Sticking in 5th gear
There is another reason that the trans will stick, and it is not good. I had one fail because I lost teeth from fifth gear and the counter gear which got stuck in such a way you could not shift out of fifth, or maybe the broken teeth bound up, not sure on the order. Will make a really bad clicking noise in all gears if this happens.
This happened on a Standard Trans full spline rebuild at 13K miles with a total towing distance of 300 miles (5K under GCVW). They wouldn't work with me at all, even though I only had the trans in the truck for 10 months. Used the spec Castrol oil too!
I am really thinking about other transmission options.