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ironmike, ASE Master tech
Category: Chevy
Satisfied Customers: 3377
Experience:  30 years ASE Master L1 GM certified
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1979 Chevy: 400 turbo, 4 wheel drive, automatic transmission..flywheel

Resolved Question:

1979 Chevy pick up, 400 turbo,XXXXX automatic to manually place into each gear, but will not change out of low gear automatically. Stays in low gear. Recently removed motor to replace flywheel.
Submitted: 6 years ago.
Category: Chevy
Expert:  ironmike replied 6 years ago.


did you try applying vacuum to the modulator with a hand tester while driving?

Customer: replied 6 years ago.
No, I do not have a hand tester. I did change the vacuum hose though.
Expert:  ironmike replied 6 years ago.
I would try that or put a vacuum gauge at the same port the hose comes from and watch as you drive. you should see around 18 (15 minimum)at idle and vacuum drop as engine rpm increases.
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