ford 8.8 with 9" brakes

[snab07]

Anyone ever come across a ford 8.8 axle with 9" brakes and outer bearings and seals from a7.5"? My axle seems to be one of these. My axle came from a Mazda b4000 but I'm unsure of the year. My truck is a 96. The axle tag and a visual inspection of the axle confirm that the center section is an 8.8 but it has 9" brakes and the beatings and seals are from a 7.5 any thoughts?

 

[adsm08]

The 28 spline 8.8 shares outer bearings, seals, and axle shaft diameter with the 7.5.

As for the 9" brakes, since so much of the wheel end is already the same it is possible they were swapped in a tight spot because the PO had the parts laying around.

It's also possible, if you are going solely by visual ID that you have misidentified your brakes. Finned drums is 9", smooth drums is 10", but some Aerostars had finned 10" drums.

 

[JoshT]

ADSM couldn't the 9" drums be stock as well. I thought the 10" was an option on the 8.8 and also part of the towing upgrade package.

 

[snab07]

As far as the 28 spline 8.8 and 7.5 sharing outer bearings and seals I don't think that's right because that's how stumbled on this situation to begin with. The bearings and seals are different part numbers and the ones for the 8.8 are physically bigger and wouldn't fit in my axle tube. I ended up going with everything for a 7.5 but the center section is definitely an 8.8 and the brakes are the finned 9 inch drums. I was just wondering if anyone had seen this before because I've never even read about it happening

 

[JoshT]

As far as the 28 spline 8.8 and 7.5 sharing outer bearings and seals I don't think that's right because that's how stumbled on this situation to begin with. The bearings and seals are different part numbers and the ones for the 8.8 are physically bigger and wouldn't fit in my axle tube. I ended up going with everything for a 7.5 but the center section is definitely an 8.8 and the brakes are the finned 9 inch drums. I was just wondering if anyone had seen this before because I've never even read about it happening

Sorry, but it is right. The only bearings and seals that the 8.8 ever came with were the smaller 28 spline components that it shares with the 7.5" axle, and the larger 31 spline components. If the initial parts you were sold were for an 8.8" and they were too big, then they were for the 31 spline 8.8".

Both the 7.5" and the 8.8" axles could come equipped with 9" drums or 10" drums from the factory depending on how the truck was equipped.

 

[snab07]

That makes sense. Thanks for clearing it up

 

[AllanD]

I've personally never seen a 4.0 engine/8.8" axle equipped Ranger that did not have the 10" drums as factory equipment.

There WERE 8.8" RANGER axles made with the 31-spline outers, these were the factlry bits on the relatively Rare FX4-Level2 trucks.

These also have fatter axle tubes..

Personally I would not waste time searching for one of these "Level2 "axle assemblies as they are relatively rare which in turn makes them harder to find parts (replacement axle shafts) for them.

As a note if you go to most chain auto parts stores they will try to sell you outer bearings and seals for the 31-spline axles because their parts books (and computers) have been WRONG for decades (literally)

 

[Mac]

What actually determines the size of rear break is the truck weight rating. Under 4580 lbs got the 9".
Dave