ANY ADVISE AS OF WHAT TO LOOK FOR WOULD BE APPRECIATED!! I HAVE A 72 CHEVY K20 4X4 W/ 18" SUSP, 44'S, NP205 T-CASE FRESHLY REBUILT, NEW 5.13 GEARS, 454 ENG, AUTO 400 TURBO TRANNY FRESHLY REBUILT, AND THE TRANSMISSION HAS BROKE 3 STOCK INPUT SHAFTS CLEAN IN TWO W/ NORMAL DRIVING!! MY TRANS GUY FINNALLY PUT A HEAVY DUTY, HARDEND INPUT SHAFT FROM TCI RACING W/ DRUM AND NEW PUMP THIS TIME, BUT HAS NO CLUE WHY IT KEEPS BREAKING...? TRANS GUY THINKS IT MAY BE SOMETING TO THE EFFECT AS A BAD ENGINE/VIBRATION ETC, MY MECHANIC THINKS IT'S THE TORQUE FROM THE BIG TIRES/LOW GEARS/BIG ENG COMBINATION AND A STOCK INPUT SHAFT JUST CANT TAKE IT. HE SEEMS TO THINK THE HEAVY DUTY SHAFT WE PUT IN THIS TIME WILL FIX THE PROBLEM....? ALTHOUGH THE PAST 2 TIMES THE TRANS GUY COVERED THE COST OF A STOCK REPLACEMENT WHEN IT BROKE, THIS TIME IT COST ME $700 TO HAVE HIM PUT ALL THE GOOD PARTS IN IT TO FIX IT AGAIN AND I'M AFFRAID TO DRIVE IT. ANY IDEAS OR COMMENTS WOULD HELP, IF NOT TO SOLVE IT, JUST TO EASE MY MIND. I CAN'T AFFORD $700 TOO MANY MORE BREAKS, BUT SO FAR IT'S HELD UP. BUT I'VE DRIVEN IT VERY LITTLE!! ANY IDEAS FROM FELLOW 4X4ERS AS TO WHAT WOULD CAUSE THIS OR DO YOU THINK IT JUST NEEDED A HEAVY DUTY PART?
You should be fine now since you have the hardened input shaft and drum assy. I agreee that the gears, large tires and engine power are what were breaking your stock components. We build Th400s for mant different monster trucks with the hardened shaft and drums in them and don't see a break very often. And you know what kind of gearing and power they have--so don't be afraid to go thrash you rig and see what it will take now. So far your cost seems good--one super drum for a TH400 costs around $700.
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ANY ADVISE AS OF WHAT TO LOOK FOR WOULD BE APPRECIATED!! I HAVE A 72 CHEVY K20 4X4 W/ 18" SUSP, 44'S, NP205 T-CASE FRESHLY REBUILT, NEW 5.13 GEARS, 454 ENG, AUTO 400 TURBO TRANNY FRESHLY REBUILT, AND THE TRANSMISSION HAS BROKE 3 STOCK INPUT SHAFTS CLEAN IN TWO W/ NORMAL DRIVING!! 
