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1980 Pontiac Firebird not shifing out of second

I have a 1980 Firebird. I replaced the plugs, wires, Distributor cap and rotor. It was shifting fine before I replaced these now it will not shift out of second. Is it possible I did something or just a coincidence?

Replacing secondary ignition components shouldn’t have any effect on the transmission operation.

Have you checked the level/color/odor of the transmission fluid?

Tester

Yep first thing I did. I checked it level and idling and it shows just a quarter inch below full. Not to the add a pint yet. color is red not brown.

My 80 Grand Prix w/301 had a birds nest of tubes/wires/ducts on top of motor. I wonder what you left unplugged?

Just a guess, line to transmission vacuum modulator off.

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Something like that seems a likely guess. On some automatics of that era — don’t know if this applies to a Firebird — there’s an throttle position input to the transmission that uses a cable. If applicable make sure that cable is doing its job. The other common input to an transmission are the vehicle speed and the intake manifold vacuum vacuum. If the transmission is getting all its inputs and refusing to shift from 2nd to 3rd, got to think there’s a problem with the transmission at that point, coincidence, unrelated to the recent work done. Dropping & cleaning the pan, replacing the filter, and filling w/fresh fluid would be where I’d start.

I will look for a vacuum line off in the AM sounds like it could be it.

From what I’m seeing for the 1982 Firebird at least, no info here for 1980 version, but on the 1982 the automatic trans doesn’t use a vacuum modulator. Uses the throttle cable input method.

https://www.rockauto.com/en/moreinfo.php?pk=45218&cc=1250648&jsn=442

Tester

Or a leak.in the vacuum line to the modulator

Thanks all, it was a vacuum line I bumped off.

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Hey buddy, how do I get this car, out of second gear? ( Beep beep, beep beep, his horn went beep, beep, beep)

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Tester

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had a modulator rupture and started sucking trans fluid into intake.