Truck won't shift right

Qicchev77

LawnSite Member
Location
Montana
I have a '77 k20 with a turbo 350 tranny in it. My problem is that whenever it is in drive, 1st gear will go to about 2000 rpm then it will shift into second and about 50 rpm after that it will shift into third and lug the motor. My transmission has enough fluid. Any suggestions why this might be doing that?
 

Alan

Member
Modulator, maybe? I'm not real familiar with what it does, but I know if the vacuum line is unhooked funny things happen to the shifting. This is the small cannister looking thing on the right side of the tranny with a vacuum hose to the manifold.
 

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