I had a similar issue with my Axis 500. After replacing the shifting fan gears which suffered from the common corrosion issue that ate up the gears, I still could not adjust the shift linkage to cover all the gears reliably. If I adjusted the linkage to reliably shift into reverse, I could not get into first either reliably or at all. If I adjusted the linkage to go into first, I lost Reverse. I also noted that when I went from Reverse to Neutral, the dash indicator would not show the "N" unless I moved the shifter towards Hi and then came back to neutral. That kind of indicator issue was common no matter how I adjusted things. I also noted that the bolt that holds the shifter linkage onto the engine end of the shifter shaft kept coming loose. I disassembled the fan gear cover and even realigned the fan gears but still had the same issues. I decided to take a closer look at how the shifter was working. When I watched the location where the linkage connected to the fan gear shaft, I saw what is in the photo. The metal on the linkage arm had egg-shaped the mating slot so there was a large amount of backlash in the shifter movement before the fan gear shaft started changing gears.
Being cheap, I decided to use JB Weld to run a small bead arouhd the linkage arm hole and slide it gently onto the shaft being careful to not get any epoxy into the bolt hole. When I then slid the bolt into the hole with the required lock washer and flat washer, the flat washer squeezed the epoxy along the face; effectively gluing the flat washer to the shifter arm. This means I can still remove the washer if I have to, but the flat washer will not allow the shifter arm to rotate as I shift. The epoxy fills the excess space between the shaft and arm, so there is no longer any backlash on the arm and the bolt no longer looses over a few shifts. The result is a fully adjustable linkage with no excess backlash. It now shifts reliably into all gears and the indicator link matches the transmission position.
A much more expensive solution is to buy an entire new gearshift assembly from the shifter to the end of the linkage arm. Several sources such as Hisun, Ebay, Amazon, etc sell this assembly kit for prices starting at around $50. There is a source that will sell the transmission end of the turnbuckle unit alone, but that will set you back about $25 plus shipping.
I hope this info is useful and saves you lots of time and money.
