Tranny linkage adjustment

What shifter do you have? If you have a Hurst comp-plus with the stop bolts, these need to be adjusted in 3rd and 4th (NOT 1st and 2nd).

But like mentioned, you need to pin the shifter, get all of the levers on the trans in neutral then adjust the swivels.

Also check the condition of everything, if the swivels, holes in the trans levers or holes for the swivels on the shifter have worn, that can cause problems.

Take some pics.

Are you sure it isn't your clutch adjustment?

Do you have oil in the transmission?