Road ranger 8 speed adjustable clutch?

F700 with the nutless 429?

 

Ok RT6609A: R stands for road ranger. T is twin counter shaft. 6 says it is rated for 600 foot pounds of toque. 6 tells you the gears are straight cut? 9 tells you it is a 9 speed but the one behind reverse is Lo. That is not counted so it is an 8 speed.
I am not highly familiar with the 6 series but it likely works like the 9 plus series. The back box can be changed and make it a 13 over or a 8 speed double low, 8LL. When someone makes one of those the tag lies.
That little switch on the shifter that looks like the knob is broken off of reminds me of an old school deep reduction shift valve. A transmission like that could be or have been there.
About your clutch: Sounds like you have no other adjustments but the linkage If you have 1 inch of free travel no adjustment will make it better. Sounds like the clutch disc or disc's have resistance to slid on the input shaft.

 

He said they don't count the LO gear, which is below the reverse gear in the shift pattern.

Which is kind of odd to me because they count LO as a gear in an 18 speed.

 

And 13,9.

 

It looks new. I would maybe try cleaning up between the input shaft and disc with brake cleaner then apply some kind of slicky stuff.
Sounds like the disc may not be free to slide on the shaft.
Had a Dodge like that once. Replaced the clutch in a hurry. Did not check the disc on the shaft before installation. Had to put it in gear before the engine was started. It got better.

 

There’s 2 guys on here that probably would like to have that tranny @alfio @Hopeaholic if you want it gone. I believe what you have is a push style clutch with an air operated countershaft brake and that’s what the broken knob on the side of the shifter is for.

 

this it trace down that air line I bet it goes there

 

Must admit. Never seen one. Never worked on one. Didn't know those existed. Before 10am on a Sunday and I've learned something new. Gonna be a good day.