When I removed the neck from my 1973 FG-160 I was curious about what the truss rod & nut actually looked like. So I removed them. I backed off the nut about halfway and used a piece of wooden dowel and a hammer to bang on the nut to start pushing the the truss rod out of the neck. Once the truss rod head was partially free on the heel end I pulled it out with difficulty. The truss rod channel had grease applied in a few places, probably to reduce the chance of rattling, but that made removal difficult since it’s had the last 44 years to dry out somewhat.
After removal I carefully measured them and made a drawing of each part. I assume at some point I will need to replace or repair one. YAMAHA FG-160 TRUSS ROD PDF
I assume the truss rods are the same length in all Vintage FG’s that have the adjustment in the headstock. I will remove others and verify when doing neck resets and list models checked here.