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Unread 07-12-2010, 01:47 AM   #1
karateka
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1987 YJ Wrangler 
 
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3 Wheel drive?

I was installing a Posi-Lok actuator in my YJ today and I noticed something:

With the differential in 4 wheel drive and the front right wheel off the ground, when the actuator was engaged, the wheel in the air was locked, with the actuator disengaged, it free-spun.

It made me think, with one wheel off the ground, will the front left lose traction? Does the front axle have a limited slip differential? If I have the transfer case in 4x4, but the actuator is not engaged, does that mean I will have traction on the left front but not the right front?

It seems to me that without the 4x4 actuator engaged, when placed into 4x4, the vehicle would be 3 wheel drive. Is this correct?

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Unread 07-12-2010, 03:22 AM   #2
Mark05059
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you have experienced how an unlocked differential works. If you had 1 wheel in the air on both front and rear then you would find you actually have "2 wheel drive"
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Unread 07-12-2010, 03:28 AM   #3
karateka
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Quote:
Originally Posted by Mark05059 View Post
you have experienced how an unlocked differential works. If you had 1 wheel in the air on both front and rear then you would find you actually have "2 wheel drive"
I'm fairly familiar.... I have been off roading in my 92 Chevy K1500 for 15 years. It too has a differential in the front and the dreaded spinning wheel in the air problem.

When I took the actuator cover off the axle and saw how the mechanism works, I was hoping the jeep had a solid axle design and the mechanism simply engaged the right front wheel. Obviously not...

If and when I need to replace the front differential, I might just throw in a spool and use the actuator to disengage the front right wheel when I need to turn.
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Unread 07-12-2010, 03:50 AM   #4
sahara_tj
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If you put a spool in, there will be no "disengaging" of one wheel at a time, because the spool mechanically locks the two axleshafts together in the center of the differential. If you're doing this in a front axle application, make sure you have manual locking hubs, because a spool in the front end will make it impossible to turn on the road unless the axles can be manually unlocked.
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Unread 07-12-2010, 04:07 AM   #5
karateka
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Quote:
Originally Posted by sahara_tj View Post
If you put a spool in, there will be no "disengaging" of one wheel at a time, because the spool mechanically locks the two axleshafts together in the center of the differential. If you're doing this in a front axle application, make sure you have manual locking hubs, because a spool in the front end will make it impossible to turn on the road unless the axles can be manually unlocked.
Ahhh yes.... the jeep hubs are always connected to the shaft... hmmmm... I guess that's why lockers are so popular..
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Unread 07-12-2010, 07:18 AM   #6
muddy93
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^^^what was said above is true with a TJ, however, sense you have a YJ, it's not compleatly true.
With a spool in the front of a YJ, (assuming you keep the axle disconnect) you CAN disconnect the passanger front tire. But you will most likely get vibrations from your front drive shaft at highway speeds, as it will always be spinning, even in 2wd.
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Unread 07-12-2010, 09:41 PM   #7
sahara_tj
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with a spool though, the two tires will still be connected inside the differential by the axleshafts. even if you disconnect the front right, as you say, both wheels will get the same amount of power because of that link (the spool). also, i'm no expert on the vacuum disconnect thing in YJ's, but in most vehicles that don't have manual locking hubs, the internals in the front end and the front driveshaft will always be spinning, even in 2wd. there is no torque applied to the driveshaft via the transfer case, but the shaft will still spin. this is because the outer stub axles are always connected to the wheels via the hubs.
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Unread 07-12-2010, 11:20 PM   #8
imstillatwork
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I think there is some confusion in here. Muddy got it right

A YJ (specifically) has a front axle disconnect (the vacuum disconnect on the passenger side of the front axle)

If you spool the front differential, and are in 2wd, the driver side front wheel will turn the front driveshaft and will be neutral at the xfer case. The passanger side wheel spins freely because the axle vacuum disconnect is OPEN (passenger side axle is NOT connected to the front diff at this point)

If you spool the front and are in 4wd (front axle disconnect is now engaged) the front axle will be solid. both wheels are mechanically connected and solid.

So saraha tj, a YJ front spool can behave almost like a open diff if the vacuum disconnect is open. The vacuum disconnect happens automatically as you select 2wd / 4wd, although you can re-wire it to a switch if you really wanted to.
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Unread 07-12-2010, 11:47 PM   #9
sahara_tj
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Quote:
Originally Posted by imstillatwork View Post
I think there is some confusion in here. Muddy got it right

A YJ (specifically) has a front axle disconnect (the vacuum disconnect on the passenger side of the front axle)

If you spool the front differential, and are in 2wd, the driver side front wheel will turn the front driveshaft and will be neutral at the xfer case. The passanger side wheel spins freely because the axle vacuum disconnect is OPEN (passenger side axle is NOT connected to the front diff at this point)

If you spool the front and are in 4wd (front axle disconnect is now engaged) the front axle will be solid. both wheels are mechanically connected and solid.

So saraha tj, a YJ front spool can behave almost like a open diff if the vacuum disconnect is open. The vacuum disconnect happens automatically as you select 2wd / 4wd, although you can re-wire it to a switch if you really wanted to.
So the vacuum disconnect disconnects the passenger side wheel from the axleshaft at the hub? I guess I'm just not understanding this whole vacuum disconnect thing.
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Unread 07-13-2010, 02:33 AM   #10
T-WOLF2010
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well its a two piece axle shaft on the passenger side so when the vacuum disconnect or the posi-lock is disconnected the passenger side axle is two separate pieces


the on on top is a two piece yj shaft the bottom is a one piece like xj's and tj's
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Unread 07-13-2010, 03:44 AM   #11
karateka
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Quote:
Originally Posted by imstillatwork View Post
I think there is some confusion in here. Muddy got it right

A YJ (specifically) has a front axle disconnect (the vacuum disconnect on the passenger side of the front axle)

If you spool the front differential, and are in 2wd, the driver side front wheel will turn the front driveshaft and will be neutral at the xfer case. The passanger side wheel spins freely because the axle vacuum disconnect is OPEN (passenger side axle is NOT connected to the front diff at this point)

If you spool the front and are in 4wd (front axle disconnect is now engaged) the front axle will be solid. both wheels are mechanically connected and solid.

So saraha tj, a YJ front spool can behave almost like a open diff if the vacuum disconnect is open. The vacuum disconnect happens automatically as you select 2wd / 4wd, although you can re-wire it to a switch if you really wanted to.
Ok, then I WAS right... I could spool the front differential and run in 2wd as long as the posi-lok was disconnected. If I engaged the transfer case and NOT the posi-lok, then I would have 3 wheel drive, and I could turn... when climbing hills head on, I could engage the posi-lok and have 4 wheel drive and it would behave as if I had a front locker with no rear locker.

I've done my own spool by simply welding the pinion gears. If I ever lose my front differential, I might do that because I plan on eventually swapping out the rear for better gears anyway.
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Unread 07-13-2010, 07:04 AM   #12
jbeebe
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if i were you i would just spend a couple hundred bucks for an aussie locker in the front. done.

the aussie replaces only your spider gears, and is (in my opinion and many others) the best automatic locker on the market.
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Unread 07-13-2010, 10:16 AM   #13
imstillatwork
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Like someone said earlier though, you will be spinning the front drive shaft 100% of the time, always and that can cause a lot of vibrations nearing highway speeds.
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Unread 07-13-2010, 10:45 AM   #14
jbeebe
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Quote:
Originally Posted by imstillatwork View Post
Like someone said earlier though, you will be spinning the front drive shaft 100% of the time, always and that can cause a lot of vibrations nearing highway speeds.
only if your ds is bent. when i got my aussie i got vibes bc it was bent, so i got a used one that was nice and straight and it's perfect.
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