Am doing a TH400 to M20 swap on a 72 vert. The particulars are:

Stock '72 8.5 rear end
M20 27 spline output shaft.
Used OE TH350/MT shaft - solid w/no rubber inserts and with the front 3" and rear 12" taper of the tube.

Bought the AC Delco U Joints - P/N 45U0108 (GM#89029290) and the joint seems to be too wide. Fits in the holes nicely but I can only get one of the internal snap rings in place. When I put the one clip in, the other bearing cup sticks out about 3/16th's of an inch and if I push it in any further, it seems like it bottoms out against the cup (the joint starts to bind)

The yoke and two ends of the driveshaft have a width of 3 9/16" (to the outside of both faces) What is the right U joint to use? The Rock catalog makes no distinction I can see between the TH400 U Joint and the M/T U Joint - what am I missing?

 

You're missing the needle bearing that fell into the bottom of the cup as you hammered it on.

Remove the cup and check, then reassemble, with plenty of grease to hold all of the needles in, and try again.

- Eric

 

I agree Sounds like a needle bearing got dislogged and is at the end of the cap.
Put the u-joint in a vise and take a measurement before installing and see what it measures compared to the u-joint width in the drive shaft / slip yoke.

Jim

 

Thanks for the replies - unfortunately, it turned out to be something a little more complicated. Apparently at one time, this shaft had come apart at speed - I already had to find a replacement yoke because the old one was beat up on one of the ears pretty badly. Well, it must have also damaged the ear on the tube because on closer inspection, I noticed one of the ears had had some metal displaced inwards that was causing the snap ring slot on the u joint cup to not be fully exposed. I took a dremel tool and ground it down evenly, and the snap ring went in.