Open Differential Confusion...?

[jschenck]

Tried to smoke the back tires on the Libby today after work, but the tires wouldn't break loose. The pavement was soaked from a nice hard rain, and the tires are less than half tread left. The Jeep just hooked immediately and launched forward. Which, I wasn't expecting since the pavement was wet and the tread is low on the tires. Assuming that I have a plain-old Open diff, I was expecting at least the right wheel (which I'm assuming is the drive wheel) to spin, but nothing. I was from 0-40 in fairly short stretch, so I doubt the 3.7 is short on power for some reason. So, I decided to swing down a dirt road on the way to see what was up. At a dead stop, I hammered it, both wheels slinging gravel for as long as I held it in. However, both spin marks were equal length and it appears that both tires were throwing just as much gravel. Again, not was I was expecting from an open diff. I expected the right tire to throw more gravel and spin a longer line than the left tire. Then, I tried a rolling start of about 15MPH and hammered down on the throttle, again, both tires throwing equal amounts of gravel and leaving matched spin marks the whole time I held it in. If my Jeep indeed does have an open differential, it functions a little differently than other ones that I've had experience with. My old '84 F-150 would smoke one tire (the right one) all day, but the left would never leave a single spin mark.

My question is, is that normal open diff function for the 04 Libby Limited with 3.7, or does it have a LSD, or Locker in it?

I have looked over the factory slip and checked the diff cover and found no evidence from either source that it has a factory LSD, so perhaps I'm just not as knowledgeable as I think I am.

Any insight would be greatly appreciated!!

 

[JeepJeepster]

Normally there is a tag on the right side of the axle saying if its open or has an lsd. Sure fire way to tell is to jack it up and try to spin 1 back tire. If the other spins in the opposite direction then its open. If you cant turn the tire then its lsd (given the ebrake is off and the ****** is in P).

Either tire can spin, doesnt have to be the right tire, just fyi.

 

[tjkj2002]

You have the factory trashloc.

 

[Ry' N Jen]

And your jeep is gutless with the 3:73's out back.
With 4:10's and the rear locker engaged I can roast the tires no problem!

 

[jschenck]

You have the factory trashloc.

TJ, I just crawled under the rear end and found the axle tag, " 8.25 KJ, 3.73 open case".

So, how do I explain the seemingly "locked" wheels if the tag says open diff? I will try jacking the rear up and spinning a wheel, but that will be at some unset time in the future.

I don't have all the paperwork from the previous owners, so it's possible that they could have had a trashlock (or other LSD) installed after purchasing the vehicle.

But, making the assumption that it IS IN FACT an open case, how do I explain the wheels leaving identical spin marks in gravel?

 

[Cherrie]

Zombies?

 

[trent.brown]

Do your tires bark going around turns? If so, your differential isn't differentiating through modification or something causing your spider gears to lock. If your tires aren't eating pavement going around everyday turns, then someone has put an lsd in there.

 

[jschenck]

Do your tires bark going around turns? If so, your differential isn't differentiating through modification or something causing your spider gears to lock. If your tires aren't eating pavement going around everyday turns, then someone has put an lsd in there.

Trent, as far as I can tell it handles turns normally. No barking tires and no excessive/uneven tire wear. There never seem to be any strange noises from the rear end either.

 

[hectikart]

ESP/TCS can somewhat simulate an LSD...

 

[trent.brown]

With my aussie, if I put a little power on it on a light turn, I can lock the rear end and the inside tire will chirp. Going around the same turn lightly, the locker will unlock, make some light clicks, but behave like an open diff.

I also think there is an lsd in there, but maybe a gift from previous owners. Spin the wheels and find out. All you need is a chock, a jack, and jackstands. Or you could put it up on cinder blocks like we used to do. On second thought, leave the blocks to us poor folks back in the sticks.

 

[jschenck]

With my aussie, if I put a little power on it on a light turn, I can lock the rear end and the inside tire will chirp. Going around the same turn lightly, the locker will unlock, make some light clicks, but behave like an open diff.

I also think there is an lsd in there, but maybe a gift from previous owners. Spin the wheels and find out. All you need is a chock, a jack, and jackstands. Or you could put it up on cinder blocks like we used to do. On second thought, leave the blocks to us poor folks back in the sticks.

No clicking. I know there isn't a locker back there, there is never an chirping from the rear tires, even wen I push it hard through turns.

ESP/TCS can somewhat simulate an LSD...

I don't think my Libby has either of those. I have no way to disable them, which I know was an option on some Libby's that came with those programs.

 

[tjkj2002]

The original onwer could have had a LSD installed for any amount of reasons and it could be labeled wrong.You don't have ESP or traction control since you have a '04 KJ,those did not get installed till '06+.

 

[jschenck]

Went out this morning and jacked up the rear of the jeep, got ahold on the left rear tire and tried spinning it forward. What do you know, she spun free and easy, and the right rear tire? Spinning in the opposite direction. This means that the Jeep indeed does have an open differential and that I am still confused as to why in three back to back situations it would behave as if it were locked or had a LSD...

Now that an LSD is clearly out of the picture, anyone have any other ideas as to why this open diff was behaving like a locked or LSD rear end?

 

[cplchris]

idk if they make one for the 8.25 but it sounds like it could be a torsen diff? anyone else thinkin the same?

 

[Ry' N Jen]

Get someone to take a video of said gravel burnout with both rear wheels spinning with an open diff. This I have to see to believe.

 

[jschenck]

Get someone to take a video of said gravel burnout with both rear wheels spinning with an open diff. This I have to see to believe.

Ry, per your request, here is a video... Notice the right wheel spins the whole time, the left starts to spin immediately, catches traction for a split second, then breaks loose again, spinning just as much as the right.

Open Diff Wheel Spin - YouTube

 

[Ry' N Jen]

I think it's just the fact that the surface is very loose as our KJ has done the same thing in similar situations.
Take it our on pavement and place your left foot on the brake peddle and load up the torque converter and see if you can get both tires to break traction or at least "Chirp" upon launching.
Other that that I think it's just the loose surface you are launching from.
ie. The passengers side tire looks to be on looser surface that the drivers side tire.

I just tried it with our KJ (Equipped with ARB lockers front and rear) and our KJ does the same thing with one tire in looser surface gravel...

 

[tjkj2002]

Ry, per your request, here is a video... Notice the right wheel spins the whole time, the left starts to spin immediately, catches traction for a split second, then breaks loose again, spinning just as much as the right.

Open Diff Wheel Spin - YouTube

See now you have 2 different stories as you originally quoted..........

both wheels slinging gravel for as long as I held it in. However, both spin marks were equal length and it appears that both tires were throwing just as much gravel.

In a open diff you do not have a "drive wheel".Torque follows the path of least resistance be it the left or right side.If equal resistance is achieved both wheels spin the same.

Also just because the pavement was wet does not mean you should be able to spin your tires.Wet pavement is still a high traction surface.

 

[trent.brown]

seems normal to me, I bet if you powerbrake it, only the right would spin.

 

[tjkj2002]

I bet if you powerbrake it, only the right would spin.

Path of least resistance,not always the right rear.In most cases it actually will be the left rear due to how the weight transfers and the engines torque twists the body placing the most weight on the right rear.