the front/rear driveshafts and disengage the clutch for the front driveshaft and both input shaft will spin idlely, not transferring any power. As well, the planetary gear, unlock both the planet gears and the ring, and the input shaft would spin idlely as well, most likely how its done on Part-Time 4WD only transfer case.

4LO - Same as 4 Lock, but the planetary gears are engaged (by a band or clutch) to spin the output at a different ratio, thus an additional lower gear being outputted to the wheels.

To drive around on the street, i.e. 4 wheels have good traction, you have to have a differential between the drive wheels. So;

*2WD, just 1 between the 2 rear wheels. An LSD here will make sure that one of the two will not spin taking all the power.
*4WD, you need 3 differentials, 1 between both wheels of both the front and rear axles and a third between the front and rear axles. Again, you need LSD's to prevent one wheel spinning and taking all the power. All 3 differentials are open, one wheel spinning will take all the power. If the axles are LSD, but transfer case an open diff, then if both wheels spun one axle, all power would go to just that axle, and none to axle with traction.

Most transfers cases are Part-Time 4WD, because it expensive to put a differential in there. So the front and rear driveshaft are locked to spin at the same speed. Thats fine off-road or in snow or mud, because the wheels will have to spin at different speeds and that will cause the axles to have to spin at different speeds, if the front/rear driveshafts are locked at the same speed, one or two of the wheels will have to slip a little in turns, on dirt/snow/mud the traction is poor enough that the tires will do this easily. On dry pavement, the tires have to much traction and will backfeed force into the drivetrain and eventually wear out or break something.

 

[Johnny O.]

That cant be right. I know when I wheel that if one tire looses traction the other spins. If what you are saying is correct, then when my fronmt left lost traction my right front would not apply power. Same for the rear. No a locker does just that it locks the 2 axle shafts together so if one wheel is off of the ground and one is on the ground they will both spin at the same speed. If you floor it and the one tire starts smoking it has power to it and the other doesn't. Hince the term "One Wheel Wonder"

Dang ya’ll got worked up quick! Stop and think about what you said….if one looses traction the OTHER one spins? No the tire without traction is the one that’s spinning. So just like old man said….both wheels are no longer able to get power to the ground.
1 wheel with traction & no power + 1 wheel with power but no traction = 0 power on the GROUND.
the wheel is getting power just not putting it down. What old man said is 100% correct. the wheel with the least traction on your one wheel wonder is the one doing the spinning, it has some traction or the car wouldn’t move or smoke the tire so some power is getting to the ground. But we are talking about tires up in the air or in very slick mud…NO traction so NO power to move forward. You got the part about the wheels spinning the same speed with a locker correct and I think if you go back and read what old man said carefully you will find that you said pretty much the same thing in your post. You just said it a different way. :lecture:

 

[nick88xj]

you might want to get rid of the frount vac. with a cable one from rustysoffroad.com iv done mine and its werth it :cheers:

 

[1985xjlaredo]

Dang ya’ll got worked up quick! Stop and think about what you said….if one looses traction the OTHER one spins? No the tire without traction is the one that’s spinning. So just like old man said….both wheels are no longer able to get power to the ground.
1 wheel with traction & no power + 1 wheel with power but no traction = 0 power on the GROUND.
the wheel is getting power just not putting it down. What old man said is 100% correct. the wheel with the least traction on your one wheel wonder is the one doing the spinning, it has some traction or the car wouldn’t move or smoke the tire so some power is getting to the ground. But we are talking about tires up in the air or in very slick mud…NO traction so NO power to move forward. You got the part about the wheels spinning the same speed with a locker correct and I think if you go back and read what old man said carefully you will find that you said pretty much the same thing in your post. You just said it a different way. :lecture:

I stand corrected and I meant to say still spinning.
But how you explained it makes sence

 

[xjpheonix]

stop arging listen to that guy blaine b he is right all day so leave it alone and listen to the man
nice work blaine

 

[xjpheonix]

hey go put one of your feet on a patch of ice and try to run... haha
one legger