Ticking overdrive?

[Darrman]

I am having a weird problem, my truck has the mazda 5speed 4x4 trans, rebuilt unit installed about 2 years ago, and about 8k miles on it. I recently took a 600 mile trip to the coast in it and when I came back about a week later the trans was ticking in 5th gear. NOTE, it only ticks in 5th and has a slow rate of ticking, about the same speed as the second hand on a watch. It DOES NOT speed up or slow down with acceleration, which is weird.
I have installed a Hurst shifter, which as some may know makes things noisy, but this is something new.
I may have screwed it up worse tonite driving home, as the truck started shimmying and them all of a sudden the ticking got much louder. I dropped it back to 4rth and kept going as I dont want to be stuck on the side of the highway at 1 in the morning, lol.
I will look at it tomorrow, but for now can anybody help me out with ideas what could be causing this, it may not be the trans at all, but something else in the drivetrain, like the transfer case.
Thanks!

 

[JohnJ]

Just when you think it can't possibly be a bad u-joint....

 

[Darrman]

Unfortunatly, no, I checked everything today. I replaced the ujoints awhile back, but would have been happy to have one go out rather than a new transmission, but thats what it looks like. I am going to try taking out the shifter this weekend and have a look inside. I can feel the ticking in the shifter.
Also yes, I did screw it up worse, I tried 5th today and what a horrible clacking noise and the truck was shaking, not bad but you can feel it. Yet as before all other gears work perfect.