I have an 11.5' camper on the back of '05 sw F350 PSD and use the Super Hitch truss system for pulling a 12k trailer with the zuk and gear. The extension is 48" tip to tip. I'm also using airbags. When I bought the camper, I knew I needed an extension and did not feel comfortable building one...
My brother used to drag race a 12sec Volkswagen Rabbit. He had problems breaking the stub shaft on the front axles. He finally sent a set out for cryo, sorry don't know where, no more problems. That set of axles were still in the car when he sold it.
RADesigns.
Installed in my zuk. Haven't actually used it yet but it was the only way to fit an auto shifter. RADesigns makes those too, but I made my own.
I think poly or nylatron would give up after a while, especially if it is being worked hard. Brass will outlast plastic.
I think what really fixed my problem was the new retaining cup. The old one with bent ears would allow the shifter to lift and disengage the shifter forks. I had another...
I had similar problem with tcase. Got going again by pulling shifter out and used a screwdriver to put it back in gear.
I installed a new shifter bolt and solid brass shifter sheet from Zuks Offroad
http://www.zuksoffroad.com/Garter-solid-brass-t-case-shifter-sheet_p_89.html
The groove in...