Tranny problem could be a badly tuned chip. Whos chip is it?? If the tranny is still stock and if the truck has towed much aything pask 100K is borrowed time (and you are very close) IMO. This engine is very durable it is wayyyyy underpowered as caryt said 400+ hp is very safe if done right but your tranny will last about a day at that hp level. A 36' toyhauler and you better just drop the cash and get a BTS tranny cause stock it ain't gonna last long for sure you are going to spend 5k anyway when your tranny goes south...JMHO...