Seeking gearbox expert advise, lost 5th & 6th gears

[Smallblock454]

Hello Giller,

thanks for the photo.

Problem i see is that you have to manage to bring everything together exactly and without tenseness. Means to fit the shafts into the bearings of the housing and torque the housing to the differential. In general this is why you mount the gearbox housing to the differential while the differential shows shafts up.

5th and 6th gear: Don't think it can be caused by the cable. If one gear works and it is the right cable, shifter and gear lever all gears should work. More probable that a claw can cause this problem.

Have you tested to put in 5th and 6th gear manually at the transmission?
Do you have a short shifter mechanism?

Regards, Markus