Ford 10.25 Full Float Axle Rear Disk Brake and Rebuild



Unfortunately I don’t have any pictures
of the rear end rebuild except the above one showing the rear disk brakes. 
The rebuild of the axle included new gears (4.56) and a Detroit locker. 
Gear setup is made a little easier because the shims to setup the backlash
are installed outside the bearings, between the bearings and the axle housing. 
Unlike the Dana 60 which has the shims installed in-between the bearing
and axle carrier, requiring the bearings to be removed to change shims. 
The hub seals were replaced with non Ford seals, which were a lot different
than the seals that came out.  In our opinion not as well made. 
I later went to Ford to price and compare replacement seals.  The
Ford seals were actually cheaper. 
If you have an early Ford axle (’90 and below) Ford now offers an “up grade”
kit, which consists of a new hub bearing, oil slinger, and seal. 
Its a little pricey but if you find your old seals leaked a lot then this
kit may be necessary.  The older hubs did not have the oil slinger
which would suggest they had a tendency to leak.  I didn’t use the
upgrade kit, we’ll see how it goes.  The only other modification was
to remove the rear sway bar,  so far in normal on street driving (no
load, not towing) it hasn’t changed handling.  If you do a lot of
hauling I wouldn’t recommend this.


Adjusting Pinion Pre Load

The pinion pre load is adjusted with a
crush sleeve on the Ford 10.25 which requires extreme force to crush (300-600
pounds of force).  Tightening the crush sleeve will require some innovative
thought on how to hold the pinion from rotating while tightening the nut. 
We used a long rod which had an eye on
one end which was bolted to one of the holes on the yoke used for the ubolts
which hold on the ujoints.  A large pipe was then placed over this
rod and another much longer pipe (4 feet) was placed over the 3/4″ drive
socket wrench used to tighten the nut.  Tighten the nut until light
resistance is felt when turning the pinion, its now time to test the pre
load.  Don’t over tighten before testing pre load.  You can use
the same method to measure pre
load (weight hung off rod) as we did with the front axle.  Measure
pre load and tighten pinion nut as necessary to add more preload, tighten
nut in small increments to avoid adding too much pre load, you can’t back
it off.

TSM Rear Disk Brake Conversion

Thinking I would save time, and not having
a home machine shop, I ordered the TSM rear brake conversion kit. 
At $300 US its fairly priced but unfortunately I ran into a few problems. 
First there are two different Ford 10.25 rear ends, they differ in the
hub to flange dimension.  TSM refers to them as “early” and “late”
models.  According to the year of my axle it was an “early” model. 
However when I installed the kit we found that a 3/8 inch spacer was required
between the flange and the TSM bracket used to mount the caliper. 
This is the same problem found in the article on the conversion in 4wheel
and off road magazine.  It would seem logical for TSM to ask the customer
to measure the distance from the flange to the end of the axle to determine
what axle they have.  However they don’t do this.  To their credit
they did send me new rotors which correct his problem, but it took about
two weeks to get them, and to install them would mean that I would have
to remove the hub from the rotor, which would mean that I should really
clean the hub again.  So instead I made up a 3/8″ spacer out of aluminum.

Another problem with the kit was the rotors
they included wouldn’t allow proper seating of the wheel studs into the
hub.  They literally fell out after being hammered in.  This
was because the spline on the studs was not long enough and would not engage
in the hub, since originally the stud did not have to go through anything
before being seated into the hub.  Ford uses an odd ball stud so trying
to find an off the shelf stud with longer splines is next to impossible
(I searched and searched).  The solution is to take your wheel studs
to a machine shop and have the splines lengthened, this is called a “knurl”. 
It should cost you about 20-40 bucks but some machine shops may be leery
to do the job because the studs are hardened, so it may ruin their knurl
tool.  In the end I couldn’t find a machine shop who could do the
job fast enough, they were booked solid into the next week.  So I
instead got sleeve retaining compound, applied liberal amounts and reinstalled
the studs, then put wheel nuts on (backwards, flat side against hub) to
hold them on tight, and left it over night.  Seems to be holding up
fine.

TSM recommends using rear calipers from
a ’78 Elderodo, these are expensive and besides the caliper you also need
the parking brake hardware that attaches to them.  I did buy a set
but couldn’t locate the parking brake hardware.  So I returned them
and went for the slightly less “legal” approach.  A set of front calipers
from a ’80 Chev 1/2 were used (a lot less, about 35 CDN compared to 180
CDN for the others) with brake hoses from a ’78 Pontiac Perisian were used.

Parking Brake

Because I went with the regular front
calipers on the rear another method of locking the brakes was needed. 
A Jamar wheel lock was used.  These are hydraulically activated and
do not require electrical power like the line locks used by drag cars. 
They are also much cheaper.  I mounted it in the cab about the same
place as the original parking brake.  A line was run from the rear
wheel master cylinder outlet to the wheel lock, then back to the line running
to the rear wheels, requiring no cutting of lines.  The lines were
run through the holes in the firewall which originally were the holes for
the bolts which held on the parking brake pedal mechanism.  They were
enlarged slightly with a 1/2″ drill to fit the nuts on the lines through. 
The female fitting on the master cylinder is 5/16″ but with a 3/16″ line,
requiring an adapter since 3/16″ brake lines come with 1/4″ fittings.

Front to Back Track

After installing the rear disk brakes
we put the wheels on, or at least tried to.  With the disk brakes
the wheel studs stick out much farther, since there is no brake drum to
clear, or another way to look at it the wheel sits farther in.  My
rims came with closed wheel nuts and weren’t long enough to hold the wheel
on and stock wheel nuts would not work with the aluminum rims.  So
on when the stock tires, but now we noticed an even bigger problem. 
This combined with the slightly wider front axle lead to a difference of
2 1/4″ per side in axle length.  Meaning the rear tires were inward
2 1/4″ more inches than the front.  Not ideal at all.

To kill two birds with one stone I ordered
up a set of 2″ wheel spacers from Performance Wheel, this will bring the
rear wheels out two inches and allow me to use my wheel nuts.  The
down side is their cost, $195 US, and with such large wheel spacers you
must first bolt the wheel spacer to the hub, then bolt the wheel to the
spacer.  The spacer comes with new studs pressed in.  This means
that you must cut off the original studs (to the hub) so they don’t protrude
past the spacer.

That’s it.

More…
Dana 60 Rebuild,
Rebuild of Dana 60 Including Detroit Locker,
1986 – 1996 F-250 Dana 60 Conversion,
Ford 10.25 Full Float Axle Rear Disk Brakes and Rebuild,
MileMarker Winch Installation.

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