Had the same problem with the tower 75 muffler.. In fact I'm on my second one now because the first one "departed" the aircraft.. After getting muffler number 2 I tried putting the whole thing together with JBWeld and found it to be no help. I think that JBWeld dries into such a hard substance that it doesn't hold up well to the vibration of a 2 stroke engine.. I Had jb weld flaking out after a few flights.. After that I was determined to stop this problem dead in its tracks.. First I took the entire thing apart and cleaned it well with mineral spirits. Then I put the whole thing back together and used the red high temp RTV Silicone for making gaskets with.. great stuff.. Then I drilled some very small holes in the muffler where the can meets the front and the back housing and put some small screws into these holes to. Lastly, I threw out the through bolt that comes with the muffler and put a piece of threaded rod from the hardware store through the whole assembly and double nutted both ends of the threaded rod.. oh yeah, also used red locktite on the two double nuts... That bad boy hasn't even considered rotating on me or vibrating loose..

http://www.rcuniverse.com/forum/m_54...tm.htm#5706658

Pics above of what I did..