I have an 85 F250. This is a work play truck. I pull an 18' soon to be 20' trailor.
I am making some changes one of wich will be a 9" rear. What are your alls thoughts on the 9" for this app.

 

The 9" is a fine axle for a half-ton truck, but it is not a 3/4-ton truck axle. If your truck is an F250, it should have a full-float Dana 60 rear axle, which is stronger than a Ford 9". Actually in '85 it could have a Ford/Sterling 10.25" full-float too, since '85 was around the year Ford changed from Dana rear axles to ones made by Visteon on the F250 and up trucks.

A full-float Dana 60 can be identified by these items: a bolt-on sheetmetal rear cover with 10 bolts around the cover and a fill plug in the cover, 8-lug wheels, and a full-float hub that sticks out from the center of the rear wheel that has 8 smaller bolts going around it.

A 10.25" full-float will have 12 rear cover bolts and no fill plug in the rear cover (it's in the side of the center section housing), with the same full-float hub sticking out the center of the wheel.

If your axle doesn't not have this center hub and instead has a flat area in the center of the wheel (usually with a dimple in the center of it) that does not stick out from the wheel center, it is a semi-float axle, which some light-duty F250's did come with. In any case, a semi-float Dana 60 or Ford 10.25" is still slightly stronger than a 9", which is also semi-float.

The 9" can be identified by a welded-on rear cover and a removeable bolt-on '3rd member' gear housing made of cast or nodular iron that attatches to the front side of the axlehousing center section. The oil fill plug is usually in the side of the 3rd member housing.

Semi-float means that the axleshaft not only transfers power to the rear wheels but also supports the weight of the vehicle, via the outter axle bearings in the end of the housing tube. The brake drum and wheel are connected directly to the end of the axleshaft flange. With this axle type, if a shaft breaks, the wheel and brake drum go with it.

Full-float means that the axleshaft only transfers driveline torque and does not support the weight of the vehicle. The axleshaft has it's own bearings inside the 'spindle' end of the axle housing, and a seperate wheel hub rides on it's own bearings on the outside of the 'spindle'. The wheel and brake drum attatch to the hub and the axleshaft drives the hub through meshing splines on the inside of the hub and outside of the end of the axleshaft. With this axle type, if a shaft breaks, the wheel and brake drum are unaffected and stay on the truck, you just lose power to that wheel (actually both wheels, because of the operation of the differential, unless it has a 'locker').

 

SoCalDesertRider, I presently have a D61, yes a D61. I do want a locker, the D61
is a pain to put a locker in. It can be done, but not worth it. I know the 9" can handle all kinds of H.P. But towing with 35" tires puts a different kind of load on things. I was planning on 35 spline shafts.But the strength of the housing is really my question.

 

Oooh, sorry 'bout the Dana 61. Might want to ask someone if a Dana 60 carrier will fit in it. If not, I would forget the 9" and find a Dana 60 full-float from an '80-'85 F250 or 10.25" full-float from an F250/350 '86-'97. The other thing about the 9" is that any one you find will have 5 bolt axles. The Dana 60/10.25" will both have 8-bolt hubs to fit your wheels.

 

D61 is just a big bummer. If I go to a bigger dana it will be a70. doesnt weigh much more than the 60. I was wanting to save weight & not have the giant pumpkin scarfing the ground off road. As for the 5 bolt pattern you can change that when purchasing new axels. Still researching THANX FOR REPLY!

 

Good luck with the project!