A buddy and I installed a Red Head steering box on my '78 F-150, and the pitman arm doesn't slip on as far as it did on the stock box, about 1/4 inch less, with the shaft nut tight. The arm is now probably 3/8 inch from the bottom of the box, and you can see the top of the splines on the shaft. The nut is fully threaded on, but there are not threads sticking out - is that ok? I don't like it bc that's not how it fit on the other, but if I'm assured that it's ok, then I'm ok. Thank you.

 

Here's a picture of mine, fits about like OEM box did. This is a '78/79 style pittman arm on my '77 Red Head box (same box '76-'79 on F-150), I swapped over linkage in 1986 but just put RH box on Dec 2012. There is a wide space at 4 places around the shaft and a double wide spline in the pittman arm that must locate there (or vice versa?).

 

I was going to guess not aligned with the keyways as well. If you torqued it down and it' is not aligned properly you may have hurt the spline, so look it over real good if that is the case before you put it back together.

 

I suggest calling Redhead to see what they say. From everything I have read about them they will gladly advise you on this situation.

 

This makes me feel better - this is exactly how mine looks. I'll check with Red Head and see what they say, too.

 

That one above in my pic is correctly installed, there really are only 4 directions that the pittman arm will go up on the shaft far enough to let you thread the nut with washer, and of those 4, only one works when mounted on the truck. You can't put it on with the arm towards rear or right or left, the steering box shaft does not go 90 degrees right or left either. If you miss the wide spline with the wide slot, it simply will not go on far enough to let you put the nut on behind a washer.

If it looks like that one picture .... just torque it now .... 'cause it's right!