Bonneville no longer shifts up...

[trucks and camper]

Hi guys, I have the following problem with my 1964 Pontiac Bonneville, We are about 60 miles down on the street, and stood at a traffic light , and were going on only in first gear .... the automatic transmission fluid is fine... I have no idea what could be the error....

please help me..

 

[melsg5]

check if the vacuum line to the transmission modulator has become disconnected

 

[trucks and camper]

...there is no modulator on it.....
the transmission is a Super Hydra-Matic "315"

 

[trucks and camper]

the tansmisson is running good, i have clean this thing...

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[melsg5]

that's the governor, figure 6-63
https://4door.com/manuals/cadillac/1963/1963_Cadillac_Manual/06 -Hydra-Matic Transmission.pdf