I finally found the complete answer to upgrading the narrow rear brakes to the wider later rear brakes without replacing the entire axle housing. This applies '65 and '66, and probably applies '61 - '64 as well, since the axle housing measurements are the same. (You '61 - '64 owners can check this for compatibility by dicovering if the rear axle bearing is the same '61 - '72. If it is, which I think so, then this will work.) And, no modifications are necessary. It is all bolt up parts.

Original '61 - '66 parts: Use the original rear axle housing.
Original '65 - '66 parts: Use the original wheel cylinder (if still good) and parking brake cables. Rear axle seals are the same '65 - '72, and may be the same '61 - '64.
(Note 1: The wheel cylinders are the same '65 - '79.)
(Note 2: The rear brake cables from '67 - '79 MAY be useable. Check the donor truck.)
Replacement parts, '67 - '72: Drum and axle shafts. To make this upgrade work on a Slick, you MUST use the drums and axle shafts from a '67 - '72.
Replacement parts '67 - '79: Backing plate, shoes, all brake hardware.

The work is straight forward.
1. Remove the wheels, drums and axle shafts.
2. Remove the brake lines to the wheel cylinders. (Now is a good time to change the rear rubber brake line on the rear axle.)
3. Remove the parking brake cables from the '66 backing plates. You may find it easier to do this work with the backing plate bolted to the axle housing, but after you pull the axle shafts.
4. Remove the backing plates from the axle housings.
5. Replace the grease seals in the axle housing.
6. Install the '66 parking brake cables on the '67 - '79 backing plates.
7. Install the '67 - '79 backing plates and the '67 - '72 axle shafts onto the axle housing.
8. Install the wheel cylinder, the rest of the '67 - '79 brake hardware, and the '67 - '72 drum.
9. You are done!
(Well, I highly recommend you adjust and bleed the brakes, and then put the wheel back on, but if you figure otherwise, be my guest. )

Here is why you have to use the '67 - '72 axles:
The "stand-off" of the axle shafts from the axle housing to the face of the axle shaft from '61 - '66 is about 5/8 shorter than the "stand off" of the '67 - '72 axles. In other words, the axles from a '67 - '72 stick out 5/8 of an inch more than the earlier ones.
Here is the breakdown:
'61 - '66: Narrow axle housing, short axle shafts with a short standoff.
Sealed axle bearing, shallow backing plates and drums.
'67 - '72: Narrow axle housing, short axle shafts with a long standoff.
Sealed axle bearing, deep backing plates and drums.
'73 - '79: Wide axle housing, long axle shafts with long standoff.
Separated (two piece) axle bearing, deep backing plates and drums.

One more caveat: You MUST use the drums for the '67 - '72 axles. They are identical in every respect to the '73 - '79 drums but one: The stud holes are larger, to fit over the protruding shoulders of the wheel lug nut studs. The '73 - '79 studs have no shoulder, so the holes are correspondingly smaller. If you use drums '73 - '79, you'll warp them trying to force them over the stud shoulders.

 

It's a real service to share this useful information. Totally clueless, I ask whether this is only F100 material, or applies also to F250? Thanks.

 

It's for 5 bolt [aka 5 on 5.5"] lug patterns used in F100s & F150s.

F250s are generally eightbolt and no parts interchange between 5 on 5.5" or 8 bolt pattern rear ends.

Also it is possible to "hog" out, of have enlarged by a machinist, lug holes on the later drums, OR install later, shoulderless type, lug stude in earlier axles, as long as jobber supplies you studs with same spline size as your earlier axles' lug stud holes.
BUT I'd suggest some anti sieze compound around "shoulder" on axle flange aligning the drum on early style rear ends.

FBp

 

Thanks, FBP. I should have emphasized this upgrade only applies to the Ford 9" rear xle, not to anything else.
Hope I didn't confuse anybody.

 

Any idea what the cost for this upgrade is, taken from a junkyard?

 

Little Bro, if you have a 250 with a dana rear you should be able to do discs real easy. Check the 4wd sites. The sell brackets to hang dana 44 calipers/rotors or go with a lincoln or cadilac rear disc set from the late 70's and be able to run the Ebrake.

you'd also want the fronts disc too. Any 68-72 is a direct swap.

bob

 

wrong response

 

John Da Picker, I may be mistaken, but I believe it was 68 when the brake size upgrade was introduced. Someone can check that if it is questionable.

Using 68-72 excluding the E-brake cables (they must be retained) is a direct fit and I recommend using it with the disc brake up fit on the front. That will give you the balance of the designed system.

John

 

Talk about a blast from the past!
That is an old post - but the details are still valid, of course.

John, for rear axles, the '68 start year is correct.

Bob, the front disc brakes '68 - '72 were an option. There were several styles, and some of them are hard to get parts for today.
In '73, front discs on the F-100s were mandatory, and Ford standardized the design, which lasted for many years.
Therefore, the best solution in my opinion is to buy a '73 - '79 parts truck, and use it as a donor for both the rear and fornt brakes.

 

1968/72: Only the F250/350's had optional disc brakes (8 lug; 6.50 bolt circle).

1973 was the first year that disc brakes were available on an F100.

 

Banjo, you are correct. The only reason I suggestd the 68/72 is you don't have to deal with the spindle / draglink - tierod end issue. Which is easy enough to fix with a grinder or the larger end from a 73+.

bob