I have ST22 and the ST75 '66 truck supplement and I don't see a whole lot on adjusting the three speed linkage. From just quickly paging through it looks like just a few paragraphs in the three speed section and a little more about assembly in the steering section.
This is probably what you need;
Transmission linkage adjustment.
In cases where gearshift linkage has been disconnected or removed, proper adjustment sequence is important.
1. Install control rods to both second and third shifter lever and first and reverse shifter lever. Set both shifter levers in neutral postion.
2. Align both shifter tube levers on mast jacket in the neutral position. Position relay lever so that gearshift control lever is in neutral position.
3. Connect the control rods to tube levers making sure clamps are properly adjusted so that tube levers and transmission shifter levers remain in their neutral positions while tightening.
4. Move selector lever through all positions to check adjustment and insure over-travel in all positions.
Note: If mast jacket lower dash clamp has been disturbed at its mounting on dash, its adjustment to the steering mainshaft should be checked as outlined in the procedure in Section 9 of this manual.
It doesn't say a whole lot more. Hope this helps.
