3 in 400hrs is not good. Are you getting bad vibrations from the motor? Are you running a WOT? Do you balance your blades meaning, are you getting bad vibrations in general.
Ive had one re welded and its been fine since but yeah, its been an issue for many years with Hustler. Had one on an older machine crack as well but replaced under warranty.
Are you replacing the pipe or mending it? I would get it really well welded next time and see how it goes. The heat makes the steel brittle and thin but it should take 100's of hours for that to happen.
I dont know if its possible but Ive thought of a extremely high temp flexible pipe somewhere between the muffler and the engine would fix the problem. I havent looked into it though.
I would also make sure the engine is bolted down properly as well. Ive heard of issues with that too. At the end of the day its vibrations that cause the problem.
I'm not getting any abnormal vibrations that I can tell, I live on sand so my blades are replaced every year if not more as the sand just eats them away.
I welded this one back together with high hopes that it may last through next season.
I too was thinking of possibly using a flex pipe or possibly a spring loaded ball and socket style connection (like you would have on a car) between the manifold and the muffler but finding one for 1 1/2 in pipe is proving a challenge!
I checked the engine mounts and nothing seems to have shifted as far as the engine goes.
Thanks for your input and I'll keep looking for a possible solution... It just seems kinda dumb to bolt the muffler to the super structure with a solid clamp to the manifold, eventually I would think something has to give due to fatigue from vibration.
Thanks again,
Chris