My technique for spindle bushing replacement

Posted by Reid Welch on November 16, 1999 at 22:47:35:

In Reply to: Spindle Bushing Replacement posted by Alex Joyce on November 16, 1999 at 16:22:41:

I forget how lucky I am that my axle yokes are in perfect condition. If axle yokes are damaged, as Mark and David describe below, then better send your axle to Mark for remedial repairs.

But, my yokes are A-1. The thrust surface (bottom side of upper yoke) is smooth as glass and true- no wear. Maybe I hand-lapped it fifteen years ago; I do not recall now. Yes, slight wear ridges can dressed off, being very careful to maintain the face perpendicular to the bolt line and parallel to the upper face of the lower yoke. It can be done by hand using a lot of care. Ideally, the finish should be as smooth as a crank journal, for that small area supports the weight of the car via the top of the bronze bushing. If the steel is rough chewed, it will bed down into the mating surface of the bushing, if not chew and keep chewing.

My old bushings- about 4k miles on them had no problem with the thrust surfaces. Only a few thousandths of wear. The steel, still perfect.

Presuming that all is well with an axle: smooth yoke, intact threads, remove the old bushings from the spindle body. For a precision job it probably pays to obtaining new, hardened and ground spindle bolts- get them if the old bolts are the least bit rough or imperfectly round. Only ground bolts are likely to be round and uniform along the whole length. I even like to polish the spindle bolts with tripoli on a buffing wheel. Smooth, smooth, smooth. The new bushings-not yet mounted, should be a very nice slip fit on the spindle bolt- with room only for the oil film.

Traditional mounting: The bushing, oversized on its OD, gets squished to a smaller ID, or out of shape, or both, when the bushing is force fitted into the spindle body.

The bolt no longer fits through- it jams because the bushings are tight and mis-aligned. Line reaming corrects the fit. It is done with special, long reamer such as the one Mark owns. The reamer makes a straight, round hole through the two bushings. The hole is slightly larger than the bolt diameter. Factory clearance spec is .003", which seems wide. But with rolled-steel bolts such a clearance may be necessary just to get the bolt through.

My method: The new bushings, yet unmounted fit the new bolt just so nice. A shame to lose that, especially if no reamer is handy (anyway, it must be an aline-ream job)-

I turn down the OD of the unmounted bushing by about .005", or until it is a very easy slip fit into the spindle body. The bushing is so loose that it may even rock a slight amount.

Next step is to measure the difference in space between the yokes and match that to the spindle arm with bushings slipped in place. The new bushings thrust collar is thicker than the old so one or both bushings must be faced down on the lathe. I prefer to leave the upper one alone, and do all the facing down on the lower bushing. That way any slight deviation from squarness in the cut does no harm- the unmolested upper bushing has it's collar exactly square with its bore.

Having faced down the lower bushing to where the spindle body will just slip into the yoke, it is time to secure the bushings into the body.

With the parts scrupulously clean of oil, butter some Loctite 272 or similar anerobic stud mount onto the upper bushing OD and the underside of the thrust surface. Slip the bushing, with the bolt inside the bushing, into the spindle arm and get it seated with a light twist.

Immediately, slip the lower bushing DRY into its hole. Rotate the bolt by hand. If there is any binding, rotate either or both bushings to where any slight binding is minimized. If your OD cut was true and adequate, there will be no binding.

But if there is a touch of tightness, when the lower bushing (still unsecured) is rotated to its best spot, mark that position with a Sharpie pen for the next step.

Withdraw the lower bushing, butter bushing and hole with a film of 272 Loctite (Napa) and reinsert the bushing with a light twist, orienting again to your Sharpie mark.

Let the cement set up for a half hour. I heat the spindle until it is just hot to the touch. Heat cures the Loctite much faster-in minutes.

Withdraw the bolt. Try the spindle body in the yoke again. Perfect fit there.

Now, test the bolt for fit in the Yoke, without the body. The upper yoke has a smooth hole which should be a perfect, no-shake fit on the bolt. But it will be loose to some extent. If the looseness is really an hugely wallowed hole, send your axle to the machine shop. If the looseness is on the order of .010, make a shim collar out of shim stock. It need not be tight. The last remaining looseness will be taken care of another way:

Loctite again. See that the oil hole communicates with the bushing junction, and not just way up in the yoke area where the oil would be trapped. If this is a problem, grind a shallow lengthwise slot in the bolt from the oil hole down to the bushing area.

Install the spindle body and carefully, carefully run in the bolt. Your parts are all still very clean and dry- no oil. So take care not to snag the bolt threads on one of the bushings. Light tapping helps line things up. Screw in the bolt by fingers if at all possible.

Important part: As the bolt gets close to home, while the head is still about 3/8" or 1/4" from seating, take your super Loctite and squirt a couple drops on the exposed shank below the bolt head. Continue screwing in the bolt. Then immediately screw it back out a few turns to be sure of distributing the viscous Loctite into that loose junction of bolt and yoke. And run the bolt right on down. NOT tight. Just seat the head. The spindle body should rotate with only minor drag at this point.

What happens here, is the Loctite soon hardens and makes the bolt absolutely immobile. Not only is this good for the goal, but it prevents any possibility of further axle yoke wear. The joint is sealed from water and movement 100%.

Now, treat the bottom of the spindle bolt- the threaded end. This is different so use a different kind of Loctite- the "wicking" green colored grade. First, though, fit the castle nut in place. Turn it down to where it beds. Turning tighter yet will actually pull the yoke closed a tiny bit, enough to bind the spindle body. Don't bind it hardly at all. If the castellation won't line up with the "right" adjustment, reface the nut until it does. Take off the castle nut for the next step. Castle nut is OFF at this time. Apply wicking Loctite (or equivalent brand) to the bottom of the yoke so the stuff sucks up into the threaded end of the bolt. Wipe off the excess. Let it set up (heat speeds the cure) NOW run your castel nut back down, to the castellation you chose earlier. Cotter the nut, and apply another liberal dose of green Loctite to the nut- both the threads and to the _base of the nut_ at the yoke.

These anerobic sealants cure very hard, and very permanent. In this job we have used them to lock parts which are under a great deal of stress and hammering vibration.

Now it is OK to add oil. Because the joint is new and tight, apply a dose of penetrating oil first. Let it seep in and work the joint until some oil begins to seep out the lower bushing. Now fill either with your favorite oil- or use the grease fitting mod that Ted described last week. The finished job will be better than factory new. And probably longer lasting too. The joint is absolutely firm, yet after the first drive will be absolutely free. Good spindle joints go a long way: Make the steering feel better and safer and true up the camber, provided the axle is not bent or the original hole position "lost" to horrible wear.