One way to restore bellhousing wishbone bolt bores

[RockHillWill]

There is always the question regarding what to do about front end 'shimmy', etc., and the most common responses are tighten bolts, adjust bearings, set toe-in, rebuild spindles, add rubber around the wishbone 'ball', weld up the ball & grind etc., etc. ALL of which are correct responses, but I have discovered the hard way that these approaches are not guaranteed to fix the problem.

What I discovered at first with the pickup and then with the panel delivery was that while all these items had been addressed, I was still feeling some slight shimmy/shake when test driving. It took me a while to figure out that the issue was in the bell housing where the wishbone pivot housing bolts were quite 'wobbly'. I had to take all the motor stuff out and look until I saw that the problem was the wallowed out holes at the top of the surface where the bolts were held in place by the small diameter cross pin that used to keep the bolts from spinning when tightening the nuts.

There are 13 drawings in the archives for this particular bolt and most of the differences are regarding the shape and depth of the slot in the top of those bolts. The lower edge of these bolts sits on the top of a CAST surface in the bottom of the bell housing. The depth of that counter bore in the bottom of the bell housing and the depth of the slot in the top of the bolt determines the amount of vertical movement of those pins. The slot in the top of the bolts is not a square cut, but rather a tapered cut, so the misfit of the bolt head to the cross pit allows the bolt to not only move up and down, but that tapered slot allows for rotation as well. It should be clear that this will allow the HARDENED pin moving and rotating in a CAST IRON bore to wallow out this hole in the bottom of the bell housing allowing movement regardless of how you fasten/tighten the wishbone pivot ball.

My 'fix' was to build a fixture to hold the bell housing upside down in the mill, machine a pilot to locate the bore in the housing and then replace the pilot with a back spot facer and pulling upward cut a smooth 3/4" diameter deep spot face in the bell housing. After dis-assembling the fixtures, you can use hardened spacers from McMaster-Carr and the pins that you are going to use and set the height of the pins to seat against the bottom of the bolt head slots.

I have done about a dozen of these and it seems to work out real well. I just did the last two of these that I intend to do, as this 'coach building stuff' that I have gotten involved with is taking up most of my time. These fixtures (less the mill collets) are for sale for $200.

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