I probably could have just asked someone on here, but I need to replace my rag joint and decided a U-joint would be better. The only problem was to count how many splines are on that little shaft . So like a good little engineer I calculated it... Here is the procedure. Im sure I will catch plenty of "NERD" flack for this, but I am posting it to be helpful. So make fun all you want. The same will work for any shaft, but it is especially helpful for this shaft since it has a flat side on it, is small and a real pain to manually count the splines.

First, there are two ways to get the two measurements you need.
A) Measure the major diameter of the shaft and the spline spacing inside the mating coupler. I found this to be the easiest way to do it without removing the shaft and measuring the spline length inside a new rag joint at the AutoZone counter. Remember to make sure the vernier calipers are on the top of a spline peak when measuring the diameter, not resting between two splines. This will improve accuracy. If you cannot see, simply rotate the calipers while applying gentle pressure to the thumb indexer and observe the highest number.

B) Measure the minor diameter of the shaft by using the tip of your vernier caliper in between the spines, oriented axially with the shaft. Then measure the spacing of a single spline between the spline troughs on the shaft.

Engineering notes: The spline spacing is called a "secant". Also, the precision of this calculation will be reduced for odd spline counts due to error in the measuring of the diameter, but resolution should still be good enough for you to determine spline count.

Second, divide the secant length by the diameter. This will provide the secant angle sine.

Third, calculate the arcsine (sine^-1 on some calculators) of your result from the second step. On a calculator set in "degree" mode this will provide the spline arc size in degrees of swept arc and on a calculator set in "rad" or "radian" mode this will produce the size of the swept arc in radians (a number that represents angles in the number of Pi per half circle, eg. 3.14159 radians = a half circle or 180 degrees) The calculator mode is important for the next step.

Fourth, calculate the number of splines.
A) When in radians, simply divide 3.14159 by your result from above.
B) When in degrees, simply divide 360 by your result from above.

Obviously these are two very different numbers to divide by so you will know if you are in the wrong mode right away. For example, if you have a 30 spline shaft and you divide 360 by 0.1036 radians you get 3473.774. I hope you can tell by looking at a shaft if there are approximately 30 splines or 3474.

Also, dont worry if your spline count doesnt come out perfect. The fact of the matter is that splines do not come to a perfect point and there is space that is intentionally left in the design to facilitate assembly of two shafts. Obviously there is also measurement tolerance stacked on top of manufacturing tolerances. Simply rounding to the closest number will most often be sufficient.

If you come up with 35.5 splines for a shaft that could be either 35 or 36, your best bet is to rotate the caliper on the shaft to see where the jaws fall on the spline peaks. If one is resting between two peaks while the other is resting on a single peak, then you have an odd number of splines and the number is 35. If the jaws are each always on a single peak or always on two peaks then you have an even number of splines and the number is 36.

In the case of the mystery steering shaft, I calculated a spline count of 30.31, but I found that changing the measured secant length by +-5 mils yeilded a 2 spline difference. So I did some research on performance joints and found that standard shafts near my measured diameter are 11/16-36, 3/4-36, 3/4-30. When comparing my numbers (0.725 major diameter and 30.31 splines) it became obvious which one would be the standard for my shaft.

This is the U-joint that I ordered:
http://www.jegs.com/i/Flaming+River/...746DD/10002/-1
In order to protect it better against the elements I am going to wrap it with silicon tape and replace the plastic rag joint shroud. I will let you all know how the steering response is after it is installed. I suspect it will be slightly bone jarring, but more accurate.

-William

 

http://www.s10forum.com/forum/f178/h...ng-mod-395639/

 

Nice as the flaming river joints are you can do the same thing for a lot less $$ and a fraction of the time https://blazerforum.com/forum/showth...steering+shaft

 

I knew I should have just asked first, but doing the calculations was more fun. I got it in, but was off by one spline and my wheel was off by 12 degrees So I had to dig into it again and rotate the U joint by one spline. Now it is fantastic. The steering is so much more precise it is incredible. I guess I should expect that, going from a 240K mile rag joint to a brand new U joint. The only thing is that on grated pavement on the highway, holding the steering wheel is a bit like holding on to an orbital sander. It is a small price to pay for an overall increase in steering performance.