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Thursday, August 7, 2014

Setting pinion angle, for spring perch welding

My little son is helping out lifting the bare block and flywheel cover into the frame and the new engine rubber mounts. This to get the correct angle of where the engine and trans tail shaft sits.

Engine in place and the trans has been lifted in as well. Now this picture shows the angle finder in a funny spot. One should not measure the angle on top of the trans, I just left it there. But it actually showed that the the top milled surface of the block was 90.0 degrees to the trans to bell housing mounting surface and exactly 0.0 degrees or 90.0 (depending on where you measure) to the tail shaft. Exactly as one should have expected it.  

The engine proved to lean backwards by 3.5 degrees. I zeroed the angle finder at the tail shaft and proceed to un tighten the rear U-bolts slightly. Then I set the pinion at 3.5 degrees or 0.1 degrees as the angle finder was zeroed at 3.5. 

I then backed down to 2 degrees "preset". This gives the pinion 2 degrees of "climb" space during acceleration. 

However some friends recommended me not to go as far as 2 degrees preset as that would give me a total of 3.5 + 2.0 = 5.5 degrees of universal joint angle movement and that is the maximum recommended angle before one can expect vibration. As this is a stockish build i decided to back down to only 0.5 preset, which will give me a total of 3.5+0.5 = 4.0 degrees of universal joint movement.

Time for some welding


  1. Hi Jimmy
    At what angle does your prop shaft sit?
    I'm just starting on the same project and can't get my head round all these angles.
    The angles must change as the pinion climbs and falls.

    1. I should have added that this process above is only ok if you have a stock resto where the relative height between trans tailshaft and rear axle centreline hasn´t been altered with. If the truck has been lowered one should alter the angle of the engine trans to compensate for the rear axle drop.
      The main goal is to have the same angle on trans output shaft and rear axel input shaft. And as this was a stock rebuild i did never haveto take the propshaft angel into account as the height between trans output shaft and rear axel input shaft is already set from Ford designers back in 56, I just had to match the angle of the rear axle to the output shaft of the trans and then tilt the rear axle just slightly 0,5 degrees forward to compensate for some slight climb during acceleration.

      What was your build? please refresh my memory?

      If you have the engine inside the frame together with rear axle and prop shaft all set up as it should be when done (except welded spring perches) then measure the angle of the engine towards the vertical line (gravity) with an angle finder, then also measure the angle of the propshaft towards the vertical line (gravity), make sure you measure at 12 o clock on the prop shaft. Take the larger and subtract the smaller. If it comes out larger than 5,5 degrees, you might need to change the angle of the engine.

      Let me know what you turn up with and we can take it from there