5 ton Sprag Switch

I never thought about locking hubs but I don't drive any 809 series more than 200 miles from home. In my case I will pay for the extra fuel and leave my set up stock. Bet if you can find them with the cost you could buy another truck. Yes you would need to do the air cutoff if you had locking hubs/ desplined hubs to drive it.

Are you sure Wes that there is a neutral position? When I had my 809 sprag out, there seemed to be only 2 positions (reverse and forward). I was going to document the entire removal and assembly but there didn't seem to be an interest at the time, so I didn't.

I remember one air line which acts against a spring for reverse. Your last picture shows one air line into the cylinder...is there a second to throw it the other direction, I don't remember one?

Keep in mind that the front and the rear (in the TC) have different gearing where the rear is always trying to overrun the front and the sprag relieves the difference in speeds between the shafts. Sprag is not intended to be used as a neutral and turn full axle rpm between the two parts. I don't remember lube that would handle that The difference in gear is something like 15/1 and 16/1 (not sure exact numbers any longer).

I can see why towing is a problem, since one side of the sprag is turning full axle rpm and the other side not turning at all...thus going 15 or 16 times it's normal speed.

Yes two lines coming off the poppets going to the air cylinder. The cylinder piston has two springs on both ends. Without full air pressure the spring can not be completely compressed to engage the sprag. This is what they are calling neutral.
Here is the pic of the piston with one side spring installed and retainer clip holding the cap and spring in the piston. The other pic is not put together. When the cylinder gets enough pressure the spring does it's spring thing and the sprag shaft will move about 1/2 more to engage the sprag. As said without air the spring keeps the piston from moving the shaft far enough to in gage the sprag.
The pic with the cap seated into the piston is what it would look like if there was enough pressure to compress the spring and in gaged the sprag. I just left out the spring.

Going through my photos from my tear down on my M813. Switch goes in the line on the bottom (closest to the ground) correct?

No. Supply line to poppet. While your there tighten all eight of the retaining 7/16 bolts that hold the poppet together / to the transmission.