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Discussion Starter · #1 ·
I was out wheelin' over the weekend with some friends in Lapine, Oregon. Wasy trying to crawl through this small crevasse (below). I came to a stop because I could feel one of my rear wheels spinning. I gave it a little bit of gas and heard a loud snap, from what sounded like the passenger side.

After hearing the snap, I got out and checked the CV shafts. Didn't see anything. Got back in, gave it a little more gas and powered out and on to some flat ground. Crawled underneath to check the front pumpkin and give the shafts a closer look. Still didn't see anything. Used 4 wheel drive (lo and hi) a little more that day, seemingly without any problems.

Does anyone know a fool proof way of checking the diff? I thought I could get it up on four jack stands (maybe have to take the wheels off) put it into 4-hi and check to see if any of the CV shafts are spinning off center. Any suggestions or alternate tricks?
 

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Hmm. I believe people heard loud noises when turning. Do you hear anything?
 

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OregonX said:
Does anyone know a fool proof way of checking the diff?

Jack the front wheels, put in 2wd, spin one wheel. See what the other one does, check for noises, cvs etc.
 

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OregonX said:
Offroad said:
OregonX said:
Does anyone know a fool proof way of checking the diff?

Jack the front wheels, put in 2wd, spin one wheel. See what the other one does, check for noises, cvs etc.
Should I be watching the other wheel for even rotation in the opposite direction?
Yep.

When I blew my diff it took about 5-8 rotations of the drivers side wheel before the pass side even moved and then it rotated in the same direction (it should rotate in the oposite diection).
 

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Also check to see if there is any unusual play in the cv shafts. The second time I blew mine the cv shaft on the drivers side was moving back and forth like 2 to 3 inches.

Irish
 

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I had a few of them loud snap noises with no problems until the last snap then I lost 4 wheel drive. I grabbed the front axle and it was so loose I could pull it out with two fingers. Turns out the axle was broken inside the rear but that didn't cause the problem it was the teeth on the ring gear snapping off. Well one or two teeth breaking off the ring gear may not be noticable but when one off them teeth get stuck in the pinion well thats all folks. When they opened my front diff up there wasen't any teeth left on anything and the ring carrier was cracked in half. So I would say take it to the dealer and tell them to fix it.
 

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Discussion Starter · #10 ·
geo9974 said:
So I would say take it to the dealer and tell them to fix it.
I'm going to put it up on jackstands on Saturday just to spin the tires and find out what happens.

As far as just taking it to the dealer... I might have to use the jedi mind trick to fool them into thinking my 285/75/16s are actually 31s or 32s. I have a pretty good guess what their answer is going to be.

But let's hope it doesn't come to that.
 

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As far as just taking it to the dealer... I might have to use the jedi mind trick to fool them into thinking my 285/75/16s are actually 31s or 32s. I have a pretty good guess what their answer is going to be.

This is where putting the stock wheels and tires back on your truck comes in handy (if you could afford to buy new rims for your 285s) :geek:
 

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dnorton said:
As far as just taking it to the dealer... I might have to use the jedi mind trick to fool them into thinking my 285/75/16s are actually 31s or 32s. I have a pretty good guess what their answer is going to be.

This is where putting the stock wheels and tires back on your truck comes in handy (if you could afford to buy new rims for your 285s) :geek:
Sheeesh! There are a lot of people here that live near you, have someone with stock size trade you out for the fix, they won't mind sporting a set of 285's for a week or two. Then you are covered. I'd let you use my spare stock set in a heartbeat. Come on someone! Offer up!

We can all stand together ....or fall one by one.

MC
 

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Discussion Starter · #13 ·
Offroad said:
OregonX said:
Does anyone know a fool proof way of checking the diff?

Jack the front wheels, put in 2wd, spin one wheel. See what the other one does, check for noises, cvs etc.
Alright... I need someone smarter than me to explain this to me. I jacked up the front of the rig, made sure it was in 2HI and neutral and tried spinning one of the wheels. No movement on the other side. Put it in 1st. Still nothin'.

Jacked up the rear as well so that all 4 tires were off the ground. Started it up and put it into 4HI, gave it some gas and all four tires were spinning evenly (had someone else watch). Killed the engine. Left it in 1st gear. Spun one of the front wheels and the other turned in the opposite direction, just like it should.

No funny sounds. Couldn't feel any play in the CV shafts.

I'm happy, but still confused...
 

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I would Suggest getting a cheap set of stock size tires Just in case.
 

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OregonX said:
Offroad said:
OregonX said:
Does anyone know a fool proof way of checking the diff?

Jack the front wheels, put in 2wd, spin one wheel. See what the other one does, check for noises, cvs etc.
Alright... I need someone smarter than me to explain this to me. I jacked up the front of the rig, made sure it was in 2HI and neutral and tried spinning one of the wheels. No movement on the other side. Put it in 1st. Still nothin'.

Jacked up the rear as well so that all 4 tires were off the ground. Started it up and put it into 4HI, gave it some gas and all four tires were spinning evenly (had someone else watch). Killed the engine. Left it in 1st gear. Spun one of the front wheels and the other turned in the opposite direction, just like it should.

No funny sounds. Couldn't feel any play in the CV shafts.

I'm happy, but still confused...
It doesn't matter what gear the truck is in, it doesn't even really matter if it's in 4wd or not. If you jack up the front end and turn one wheel, the other should turn the oposite direction. Like I said above, it took about 8 rotations of my drivers side wheel before the pass side moved at all.

If you are turning one wheel and the other is doing nothing, then you have a diff problem.
 

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Exactly why do the tires spin in opposite directions when you turn one of them? I've known that 'unlocked' diffs will do that but I've never been able to understand why. I guess if I could visualize the gears in the diff then I could figure it out but I don't have an exploded diagram to look at.

And when you put it in gear and apply the gas to get both tires spinning in the same direction doesn't mean that we have any type of 'limited-slip' setup in the front diff, right? Isn't that just the mechanics of the front drive shaft turning the front diff/axles? The only type of limited-slip we have on our X's is ABLS, except for the locking rear diff in the OR models.
 

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Ok, so do you not understand why the tires should turn in different directions or do you not understand how the tires turn in different directions.

I'll try to explain both in as sort of a post as I can. :)

The reason you want an open diff:

When you are going into a corner, the wheel on the outside of the turn has to move further than the wheel on the inside of the turn. Because of this, the outside wheel must move faster to keep up.

If you have a locked diff both tires turn at the same speed no matter what. Because of this, when you go into a corner the outside wheel is “dragged� through the turn. This causes bad handling and really fast tire wear.


Difference between locked and limited slip diffs:

As stated above, a locked diff causes both wheels to turn at the same speed no matter what. Most lockers on the market are selectable giving the ability to turn off the locker, giving you an open diff.

There are a few different types of limited slip differentials. The most popular uses clutches. When one wheel starts to spin much faster than the other the clutches engage and transfers some of the power to the other wheel. One of the most well known limited slip diffs is “posi traction�. The new X uses a totally different type of limited slip. Instead of putting the limited slip in the diff, they use the brakes. If the system detects one wheel spinning faster than the other, the brakes grab just that wheel to transfer the power to the other wheel (called ABLS).


Why a diff works:

Inside a diff there are obviously gears. The three main parts are the ring gear, pinion gear and spider gears. The pinion gear is what is attached to the yoke (which your driveshaft attaches to), the ring gear attaches to the spider gears and is driven by the pinion. The spider gears are what actually causes the wheels to turn the opposite directions. It’s sort of hard to explain how the spider gears work and would be easier to show you a picture (I’ll see if I can find one).

EDIT:
Here is a page that explains it much better than I can.

http://auto.howstuffworks.com/differential.htm
 

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Woot! I say I need to visualize how the gears work inside the diff and you give me a link with the exact animation I need. Excellent! And now I see how the spider gears will cause one wheel to turn in an opposite direction to the wheel you're spinning by hand.

I remember my dad explaining to me why you need an open diff and how the wheel on the outside of the turn will spin faster compared to the other wheel, just like you were saying. And that's why you shouldn't run locked or in 4 wheel drive on dry payment. Not only will it cause bad tire wear like you mentioned but its also hard on the diff's gears and transfer case. If you're getting traction on the road, something has got to take up for that difference in wheel speed in turns and that thing is in your drive-line.

Now I want to take a closer look at that quick-change rear-end we run in the race car. That thing uses springs to engage both axles when you apply power but 'unlocks' when you're off the gas so it rolls through the turns better. And now that I think about it, I want to take a closer look at those Ford 9" rear-ends we run sometimes to see how they work to. (I just keep leading myself to more and more questions :cheese: )

Really appreciate the write-up and website link.

Thanks.
 
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