I swapped the synchros (all 4) out of an M45 I have (don't ask me to explain why).

Previously, the car would have trouble downshifting from 2nd to 1st and popped out of 3rd on deceleration.

No broken teeth or other terrible wear found inside. I pulled the box apart per the Bentley instructions. No big woop, replaced all the synchros, used exactly the same shims, new gaskets all around.

Before I put it in the car, I thought I'd check the shift gate on it. It clicks into R, 1, and 2 no problem. Does not want to go into 3 or 4. When I had the top cover off and that top 2-piece (let's call it a gate), I noticed that the rear (3/4) selector fork was not always lining up with the slot in the gate mechanism.

So is this possibly an intermediate shaft issue? Was something not shimmed right? I didn't end up with any spare parts! I have two other donor boxes that I could get into (each with various problems). Suggestions on where I should start troubleshooting? Nothing is binding up when in Neutral or the gears that seem to work (input shaft is fine, output shaft turns). Thanks.

...Brian....