Hi My son and I just finished the auto to 4spd muncie swap on his 79 elky; on first test car on lift; all gears shifted good; went on road test and wasn't able to get it into 4th gear (grinds) came back put it back up onlift backed out hurst shift stop; tried on lift again ok; went out on road test, but still won't go in 4th? any suggestions would be appreciated. thanks John sr. & jr