Axle repair question

The mysterious orientation is simply that the crosses in both u-joints of a halfshaft assembly must be exactly parallel; has to do with the dynamics of how Hooke-type u-joints function. Additionally, some half-shafts were dynamically balenced by adding a welded weight to the light spot, so these must be reassembled the same. So when you pull the slip-joints apart, I suggest you add an indelible mark, scratch or stamp to both halves of the splined slip-joints as they separate, so the two halves can be reassembled on the same splines.

Hmmm. Well, what I've observed seems different from your description, if I understand you correctly. On these axles, the u-joints are 45 deg. off from each other. By this, I mean that if I viewed an axle assembly from one end, the center T of the u-joints are not in line, but rather one is "+" and the other is "x". This is true of both axles. I did notice a couple of metal weights (I assume) welded onto the yoke areas (non-flanged yoke) of one axle assy. On the other axle, there were added weights on one of the flanged yokes.
On the orig. axles in my car, the center T of the u-joints are alligned, ie. looking down the length of the axle, both u-joints are in a "+" orientation.
Upon closer inspection of the new 'used' axles, I found an arrow stamped into each half. These are not lined up, but are 45 degrees off from each other, so that if I alligned the arrows, the center T of the u-joints WOULD be alligned.
Is there any practical method of checking an axle to see whether it's balanced? Is it not practical to use these axles?? Any thoughts? Thanks. Paul

The crosses MUST be aligned in two planes or the halfshafts will pulsate, causing a vibration. Unlike a mis-balenced tire, this vibration will be worse the faster you go. Crosses 45 degrees off is about as bad as it can get, incidently. I think its more inportant that the crosses align than the arrows align. What may have happened in your used axles is, someone took them apart and mixed up the halves; look closely & see if things would be better if the halves were interchanged. If the car does NOT vibrate, the only thing that comes to mind is, the two half-shafts are vibrating exactly out of phase & are cancelling each other, but this cannot be good for tire mileage or component life.

Thanks Jack. I'm assuming that I should reassemble them as close to alligned as possible (hopefully w/ arrows matched), then swap out the u-joints, then take the axles to a local drive-line shop and have them balanced out. Is there any preferred location for balancing weight to be added? (I'm guessing that the previous owner must have assembled them incorrectly and then balanced them that way?!?!?) Thanks.

I'm no expert- the only place I'm at all familiar with is "Driveline Specialties" in San Jose, CA. They routinely balence driveshafts & halfshafts, make up special driveshaftsshafts for racers or fabricate our "Spicer" halfshafts and even stock "weird" parts in their shelves, such as adapter u-joints that are configured for Ford cups on one pair of crosses and GM cups on the others, for engine & tranny-swappers. I'd look in your local yellow pages for such a place, remembering that most halfshafts are not specially balenced at all, even for full-on race cars. The effort may not be needed; Id assemble them as suggrested & put them in the car & try them. No vibration means you saved $75-100. Vibration means they DO need rebalencing and you wasted a few hrs trying them- no big deal in my neighborhood.