1971 Body/Chassis FSM

1971-74 F Engine FSM

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Rebuilding the Vacuum Shifter

The first owner of this truck converted the t-case to a manual, floor mounted shifter. I decided to convert back to the original vacuum shifter just for the retro coolness of it! I had all the levers, vacuum switch, hard lines and cables but was missing the actuator. I scored a unit from a fellow IH8MUD member for cheap. Let's start tearing it down.

Fig. 1

Left Side

Fig. 2


Fig. 3

Right Side

  1. Fig. 1-2 show the unit as received. It was a bit dirty but upon testing by applying vacuum to each port it worked smoothly.


Fig. 4

FSM Drawing

Fig. 5

Side Cover Removal

Fig. 6

Shift Lever

Fig. 7

Disconnecting Lever

Fig. 8

Pulling Pin

Fig. 9

Broken J-Bolts

  1. Fig. 4 shows the FSM diagram of the vacuum shifter for reference. I suggest you print it out for easy reference.
  2. Remove the 6 8mm x 1.25 bolts and lock washers holding the side plate on. Insert a putty knife in the seam to pry the cover up. The top cover holds a dowel pin for the shift lever to pivot on so be careful when prying it up! See Fig. 5. This reveals a very simple mechanism. See Fig. 6 Remove the dowel pin.
  3. After removing the dowel pin Refer to Fig. 7 and remove the cotter pin and washer holding the shift lever to the diaphragm push rod. Now you can pivot the shifter up and pull the pin out. See Fig. 8.
  4. Use a 10mm wrench and remove the J-Bolts holding the top diaphragm housing cover on. If you are lucky they will come off easily. All my nuts came off but two of the J-Bolt shafts had corroded to the housing. I had to cut the J-bolt shafts with a Dremel tool and a cut-off wheel. See Fig. 9. I lucked into another complete vacuum shifter from which I borrowed two J-bolts. These could easily be made from some long 6mm x 1.0 threaded rod heated with a torch, bent to the proper shape then cut to length.

Fig. 10

Diaphragm Exposed

Fig. 11

Push rod Seal

Fig. 12

Screw Plug

Fig. 13

Shift Fork Retaining Nut

Fig. 14

Shift Fork Removal

Fig. 15

Felt Washer Removal

  1. Once the top diaphragm housing cover is off you can see the diaphragm See Fig. 10. Pull it out carefully, the edges tend to stick. Inspect it with a bright light behind it to see if it's cracked. Don't be tempted to put any kind if dressing on it. Fig. 11 shows a close up of the seal the diaphragm push rod rides in. I could not figure an easy way to remove this seal so left it in place. This meant I had to paint the main housing instead of powder coating it.
  2. Next use an adjustable wrench and remove the large nut and copper washer shown in Fig. 12. This reveals a smaller nut with a cotter pin and washer. Remove the cotter pin, nut and washer. See Fig. 13.
  3. Push the shift shaft as far to the left as possible. You can now remove the shift fork as seen in Fig. 14.
  4. Use a dental pick to remove the felt washer as shown in Fig. 15. Wash the felt carefully, reshape it, dry it, then oil it and put in a plastic bag for later reuse.
  5. I masked off parts of the main housing I didn't want to sandblast then sandblasted the housing and covers.

Fig. 16

Powder Coated Parts

Fig. 17

All Assembled

Fig. 18

Mounted to T-Case

  1. Next I primed and painted the main housing using Hammerite paint and powder coated the covers and bolts,nuts and washers. See Fig. 16 for the completed parts.
  2. Since this is so simple I'll not go into great detail about the reassembly. Just use a bit of grease on the shafts when reassembling.
  3. Ok so now find the square gasket Fig. 18 shows the completed unit attached to the rebuilt T-case.

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