u joint
 

On my 67 c10 i'm pretty sure the 12 bolt differential is original to the truck. The u-joints should be 1310s, I think. after installing them I realized I have about a 16 of an inch slop side to side in the pinion yoke, between the two tabs. Measuring between the two tabs I get 3.279. The 1310 measures 3.219 so that gives me the 16 of an inch. I have looked at Spicers u joint catalog and can not locate a u joint that measures 3.279. Is there a u joint that measures 3.219 and 3.279 the other? I know they make conversion u joints but those convert from one cap diameter to another. Is the 16 of an inch going to be an issue? I would think so but don't know for sure. Anyone run across this can shed some light on it for me.

Re: u joint
 

the tabs look different, almost like some has been removed from the left one

Re: u joint
 

I also think you may be looking in the wrong place. Check the flange, maybe another member has one they can measure for you?

Re: u joint
 

I believe the yoke is damaged or someone has modified it. I found I had a bad yoke on my Burban some time back. I believe it is caused by tightening the U-joint down when one or both bearing caps are no properly located in the yoke.

Photos are from my bad one.

The distance from the inside edge of each tab to the center of the pinion shaft should be exactly the same. See my crude drawing.

Re: u joint
 

i agree, the yoke on your pinion is bad, the tab on the right side in the picture is definitely shorter/smaller than the one on the left.

Re: u joint
 

Someone may have dropped a needle into the cap, making it too wide.

Could the cap shear the metal off when tightened without the bolts or something else breaking?

Could some guy chiseled the tab to make it fit?

Re: u joint
 

Straps are supposed to be a one time use. When to bolt gets tightened down they will actually stretch some to lock the u-joint cap down. when that doesn't happen the cap will spin and act like a small lathe and remove the end tab/s. If you look at the old cap it should have a polished circle where it was spinning.