sentences:  The prototype did not have a muffler or pipe rather the exhaust was routed through the frame.This proved to be an inferior design because the condensation and acidic fumes caused premature frame failure.A competing prototype by Willys, the 1953 Bobcat or "Aero Jeep", which would share as many parts as possible with the M38 and M38A1 to save costs, was rejected in favor of the more advanced M422.