This item may border on the trivial, but posting the web page is far easier than researching the answer.

At 08:34 AM 4/27/06, Mike Michael wrote:
"Can you tell me the diameter and number of teeth on the MGA steering u-joint?"

Counting those damn splines has to be the challenge of the century. I have tried to do it on a few prior occasions and could never get the same number twice. But now I have vowed to succeed at any cost. So I got on my close up reading glasses, got it under a bright light, and took a needle file along. I filed a bright corner on one spline near the bolt notch for a starting reference. Using thumbnail for a pointer and place holder I counted up to 10 splines, then stopped to file another witness mark, and re-counted a couple more times to be sure. Even at that I filed the wrong spline once, but managed to catch it with a recount.

In the end I count 49 splines. The diameter over the apexes measures 0.744". I suppose it's supposed to be a nominal 3/4 inch spine.

Serrated Shaft Ends - SAE J500 Click for 248-KB pdf file

But of course four years later it turns out I'm wrong anyway. On someone's advice I now count again using white tape and a fine marking pen to tick off every 5th spline. Sure enough, it's 48 splines (not 49). Two different rack pinions measure .742 and .744 diameter over the spline crests. Someone else has measured .747, but I suppose it is all within the standard tolerance range as long as it has 48 splines. All's well that ends well, as I stand corrected. Find the same splines on the steering rack pinion shaft, and on top and bottom ends of the steering column shaft, as well as female splines in the steering U-joint and the steering wheel hub.