2003 explorer 4.6 exhaust leak

won't affect the u joint at all. I'd be more concerned about exhaust fumes back into the passenger compartment. And I'd take 15 minutes and have someone tack weld it with a wire feed just to hold you over, throw someone a $20...

I used a very sticky tar base exhaust tape on a completely broken tailpipe assembly before the muffler of a small motorcycle due to the noise. It worked so well I completely forgot about the break because of the lack of noise for several months.