My truck just went back to the dealer for the ongoing grind in 4th and sometimes 3rd. This was my third complaint since I bought the truck. The service manager called me later and said they were replacing the whole transmission because 6 speeds shouldn't grind like this! Wow! They replaced the transmission and it shifts like glass now. I can't believe I settled for that crappy grind for so long and just assumed that it's normal. My old transmission would quit grinding after it warmed up (usually). The new one shifts just as good cold as it does hot. The dealer also said my old transmission was full of metal shavings. I hope this story motivates others with the intermittent grind to have it checked out!!!
Karl
Karl