I bought the truck with around 117k miles on it. Owned for almost 6 years and now has 145k miles. I replaced the stock tranny at about 130k miles with a brand new tranny that is under warranty. Shortly after being replaced (2 weeks) it failed again and replaced under warranty. Now about 15K miles later I'm having issues again l. As of today, on my way to work it was having difficulties shifting from 5th to 6th. I came to a stop at a light and then it wouldn't shift from 3rd to 4th. Had it towed back to the shop and waiting to hear back. Reason im posting This is because I'm curious if there is any possibility if something in my truck is causing A transmission failure or if its the part store that is selling my mechanic bad transmissions?