Jianis, I'm not aware of any factory vacuum gear change assist. It may be after market. Post this question in engine and driveline with more details on it and maybe someone will have heard of one.

"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.