Front End Wobble Revisited

It was embarrassing pulling into the show and shine last week.  Hitting the slightest bump sent the front wheels into a death wobble.  I used to be able to tame the tantrum by turning the wheels sharply but last Wednesday the only option was to accelerate to more than 30 kph (not an option) or to come to a complete stop.  On Saturday I decided to fix the problem or break down and add a shock absorber between the axle and tie rod.

I had the impression that the wobble started at the right front wheel so I lifted that side of the axle with a jack and carefully inspect the linkage.  There was some play at the drag link ball cap. Either I didn’t tighten it properly a month ago or perhaps in a former attempt to fix the problem I added a penny as a shim and the repeated wobbling had cause the penny to more fully conform to the shape of the drag link cup making it loose.

Upon further inspection I noticed some looseness between the top eye of the axle yoke and the spindle bolt. The bolt doesn’t rotate in this hole and should be very tight.  I recall reading that one T enthusiast actually glued the bolt to the axle eye with loctite. Repairing worn axle eyes is an easy fix if you have access to a Stevens Reaming Fixture.  Here is what I did.

RHW_9513With the front wheel off the ground I pulled the spindle bolt. Leaving the spindle arm attached to the tie rod I moved the wheel out of the way.

The first law of reaming is, “never turn a reamer backwards”. It is natural when removing the reamer from the hole to unscrew it, don’t.  Turning it backward dulls the cutting edge. The second law is, go slow, take fine cuts. The tension screw at the bottom of the fixture is more for alignment than tension.  A sharp reamer will cut well with very little downward pressure.  The reamer will grab if too much tension is applied. Forcing it can break the brittle cutting edges. I use my right hand to turn the T handle and my left index finger to turn the screw and take up the play created as the reamer does its job. It takes more torque on the T-handle to cut the bottom threads but still use the tension screw mostly for alignment.

1)   Starting with the most worn hole first makes for better alignment. In my case the bottom threads were fine so I only repaired the top eye.

2)   Assemble the fixture by screwing in the two stabilization bars and choosing the appropriate cutter. The bars keep the fixture from canting causing misalignment.

3)   Use cutting oil. It helps to keep the cutting faces sharp and makes for a quicker and smoother repair. Blow out the chips often with an air hose. You may need to loosen and lift the tapered cutter a bit to blow out the chips.

RHW_9517RHW_9524 (1)4)   Stop and do a trial fit with the bushing to see where you are at.

5)   When you are finished the tapered bushing should sit slightly proud to the top of the axle so that when the bolt is tightened the bushing will compress and hold it firmly in place.  Check the depth often.  Reaming the hole too deep will create huge problems you won’t want to deal with.

In some cases the tapered insert will be too long.  Simply grind off the bottom of the insert so that it doesn’t interfere with the brass spindle bolt bushing.

IMG_1834Reamers6)   The tap reams the bottom hole to size and cuts 5/8” – 24 threads which will accept a special ½” ID threaded bushing. Notice that the inside threads stop short of the top of the bushing. This allows the shaft of the bolt to enter the bushing for a double fit. If the threads go all the way through the yoke the spindle bolt will not seat properly.

7)   Insert the threaded bushing with a ½” fine thread bolt and jam nut. A drop of Loctite on the outside threads will help keep the bushing in place.

It worked. After about 200 miles of driving the wheels haven’t wobbled but I have a feeling the demon won’t stay caged for long.

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