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FX4 Rear Axle - What differential 28 or 31? Locker?

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Old May 2, 2009
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Goodysgotacuda's Avatar
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FX4 Rear Axle - What differential 28 or 31? Locker?

I was wondering what differential should be in a FX4 (not level II).

I'd figure it is a 31 spline, but am not sure. I'm debating on picking up the factory axle, for $150. Would that be a locker as well?
 
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Old May 2, 2009
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I'm pretty sure its a normal 28spline. What year is it though?
LII are 31spline, but 2002 FX4 is 31spline.
 
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Old May 2, 2009
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I thought all FX4's were 31 spline, and the Level II's and later model FX4 (after they stoped using level II) had a Torsion L/S
 
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Old May 2, 2009
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It's a 2006/2007 FX4. So the torsion is a limited slip unit huh? I don't know much about how they work, I just assumed they were a sort of locker?
 
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Old May 2, 2009
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Limited slip using helical gears instead of clutches.....virtually no wear on the helical limited slips.

02 fx4, 03-07 non L2 = 28spline.

08+ fx4(or when they went to one Fx4 model), I'm unsure of spline count....I assume 31.
 
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Old May 2, 2009
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Hmm, Thats interesting. Does the Torsen have more holding power than a fresh clutch limited slip? Any better with a wheel off the ground? If I remember right you had one, and it grenaded or something didn't it?

This FX4 doesn't have much left to mess with. I'd like to get the front axle, brakes, etc out of it. But I'm not certain that I want to go through a 4x4 swap to my Edge. Someone bought the driver's seat or i'd consider the seats. It was rolled...a few times, mirrors are broken off, tails shattered, front ambers. Wish there was more to get! I'd raid the thing!
 
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Old May 2, 2009
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Torsen is comparable to a detroit true trac....i've seen one off road...and it's a tight mother. yes it slips as it is a limited slip, but i've also seen the truetrac with one tire in the air still powering the one on the ground and the truck was still moving.

I was lucky raiding a 2002 Fx4 about a month ago. Twas awesome..not much left on it now. lol.
 
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Old May 2, 2009
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That kinda sounds right up my alley. If we're pretty much 100% sure that this 06/07 FX4 is a 28 spline. I may go pick that differential up!
 
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Old May 2, 2009
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Mike....I've got both axles at my house....28spline and 31spline 8.8. I'll go take tube circumference measurements for you to confirm the spline count of the axle.

See this pics too......notice where the brake backing plate mounts to the tube....look at the tube.....


28spline...
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Size:  147.7 KB

31spline...(notice heavy 'notch')
Name:  P3230659.jpg
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Size:  123.7 KB
 
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Old May 3, 2009
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It looked like a 28 spline to me, but after messing with it for about an hour getting it all apart. I finally got one axle out, sure enough it was a 31 spline. I think the housing was tweaked, because the axles were a PAIN in the *** to slide out. Probably better off anyway that it was a 31, i bet if it was a 28, something would be tweaked in it. Sucks!

I did get the cluster out of it though, $25. I'll see if i can make it swap into my truck
 
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Old May 3, 2009
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If you can get that cluster in I'll buy your stock one for 25 + shipping.
 
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Old May 3, 2009
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Originally Posted by 04blackedge
If you can get that cluster in I'll buy your stock one for 25 + shipping.
I'll have to run it by my buddy first. He has an 06 with a stock black cluster, we'll probably trade something for it. But if he doesn't want it, I'll probably sell it.
 
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Old May 3, 2009
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In 2008 FX4 it was either a 31 L/S or upgrade to a 31 Torsen.
 
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Old May 3, 2009
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I just want it so I can LED it without having to run without a cluster, I can send you my stock one once I'm done lol
 
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