Strange 8.8 question....

[Acuta73]

I have a Ford 8.8 rear-end differential in my 2003 FX4. I needed to replace my bearings.....why do I have 7.75 axle stubs? Is this normal? Can I swap to the larger stubs/axles?

/confused

 

[pjtoledo]

8.8 Ranger axles came standard with 28 spline axle shafts and differential side gears. the axle shafts and wheel bearings are the same exact shafts as used in the 7.5 rear end. the differential side gears are not.
Level II axles with the Torsion differential have 31 spline shafts and the larger wheel bearings.

the diameter of the axle tube does not have enough room for larger axles/bearings, so you're stuck with the smaller 8.8/7.5 bearings & shaft.
you can upgrade the differential to 31 splines, but will still have the smaller wheel bearings.

swapping in a modified Explorer axle is popular, they have the bigger bearings & 31 spline differential.

there is lots of info about axles, read the tech section and do some searching. and of course ask questions.

 

[RonD]

8.8" Ranger axle info here: https://therangerstation.com/tech_library/Ford-8_8-axle.shtml

Rangers used 28-spline/1.21" diameter axles from 1983 to 2011 so all years, regardless of 7.5" or 8.8" ring gear
Tube diameter was 2.80" from 1983 to 2009 for 7.5" or 8.8"
2010/11 got 3.25" tubes with disc brakes but axles were same 28-spline/1.21" diameter

Exception was the 4x4 Rangers that used the Torsen Limited Slip differential, it used 31-spline axles, these were first offered in the 2002 FX4 model, then in 2003 and up the FX4 Level II

You would have to change the differential to use 31-spline but would still have same axle diameter
You could swap in an Explorer rear end which has 31-spline and larger diameter axle

 

[pjtoledo]

and listen to RonD, so I won't have to type anymore

 

[Acuta73]

8.8" Ranger axle info here: https://therangerstation.com/tech_library/Ford-8_8-axle.shtml

Rangers used 28-spline/1.21" diameter axles from 1983 to 2011 so all years, regardless of 7.5" or 8.8" ring gear
Tube diameter was 2.80" from 1983 to 2009 for 7.5" or 8.8"
2010/11 got 3.25" tubes with disc brakes but axles were same 28-spline/1.21" diameter

Exception was the 4x4 Rangers that used the Torsen Limited Slip differential, it used 31-spline axles, these were first offered in the 2002 FX4 model, then in 2003 and up the FX4 Level II

You would have to change the differential to use 31-spline but would still have same axle diameter
You could swap in an Explorer rear end which has 31-spline and larger diameter axle

So the Torsen was an option on top of the FX4 package? Call me dumb, but reading what you wrote, my 2003 FX4 should have 31-spline....unless it was an option I don't have. Wouldn't be offended upping the axle diameter so long as I can swap my LSD carrier...discs would be a nice bonus (I'm a trucker, I don't worry about brake fade). She's getting a supercharger and air springs so I can tow a bit more than currently (my goal is a 19' Arima SeaChaser).

In the end, I was just confused as to why I had to take back the 8.8 bearing set for a 7.5 when my diff pretty clearly reads 8.8. So at least that is partially answered! LOL

Thank you!

 

[Dirtman]

Only the FX4 level 2 had the 31 spline axles. The level 2 was a upgrade package on top of the fx4 package.

 

[Acuta73]

Ok, re-reading that makes sense. Thanks.

Kinda BS I have the larger pumpkin, but the smaller axle.....actually just kinda strange. I'll live with it for now.

 

[Ranger850]

8.8 Ranger axles came standard with 28 spline axle shafts and differential side gears. the axle shafts and wheel bearings are the same exact shafts as used in the 7.5 rear end. the differential side gears are not.
Level II axles with the Torsion differential have 31 spline shafts and the larger wheel bearings.

the diameter of the axle tube does not have enough room for larger axles/bearings, so you're stuck with the smaller 8.8/7.5 bearings & shaft.
you can upgrade the differential to 31 splines, but will still have the smaller wheel bearings.

swapping in a modified Explorer axle is popular, they have the bigger bearings & 31 spline differential.

there is lots of info about axles, read the tech section and do some searching. and of course ask questions.

8.8" Ranger axle info here: https://therangerstation.com/tech_library/Ford-8_8-axle.shtml

Rangers used 28-spline/1.21" diameter axles from 1983 to 2011 so all years, regardless of 7.5" or 8.8" ring gear
Tube diameter was 2.80" from 1983 to 2009 for 7.5" or 8.8"
2010/11 got 3.25" tubes with disc brakes but axles were same 28-spline/1.21" diameter

Exception was the 4x4 Rangers that used the Torsen Limited Slip differential, it used 31-spline axles, these were first offered in the 2002 FX4 model, then in 2003 and up the FX4 Level II

You would have to change the differential to use 31-spline but would still have same axle diameter
You could swap in an Explorer rear end which has 31-spline and larger diameter axle

Didn't they just say the same thing ...

 

[Dirtman]

Ok, re-reading that makes sense. Thanks.

Kinda BS I have the larger pumpkin, but the smaller axle.....actually just kinda strange. I'll live with it for now.

Cheaper to manafacture and less material so less weight. With everything stock it's more than strong enough. Engineers don't design things for what the customer might upgrade later on.

 

[don4331]

Cheaper to manafacture and less material so less weight. With everything stock it's more than strong enough. Engineers don't design things for what the customer might upgrade later on.

I would have phrased it thus: The GAWR remained same so no need to increase size of axle shaft/differential tube/wheel bearings. Larger pumpkin is needed with the higher power (4.0) engines*.

Your comments on cost are right on money.

Explorers have higher GAWR (3,200 vs 2,700lbs) hence the larger axles.

Now, in theory, you can put 31 spline axles (they would need to be custom as Explorer and Ranger lengths are off by just enough that they won't swap) into a Ranger rear axle using Dodge parts**. But given the tube strength hasn't changed, not sure if that would buy you anything.

*Not exclusive, but generally true.

**Durango bearings/seals have the Explorer shaft id and the Ranger axle od. They are also rated for similar loads as the Ford bearings...

 

[pjtoledo]

Didn't they just say the same thing ...

yep, only 3 minutes between posting time, so we were both typing at about the same time.

 

[adsm08]

Wouldn't be offended upping the axle diameter so long as I can swap my LSD carrier...discs would be a nice bonus

You can't put a 28-spline carrier into a 31 spline axle without replacing the side gears. Most Explorers I've dealt with were LSD though. You can also put a Torsen unit in an Explorer axle.

I would have phrased it thus: The GAWR remained same so no need to increase size of axle shaft/differential tube/wheel bearings. Larger pumpkin is needed with the higher power (4.0) engines*.

Man, you better come have a talk to my B2, then. The 4.0 still hasn't blown up the 7.5 after 3 years.