craftsman lt4000

hi i have a craftsman lt4000 model # 917257640. i locked the transaxle in it and it worked great untill my terrible weld broke. i then re locked it with a much beefier weld and removed all the metal pieces from the preveious one breaking. then the other day i was romping and only one tire was spinning so i thought i broke it AGAIN. i took it all apart and it turns out the drive pin i welded the gears to broke right in half! it seemed like it twisted off. and there was a tooth missing from the gear on the end of the axle. i found the tooth in the transmission (luckily did not get caught up in anything) and welded the pin back together and buttoned everything up. now, when i drive it every once in a while theres a terrible bucking and almost hammer-hitting metal sound in the transmission then it smooths out and drives fine. i would like to get a new drive pin and gears but cant find any site for the parts. or upgrade to a beefier transmission such as a peerless mst-206. but will the peerlesss fit on my tractor? and the only one i can find for a decent price has a broken mounting bolt hole. so any idea where i can get one? thanks guys

What type transaxle are you running now? A MST transaxle should fit in, if not it isnt hard to get them to.

im running a spicer transaxle model number- 4656886