I know there are threads on this subject, but I'm still not sure what to do. 5th gear quit on me driving up a hill last night. I drove another 80 miles home in 4th gear. One shop tells me that the nut backed off and they need to take the back of the tranny out, replace the nut and I'm good to go - for $900. Another shop tells me not to bother and that I should just replace the entire tran. What should I do and how much should it cost. Also, what kind of damage will I do if I drive the truck before it's fixed? Thanks for any advice.