Second gear does not have synchronizers. Therefore you have to manually synch the engine speed to the driveline speed to down shift.

Fourth to third problems probably have to do with synchronizers.

"It's just a phase. He'll grow out of it." Mama, 1964

1956 Chevy 1/2-ton 3100
1953 Chevy 6100 "The Yard dog"
1954 GMC Suburban Now with a new proud owner.