Here is a picture of my 2006 front driveshaft. The zerk is not on the U-Joints, but on the part inbetween them. You will have best access to it if you have your head under the transmission and move your truck forward until you see this. Here is what you are looking for:

 

Nice pic, its very hard to find the fitting without the pic. I had a hard time until i saw a pic over on TDR.......this pic is very good, if you cant find it after that pic?

 

I looked for mine 3 times this past year and gave up. Even with the good pics!

Just found it last week.

I do this work every day and I still had a difficult time.

 

How much play is normal in this cardin joint?