Front Disk Brake Conversion - 1968 1100 Travelall
By Jim Grammer
Important note:
This article is a report on the conversion I performed. I’m not instructing or advocating performing this work on your vehicle. Vehicle brakes are a critical safety system. Brake failure can cause serious bodily harm or death. Working on and modifying brake systems requires competent mechanical skills, if you’re not 100% sure about yours, please leave brake work to others. Neither the web site or myself can be responsible for your use of this information.
Background:
The IH 1100 model 4x4 became available in 1964 and was the first offering of an All Wheel Drive truck in the half ton range. A Dana 44 front driving axle with closed knuckles was used from 1964 until sometime in 1973 model year production, when a change was made to the open knuckle Dana 44. The closed knuckle axle was basically the same unit that had been used in 120/1200(non-HD axle) models since 1956, with the biggest difference being wheel hubs and brake drums using a 5 lug on 5.5" bolt circle. Staring in 1964 the standard front brakes were 11” x 2”. For the 1100B in ’66, they were upgraded to 12” x 2”. MT-118 shows codes and parts listings for both the 12” x 2” and the 11” x3” on the 1968 1100C, although I have never seen the 11” x 3” brakes installed on a ’68. From 1969 to the introduction of front disk brakes in 1974, the standard front brakes were 11" x 3" drums. The upgraded drums made a significant improvement in braking performance, but are not as powerful or fade free as properly sized disk brakes.
The 11" x 3" brakes should be a direct replacement for the 12" x 2" units, however the 11" brake mechanism is not a standard Bendix style and may be difficult to locate parts for. For the amount of work required and the limited improvement in braking performance, it made more sense for me to swap in disk brakes.
Goals:
Install disk brakes for greater braking performance, using commonly available parts.
Retain the closed knuckle design front driving axle(I prefer the sealed knuckle design and the adjustability of the king pin assembly).
Retain the stock 5 on 5.5" wheel lug bolt circle.
Minimize any increase in track width.
Minimize required fabrication.
Parts list:
I experimented with several possible combinations of parts, including GM 1/2 ton, full size Jeep, and Ford F150/Bronco, even considering Scout II Dana 30 spindles and hubs. I ended up using:
Stock IH Dana 44 front axle(knuckle to knuckle), and the stock inner/outer driveshafts.
1972 GM 1/2 ton ‘small bearing’ spindles from an open knuckle Dana 44.
1978 Ford F150/Bronco hubs/rotors – I believe that any Ford ½ ton with a 5 bolt spindle is a donor.
Chevy/FS Jeep 1/2 ton disk brake caliper mounts(AKA backing plates).
Chevy 1/2 ton brake calipers.
1975 Chevy 2WD 1/2 ton pickup brake hoses.
Scout II disk brake master cylinder.
Spicer(Chevy issue) front wheel locking hubs.
Modified spindle bushings(McMaster-Carr P/N 6391K438) and thrust washers(McMaster-Carr P/N 6906K525).
'Flush' style pipe plugs for the knuckle lubricant fill holes(McMaster-Carr P/N 4534K44).
Here is a pic of the major components:
Note: It is also possible to do this conversion using the stock spindle and Scout II rotor. The Ford hub is too large to fit the opening in the Scout II rotor, so either the hub needs the O.D. turned down or the rotor needs the I.D. turned larger. Both modifications are simple tasks for a machine shop, and the hub can be turned on a standard brake lathe if available. This combination on the stock spindle will result in spacing that puts the caliper almost all the way outboard on the locating pins. There should be no problem with this as long as the brake pads wear evenly, but I preferred to have the caliper centered on the rotor. If the stock spindle is used, there is no need for the modified bushings/thrust washers.
Installation notes:
I used the factory shop manual as a reference for the general rebuild and adjustment of the steering knuckles. Please see John Donnelly’s excellent article in the May 2004 issue of the web site for more details. Note that the rubber seal and felt wiper for the knuckle is the same for all 'small ball' Dana 44's, and other closed knuckle Dana axles including early Jeeps.
While the knuckle is off the axle, I installed the Chevy spindle and brake caliper mounting plate(clamped the knuckle in a big vise, holding it across the flats on the steering arm). Installed the caliper on the mounting plate, and noted that the knuckle needed to be ground for caliper clearance in 2 places. One is along the back flange of the knuckle where the felt wiper bolts on. The other is the raised boss where the knuckle lubricant fill hole is located.. The back flange needs a 'dished' area ground out just deep enough for the rounded edge of the caliper to clear. I used a half worn out grinding wheel on an angle grinder to minimize the grind radius. The filler hole boss can be ground to a taper on one edge, just enough to clear the caliper plus a little to allow for flex at the caliper mount.
Here are 2 images of the ground areas:
I installed the flush style knuckle lube filler plugs at this time and ground the tops flush with the knuckle surface. As the knuckles wer re-installed on the axle, clearance was checked between the inside end of the plugs and the axle ball. A fair amount of material was removed from the plug to ensure that it clears the ball throughout the entire travel of the knuckle. I left a broad radius on the inside face of the plug, and made sure not to grind through into the bottom of the hex socket! An alternative to this style plug would be a standard hex or square plug, ground flush on the outside and then slotted for a big screwdriver.
The knuckle was cleaned thoroughly, including all threaded holes. Spindle mounting bolt holes were chased with a high quality tap and completely cleaned in preparation for Loctite.
The stock axle shafts were retained, in part because the outer axle shaft is not interchangeable with an open knuckle style shaft. The stock outer shaft rides on a bronze bushing in the stock spindle, and the shaft diameter at this point is larger than the I.D. of the standard 2110 needle bearing used in open knuckle Dana 44's. The needle bearing in the Chevy spindles needs to be removed and replaced with a bronze bushing that matches the stock axle shafts. The stock bushing from the IH knuckles does not fit the Chevy spindle, but the bore for the needle bearing on the Chevy knuckle is 1.625”, which is a standard O.D. for bronze bushings. McMaster Carr part # 6391K438 has the correct O.D. and I.D(1.375” ) for this application. I had the length turned to match the 2110 needle bearings. These bushings are pressed into the spindles with the faces flush to the spindle surface.
When replacing the stock flanged bushings with a straight bushing, a thrust bearing is needed to replace the thrust flange on the stock bushing. McMaster -Carr part # 5906K525 was used, with the I.D. turned to 1.375”. These are 1/8” wide, and can be stacked to space the axle position in relation to the knuckle. I bought a few extra for this purpose. The thrust bearing facing the outer axle shaft needs a bevel turned on the edge of the I.D. for clearance(the axle shaft has a small radius in this area). All the machine work was handled in about 20 min. on a manual lathe.
With the knuckles back together and properly adjusted and the axle shafts installed(only the beveled thrust washer for the initial setup), I installed the modified Chevy spindles temporarily, then set up the wheel hubs and bearings(adjusted out any play, but locknuts aren't required). This is when I decided how thick the axle shaft thrust bearings would be.
The Chevy spindles have a deeper recess on the inner face where the axle shaft goes through when compared to the stock IH spindle. In addition, the stock outer axle shaft may not be long enough to allow the use of some styles of locking hub in the Chevy spindle. This is due to the thickness of the splined driver portion of the locking hubs. I tried 2 different styles of IH/Warn OEM locking hubs, one fit and the other didn't. I ended up using a set of Spicer(Chevy) hubs because they were already clean and lubed, and they fit fine.
Next, I installed the locking hub splined driver and snapring. Threaded a 7/16NF bolt into the axle shaft end and pulled the axle shaft out as far as it would go. Confirmed that the splined driver was fully seated, and measured the clearance between the inside face of the snapring and the outside face of the splined driver. This is the additional thickness of thrust washer added between the spindle and outer axle shaft. This step ensures that the inner axle shaft has as much engagement as possible in the differential side gears.
Note: in my installation, the inner axle shafts have approximately 1/8" less engagement in the differential side gears than stock. I considered this acceptable for the type of use this truck will see.
With the final setup made and the axles installed, the spindles can be installed with the brake caliper mounting plates. I used new Grade 8 fasteners and Loctite 272 for spindle installation. The wheel hubs with rotors were installed and bearings adjusted, then locking hubs. Brake calipers were mounted, and hoses installed. I found that front brake hoses for a '75 Chevy 1/2 ton 2WD fit the existing frame mounted flare fittings on my '68, and will allow for 2-3 inches of lift in the future. I have information indicating that a flare fitting adapter may be required for later model trucks.
Here are 2 pics of the installation, less locking hubs. Note that I fabricated a support strap for the ‘dust guard’ on the brake caliper mount. This is a piece of ¾” x 3/16” stainless strap stock, bent and drilled at the ends for mounting, with a 90 degree twist for everything to line up:
I used a Scout II master cylinder because I had one handy, and the 1.125” bore matches that used in power-braked GM ½ tons from the ‘70’s and early ‘80’s. The stock junction block was not changed. It is important to make sure that the pressure differential switch in the junction block is not forced to one side while bleeding the brakes. The pedal is high and firm, with good braking action. All 4 wheels lock at about the same time on loose surfaces. Since this is a Travelall with more weight on the rear end than a pickup, a proportioning valve might be needed on a pickup.
Results:
Greater braking performance, spare service parts readily available.
Closed knuckle retained, total increase in track width of 1"(66" to 67" across wheel mounting surfaces)
