From the Ford 72 truck shop manual, Volume I, Part 15-30 Front Driving Axle - 441F (Bronco open knuckle).
- Install ball joints in knuckle, verify joint shoulders are seated against knuckle. A .0015 feeler gauge is not to enter at minimum area of contact.
- Install knuckle on axle yolk.
- Tighten bottom ball joint nut to 70-90 lbs-ft.
- Torque adjusting sleeve to 40 lbs-ft.
- Tighten top ball joint nut to 90 lbs-ft. Tighten nut more till castle nut and hole in stud align, and install cotter pin.
NO mention of turning (pull) torque, or fish scale.
Perhaps the most discussed topic
@jamesroney called the caster adjusting eccentrics stupid, or dumb or something like that
. Well, I decided to remove them and go back to standard preload sleeves now that I have the adjustable Trex arms.
All right, I surrender.
I did not call the caster eccentrics stupid, or dumb. I said that they are stupid AND dumb. But I didn't mean it. The sleeves are inanimate objects. I meant it about the people that use them. You are now redeemed. Don't get me wrong, they do have a place. And that is when there is a difference (error) between left and right on the housing. Also useful as camber correction.
Now ball joints. You all need to STOP reading the manual, and just listen to me. Save yourself from yourself.
What is the purpose of ball joint pre-load? How is it best measured? Why do you want pre-load? Why does the pre-load change? Why does the manual say to do it this way? Figure out the "why," and you'll understand the "what" and the "how."
I'm going to upload a cross section of a typical ball joint. The Dana 44 open knuckle uses a "push" style joint. So how does a "push" joint work? Well, there's this giant ball that sits in a lubricated pocket that holds up the axle. More weight on the axle pushes more weight on the ball, which keeps it tight. The upper joint works the same. More weight pushes on the bottom of the ball. But just how much weight is supposed to be carried by which joint? Is it 50/50? Or does one joint carry more than the other? Take a look at your King Pin Dana 30. 100% of the weight is carried by the lower bearing. The upper bearing just holds in in place. Same situation with ball joints on the modern Dana 44. The lower joint carries all of the weight, and the upper joint is just a sleeve to hold it centered. But the 1971-79 Ford Dana 44 has TWO balls, and BOTH share some of the weight. That is ONLY possible if the ball is in the socket on both joints at the same time. So what you want is an Inner-C with a precisely machined taper such that when the taper is pulled up tight, the dimension from the center of radius of the upper ball to socket is exactly the same as the center of radius of the lower ball to socket. Then when the weight of the vehicle is applied to the ground, BOTH balls are loaded exactly the same amount and there is no play or looseness.
GOOD LUCK WITH THAT!
So how do we ascertain the location of the correct taper of the inner-C with respect to the knuckle? What is the correct distance, and how would we find it? Answer = you can't. So you don't. (But it IS the correct figure of merit.) So instead, we make a bold attempt to use the ball joint as a tool or gage, and we locate the upper taper position relative to the lower position by applying a torque to a threaded sleeve. This is simultaneously idiotic, and genius. But you MUST comprehend that it ONLY works if the lower ball joint is brand new, and built to exacting specifications. The ball joint socket retainer must be exactly right, with exactly the correct press-fit, and lubricated, and then it's a "maybe." So take a look at the cut-away, and imagine that you want to load the upper ball with a proportionate weight as the lower ball. So you install the lower ball joint. You tighten the lower ball joint nut. Then you move the taper of the upper joint closer to effectively make the upper C "shorter" You load the upper joint to 40 lb-ft on a 1-1/4x12 thread. I'm lazy, and I'm not going to calculate the load, but mercifully the clamp loads are linear with torque. So a nominal 1.25x12 bolt will give you 26,600 lbs at 420 lb-ft. therefore at 10% torque, (42 lb-ft) it will provide 2,660 lbs of clamping force. It's a horrid approximation, and it presumes a lot of incorrect things about the 'k' value of friction...but let's just go with 2500 lbs at 40 lb-ft. So now we have applied 2500 lbs of force to the bottom of the upper ball, and therefore 2500 lbs of force to the top of the lower ball. BUT we are about to suck the upper ball back UP when we seat it on the taper. The giant nut on the top of the ball joint is going to allow some amount of displacement as the taper gets tighter. So we just loaded the top of the lower ball, just so that we can unload the upper ball which will unload the lower ball. But the upper C has some amount of elasticity in the forging. So the theory is that the amount of load on the upper ball will be held in the elastic regime of the inner C forging AFTER the weight of the vehicle is applied to the knuckle, and the lower ball seats on the lower cup.
If the world is perfect, then we can now measure the rotational resistance of the steering knuckle, and get a rough approximation of the Upper ball joint (lower socket) preload PLUS the lower ball joint (upper socket) friction. Notice that I called the lower joint "friction" and not pre-load, because when you put the weight of the Bronco on the axle, that lower joint stops pulling, and starts pushing. So ALL of this ONLY works if the lower ball joint is brand new, and made to exacting standards. If there is ANY axial play in the lower ball joint...this method CAN'T work.
Notice that I've said "exacting specification" about 3 times, so far. You are now relying on some guy in China, to get directions from some guy in Michigan to understand the exact level of swaging compression on the deformed steel socket that happens to coincide with the results experienced 50 years ago on a machine that was in no way similar to the one now being used to swage the joint. So it's not that the spec is not understood. It's that the spec has nothing to do with the result. So the Chinese engineer is going to do the job "exactly the same." ...but a little bit different. I call this "Chinese-same" After 15 years of successful off-shore manufacturing transision...my team knows exactly what this means. You will see this exhibited in the
@Got4wd ball joint. The spec says swage the socket with ~140 tons of load. On the machine in Cleveland, 140 tons will squeeze the outer shell so that it just kisses the ball, and makes it nice and firm. But that same 140 tons on the machine in Toronto only gets the metal to swage about half-way. So the Toronto guy says: "meets specifications." The Cleveland guy cries, and cashes his unemployment check. The supplier is clueless, and the product is useless. And then people say horrid things about China. (or Canada, or wherever...)
Can I be done now...or do you want to know how to actually do it correctly?
