John like bighammer said pump up your U joint untill you hear or see water coming out (not a good sign) or air but dont get carried away there should not be gobs of grease coming out. Intervals very with type of grease ( here we go again ) and usage loaded/empty. We used to use Red Ram but that is discontinued in Canada but may be available through Red Tek?, we tried some other stuff but it disappeared real quick. Now using that rotten A----- synthetic and in the big truck which is greased weekly it will take no more than 1-2 pumps max in each joint. Red Ram was 2-4 pumps and the pretty green Esso 5-8 pumps, the Red Ram would never expell any water nor does the synthetic and took out first U joint at 986,000 kilometers= 580,000 miles. The slip joints are different, pump until you see grease at either the yoke end or the spline end, CV joint thats another story most come without zirks. When shaft needs to be refitted I put zirked U joints in and squirt high pressure synthetic into that goofy ball arrangement, same for steering knuckle joints, they are available. Dealer will try to sell you original part # tell them thank you no Hayes Dana makes them all with the zirks. Hope you gained something out of all this, my wife thinks I have a love afair with all this junk. She sayes I'm in it, on it or under it more than her or the house. PK