Steve,
Undo the tie rod ends, dismount the rack and remove the U-joint at the top of the rack shaft. Turn the rack shaft to see that it is straight and that there is no binding. This is also a great time to see to it that the kingpins and bushings are free and straight. Now reinstall the rack, leaving the bolts finger tight. Observe the column shaft and its relationship to the rack shaft. Their axes should want to intersect exactly between them. There is a tool which consists of two conically pointed stubs which fit over the ends of the two shafts and should have their extreme tips just touching when all is correct. Adjustment is by the freedom allowed in the hardware, and shims, which should still be there. The shims are available from Moss
Once you have achieved this, you will have to remove one of the elements and insert the U-joint. The idea is that there should be absolutely no binding, side load, OR bending of either shaft to get them aligned. We find this fault more often than we'd like. The procedure is outlined in the workshop manual, and I'd strongly advise you to follow that procedure exactly in order to diagnose just what has happened with your particular car.
Concerning the uneven thread count at the tie rod ends, many things are possible. First, obviously, this is an adjustment so it is implied that there is innaccuracy in the system and all its components "stacked" together. It is possiblle that even with everything in perfect condition, installed quite well in an undamaged car, you may have a situation wherein this is the case. But wait, THERE'S MORE!
More often, when we find this condition, we discover that the rack is not centered, due to earlier work not carried out properly, or due to a damage situation. Here's how to center it:
With the rack in the car, the upper column and U-joint installed, and everything working freely, temporarily install the steering wheel and turn it all the way to the right. Next, place a piece of masking tape at twelve 'O Clock. Now, counting the exact number of turns and fractions of turns, rotate the wheel all the way to the left. Now do the math and turn the wheel back to the right exactly half the revolutions you counted. You now have the rack and pinion at their exact operational center, and it's important to do so. Install the steering wheel carefully now in the exact straight ahead position. On to the tie rods and toe-in.
The professional way to proceed is to now set the wheels, free of tie rod ends, to the direct zero straight ahead position. Without professional equipment, this is tough, but the idea is to insert the tie rod ends into the steering arms after screwing them onto the tie rods just enough to slip into the arm eyes without disturbance. This is almost impossible! so just get close as you can. It'll work out in the end.
Now set the toe in. If you can, set it with reference to the rear wheels. O.K., it's time to drive the car. If the steering wheel is not on center while going straight, you need to note how far off it is, come back to the garage floor, set the wheel straight, and "trade" the adjustment of the tie rods left for right by using the threaded portion EQUALLY on the left and right, until the toe is correct, the wheel is correct, and the car tracks straight with the wheel pointed dead straight.
What happens is that over the years, little inaccuracies have crept in, perhaps a wheel was exchanged, etc. etc. Often during these, shall we say "less than professional" repairs, Folks get the steering wheel straight simply by removing it and putting it back on in such a manner that it is indeed straight on a straight road, but the rack, as you now can see, is working off center. This is bad because the racks have always been manufactured such that the hardening of the rack gear is greater in that on center position. This is done because that's where the thing will spend most of its time. In this manner, it is hoped that the wear across the entire part will even out a bit. Nice theory...
If this is confusing, I have not done my job correctly. Repost and I'll try to do better. I'm in a bit of a hurry right now, as I'm trying to get ready to take my "summer" vacation... I hope I have helped though.
Motorbill
From Lola to Land Rover, If it's British and has wheels, it's likely I've bloodied me knuckles thereupon