It sounds like it’s not fully seated. Disassemble and hit the male insert with some white lithium grease. Drive it in with a rubber mallet. Unless you turn bright green when you get angry, you won’t hurt the exhaust. Once you think you have it fully seated, continue to fully seat using the mallet. When you get tired, switch hands. (with the mallet, get your mind out of the gutter).
Grab a pint.
Get back under the truck and continue because you might think you’re done, but you’re not. Now, you’ve been beating on it for 20 minutes with the mallet and it’s not budging. retried a 3 pounder from the garage. Use a 2x4 or similar to absorb some of the impact. Bonus points if you employ a no bounce 3#’er ;-).
Continue inserting the uncooperative exhaust until all movement stops. continue the pounding for 20 more minutes.
grab another pint.
clamp the exhaust now.
retest.
