400's are usually extremely rugged, reliable transmissions- - - - -if- - - - - -and only if they're set up with the right assembly procedures and clearances, etc. They can be very unforgiving of sloppy assembly and inattention to details where clutch pack clearances and the corresponding movement of the clutch pistons is concerned. There are also a few places where a "selective thrust washer" (different thicknesses) needs to be fitted to keep the gear train from bouncing around and breaking stuff!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!