FX4 Axle code
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I have a 8.8 but with 3.27 gears and the 27 spline axle but i want to replace the rear axle with an 8.8 from a fx4 because it has the 4.10 gears limited slip gears and a 31 spline axle i already got a dana 44 strait axle from an early bronco with 4.10 to mount in place of my twin traction beam dana 35
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Factory Explorer 31-spline axles can be found with either open or Traction Lok. The problem with those is that they don't work in a SOA Ranger app without welding on perches and shock mounts. Not impossibly difficult but not bolt-on either.
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FWIW, these are the characters from the tag from my 2003 FX4 Torsen 31_spline. Some of them may be coded production info or may differ by year, so don't necessarily expect to find an exact match.
N313L
4L10 88 3E15
and it has the lubrication tag:
75W140 SYNTH
OIL ONLY
The second tag is a dead giveaway because, on Rangers, only the Torsens specify 75W140 synthetic lube.
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Here's an easy check that can be done without referring to axle tags or markings. Measure the diameter of the axle tube between the spring perch and the diff housing. A 31-spline Level II axle tube is about 3 1/4" diameter and a non-LII is something like 3".
If you don't have a caliper or micrometer handy to measure the diameter, wrap a string around the tube and mark the circumference. Then transfer the string measurement to a tape or rule.
A 31-spline should be about 10 1/4"
A 28-spline should be about 9" ~ 9 1/2"
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Be very careful of any 2002MY Torsen-equipped Ranger axle because there was a safety recall due to the Torsen diffs fragging. Replaced axles have a special tag on them, purple IIRC. Those warrantied axles should be OK and Torsens in FX4s assembled after January 28, 2002 should be OK as well. The later good axles probably don't have the purple tag.
Here's the problem: Since the early failures were reported on manual FX4s, Ford warrantied the axle assemblies on the manual trucks ONLY, choosing to NOT recall the exact same Torsen diffs in the early 2002 automatic FX4s. Predictably, IMO, the suspect diffs in the automatic trucks have also been known to fail over time. Obviously, any of these early Torsen diffs are to be avoided.
ALL FX4s, manual or automatic, assembled after January 28, 2002 came with the updated good diffs. If you have access to the axle donor, you can look at the build date on the door jamb. Or, if you know the VIN of an early manual donor, a Ford dealer can tell you if the axle was ever replaced under Safety Recall #02S32.
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The second tag is a dead give away, yes. But if the tags are gone, you can visually identify it as well...without pulling the cover off the axle. Take a peek at the end of the axle housing on the backside of the brake flange....
Take a look at these pics....
28spline
31spline (note the pretty decent step down)
The bearings outer diameter is the same between 31spline and 28spline. To make up the difference, the size of the axle tube diameter is visually stepped down compared to a 28spline.
Also, if you see the donor vehicle, you can pretty much figure it out. 2002 Fx4, 2003+ Level II, select 08-09 Fx4's. Axles are super rare...hell the trucks are super rare period.
Take a look at these pics....
28spline
31spline (note the pretty decent step down)
The bearings outer diameter is the same between 31spline and 28spline. To make up the difference, the size of the axle tube diameter is visually stepped down compared to a 28spline.
Also, if you see the donor vehicle, you can pretty much figure it out. 2002 Fx4, 2003+ Level II, select 08-09 Fx4's. Axles are super rare...hell the trucks are super rare period.
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