... I could grab the input shaft and turn it a few degrees (maybe 10) by hand without any resistance. Is this normal?
I'll quote myself here... I can assure you that tire sidewall flex was not what allowed me to turn the steering box input shaft by hand.
For what it is worth, the only time this thing is driven on the road is to and from the garage or to and from the trailer to the trail. In most cases < 10 miles one way on isolated roads. This is a new problem that came up within the last 6 rides (unfortunately, this goes back to last October.)
This makes me uncomfortable and so I don't drive it.
I found an article on the net that discussed the Saginaw box. I interpreted the article as saying that a movement of just under 1" at the steering wheel is normal for the saginaw box. This is about what I have at the wheel.
After test driving it again, to better feel the problem, I am still leaning toward a tire balance problem coupled with the low air pressure run offroad. I have added BBs to balance the tire. That helped as I was able to drive upwards of 45 without the deathwobble. But it is still not comfortable -- nor do I feel safe with the current arrangement.
Prior to this happening the first time, 8 months ago, I had the exact same setup -- axles, tires, wheels, for 1.5 years. I could run at 70 mph with 8 psi without bouncing. I just could not turn. Heck, Jeff and Joel followed me down the interstate in Indiana two bashes ago without any issues...
I suppose that the real test would be to take the BBs out and rebalance the tires on a machine to see if this goes away.
Thanks for all of the help.