Dana 20 double cardan yoke to short for Dana 18?

I got a Dana 20 yoke for the rear of my Dana 18 for a double cardan yoke from Tom Woods Driveshaft. They said the splines would match up, which they do. However, it appears that the length of the machined cylindrical portion of the OD of the splined portion which fits over the output shaft (what the seal rubs on) is to short. Its about an 1/8" shorter than the yoke I took off. I can put the yoke on and tighten the nut down but the yoke keeps sliding in. It looks like the yoke should butt up against what I think is the back of the bearing, held on by the nut .

Does that make sense? Anyone had this issue before? It would seem I need to track down a Dana 18 specific double cardan yoke.
Jon

 

I ran into the same problem. I put a spacer behind the yoke.

 

What size is the nut on the back of a dana 20 rear output shaft? I put a spacer in the dana 20 yoke on my dana 18. There is not room in the dana 20 yoke for the socket necessary to fit on the Dana 18 nut, which is 1-1/4 inch across the flats, a heavy hex size. As near as I can tell the threads are 3/4-20, a extra fine pitch. I need a 3/4-20 castle nut 1-1/8 across the flats. Is that what is on the rear of a dana 20 if I order that?

 

To answer my question, in case it ever comes up, both my Dana 18 Transfer cases have 3/4-20 threads. A dana 300 transfer case and a Dana 30 or 44 pinion ( Iforget which) have 3/4 -16 threads. I needed a 3/4-20 nut with smaller size across the flats than 1-1/4". Napa part number 630-1523 is a 3/4-20 nut, 1-1/16 across the flats. That is a castellated spindle nut off something other than a jeep but it works for my dana 20 yoke on a dana 18.

That is different than what I was told by one frequently referenced driveshaft shop which said they all had 3/4-16 threads.

 

Later 18 transfer cases do share the same threads as the 20 and 300 transfer cases (and Dana 30, 44, etc.). The earlier 18 transfer cases did have the 3/4-20 threads and used a castle nut as you noted.