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Converting FJ-40 front drums to disk with minitruck parts

 

I chose to use Toyota pickup (minitruck) parts to swap onto the front axle to replace the original drum brakes.

 

'81 through '85 Minitruck Parts list (Basically everything from the knuckle out):

  • Steering knuckle housing
  • Spindle
  • Wheel hub/bearings
  • Steering arms
  • Brake backing plate
  • Kingpin bearings
  • Knuckle seal kit
  • Inner axle seal
  • Birfield joint
  • Locking hub
  • Nuts, Bolts, Washers, Cone washers, wheel studs
  • Calipers and pads from a V6 minitruck
  • (optional) Master cylinder from V6
  • (optional) Brake booster

 

Other parts:

 

Special tools needed:

  • Angle grinder
  • Toyota SST for setting knuckle preload
  • Torque wrench
  • Brake line flare tool (for installing proportioning valve

 

 

Procedure:

    1. Drain the oil in the front axle, jack the truck up, put the axle on jack stands, and remove the wheels.
    2. Remove the old parts. Cut the brake line and remove the tie rod and then remove the face of the locking hub (or drive plate) and remove the snap ring on the axle shaft.
    3. The easiest way to get everything apart is to loosen the nuts on the steering arm and bottom plates which should allow you to pull the entire old knuckle/brake/wheel hub assembly as one piece.
    4. Next, clean up the end of the housing using shop towels and brake cleaner and remove the inner axle seal (rides around the axle shaft at the end of the housing). You may also want to take a wire wheel to the outside of the "ball" to remove any rust.

    5. Next, because we are using birfields from a minitruck, we must grind on the housing to get the larger/stronger birfield to fit. You will need to grind a little off of the top and bottom directly to the outside of the kingpin hole. Test fit the birfield periodically to check your progress. Keep in mind that you need to go about 0.040" over to compensate for how much the ball compresses when the knuckle is torqued down.

  1. Drive out the top and bottom kingpin bearing races with a brass punch. Install the new races.
  2. Calculate knuckle shim thickness and set bearing preload using Toyota SST.
  3. Install knuckle and torque to spec. Check knuckle bearing preload with fish scale. Install wiper seals on back of knuckle. Install inner axle seal
  4. Install spindle, hub/rotor assembly.
  5. Install locking hub and caliper.
  6. I chose to do away with the backing plate for the rotor along with the little brake line bracket with the short section of hard line. To remove the backing plate you must keep the inside portion of it to keep the spacing of the components correct.


  7. I used Napa #38878 for my flexible brake lines. I probably wouldn't do it the same way again. I would keep the short piece of hard line from the
    caliper and the bracket on the backing plate so that the brake line is actually "locked" from turning in the caliper. My brake line setup is commonly used without problems, but it seems a little hoaky because of this.
  8. Install the proportioning valve on the line that goes to the rear brakes. You will need to get the fittings and flare the tubing to install it. I chose to install it right next to / under the booster. I bought a short section of already flared tubing with fittings at AutoZone so that I would only have to flare one end.

  9. Wheel selection is important with the V6 calipers. You will need a wheel that has nothing protruding out the back (such as an aluminum wheel, or a wagon wheel without a lip stamped out the back).

 

 

Optional: V6 master and minitruck booster

I chose to use a booster that I had laying around. It is from an '89 4 cylinder 4runner. The master cylinder is from a '95 4runner with a V6. Everything bolted right up and took only minor adjustment to get correct. The brake lines even ended up in the right place on the MC without bending the lines!

Enjoy!

Andy Zook

www.andrewzook.com

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