Th350 transmission no 3rd gear

I have in 1984, Chevy G 20 With a 305 and turbo 350. The vehicle runs and drives flawlessly. However I changed the spark plugs and some dome lighting, and I heard a wire short out which blew two fuses both Which controlled dash lights and tail lights. I replaced both fuses five minutes later went for a drive again and I don’t have third gear. What did I do. No it’s not a governor or the linkage or the vacuum on the module

Have you’ve ever had the transmission fluid/filter serviced?


I am not a mechanic so bear with me. My wild guess is that it’s barely possible that you screwed up the torque converter lockup solenoid but AFAIK that year those transmissions still had hydraulic controls vs. electronic. And as Tester says, it could also simply be coincidence.

I think you need to go to a trans shop. I had a mechanic blow out the solenoid for my 4th gear. I told him not to but he put a full 12 volts on it testing it and that was enough. So I think some actuator got fried in the process.

Inspect the throttle valve cable connection at the carburetor and transmission.

Thanks guys, I just changed the fluid on the off chance that may have been the problem. No change :/. I was thinking maybe solenoid as well. I may bring it in today

Sorry for my ignorance, what should I be looking for?

1 Like

The TV cable should move in unison with the throttle cable. It should be taught at wide open throttle and pretty much no slack but not “tight” when the throttle is closed. If you’ve knocked it out of adjustment, it’ll change the shift points. It’ll stack shifts if it’s too loose, or delay shifts if it’s too tight. Not sure how it would make you lose third. Maybe if it was extremely tight…?

I think you might be on to something there, maybe.

Check the fuses in the fuse panel. Should be one in there for trans if it has any electronic controls, I’d think.

I really appreciate your Help guys I was doing a tuneup because we’re going on a family vacation in just a few days supposed to be taking the van.

And what’s interesting is I see that cable coming off of the transmission going up to the engine compartment but there is only one throttle cable on the carburetor and that connects to the gas pedal below it there’s no other cable


Sorry for the confusion - I have a turbo 400 transmission

OP can change thread title.

TheTH400 relies on a vacuum signal for upshift timing. Measure the vacuum at the modulator with a vacuum gauge and check for transmission fluid leaking from the modulator vacuum nipple.

There is a small amount of trans fluid coming from the mod when I removed the hose, pressure is high and can feel a hard suction, 16. Literally under here now

For a long time the hose connected to the mod was rotted a but the transmission still shifted just a high rpm and very hard. I connected hose and ran like a gem. Until the other day when above problem started. Could an electric kick down selenoid cause this issue?

What was the color was the transmission fluid when you drained it?


It looked really good it was pretty much bright red like the second one down.

Did you replace the vacuum module?