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vacuum leak or fuel pump Randy
check vacuum pump.
No because this will not be the proper signal from manifold vacuum that tells the transmission what kind of throttle position and load the engine is under.
No
hand operated vacuum pump . hook up and and apply vacuum and open bleeder and keep applying vacuum then close bleeder. repeat x4
Of course, there is no other way to get at the pump.
remove the transmission and torque converter. Remove the bolts from the pump (front of transmission case) and remove the pump.
The automatic hubs are activated by vacuum. Check for broken or disconnected vacuum lines especially behind each front wheel.
Remove the hoses from your 1978 Chevrolet 350 cubic inch engine fuel pump. Remove the fuel pump belt. Remove the fuel pump retaining bolts. Reverse the process to install the new fuel pump.
The vacuum modulator is located on the passenger side of the transmission, just above the tranny oil pan. It has a vacuum line going to it. It actuates a valve in the tranny for upshifts.
Check the fuses.
As long as you have the electric pump in the gas tank your fine.