Transmission question

I have a 1921 running chassis and I can’t get a neutral. I’ve done all the obvious, at least to me, checks. There is 3/8" movement forward and aft from the driven gear to the driving plate when forward pedal is pushed. Unknown history on the power plant, but it looks clean. Possible assembled wrong? Can I pull the unit from the top without removing the engine.
I’m looking for advice and suggestions on how to proceed.
r/s Bob

I wish I had an easy answer, but I have been buffaloed by this before. I suggest you start here:

the problem, from my experience, is that it is all interconnected and interrelated, where to start? Set everything to factory as in the article, then try to hone in on the problem. I do not believe you will find a quick solution…