Super MTA Low Range

The T/A is stuck in low range. I tried adjusting the linkage last year or the year before, and think I followed the manual, but still no high range so I didn't road it home. The linkage looked OK to me, and is in much better shape than my 450D which works fine.

Where should I start after double-checking the linkage? It was overhauled by someone who did a nice job on most of the tractor, but he could never get it into high range after rebuilding it either. He says he removed the T/A and had it rebuilt. He's now moved away and I can't contact him. I bought the tractor from him as part of his pending divorce which is now complete. Since he was eager to sell the tractor, he may have not told me the complete truth but did point out the T/A would not shift. As usual I bought it without driving it, but at least I saw this one first.

I really can't remember if it will free wheel, I only drove it two miles before storing it.

I farm with M's and I do know it is in low range.

If it was welded or had an eliminator, would it not be high range only?

Being an optimist I'm hoping it was put together wrong, like the fork for the throwout bearing not being in the groove so the clutch is stuck disengaged. I've never had a T/A tractor apart but it looks like it is time to learn.