What makes a TH350 weaker than the TH400? from what I have observed on this forum over the years is that the sprags in the TH350 bust after a few good hooks. is it just that people don't give a TH350 the chance and it is assumed by the majority that it is weaker b/c Chevy put TH400s behind big blocks or what? I hope this makes sense to somebody :confused: .

It is weaker but stronger than given credit for. For most 11 second cars, it is plenty strong. It weights less and takes less power to operate. Mine has been working flawlessly for 5 years in my 11 second car.

I ran a th350 and a B&M 11"converter behind my 454 for 4.5 years with out a problem,ran a best of 11.78. I made the switch to ATI 10" converter and a th400 and it lasted maybe 90 passes before the clutches were toast and never picked up any e.t., I'm hoping there was some undetected slipping going on and we might pick up a little now,mainly due to the converter. They say it takes a little more HP to run a th400.

I run a Th350 in my 67 Chevelle running a best of 7.39 in the 1/8th with a 1.59 60'. The trans has been in the car for 5 years now, seeing mid 7 sec. passes for the past 3 years. I have heard that 550-600 hp is about the cut off point for a dependable 350, however I know some guys have pushed them well into the 10 sec 1/4 mile range and made them live. An HD intermediate sprag is a must, and other things can be done to help the clutches live. You can also buy or have the direct clutch drum machined to hold 5 clutches, which helps under high hp applications.

my 350 takes a beating week in and week out see sig.