83 chevy swb th350 shifting early into 3rd
 

Hi all
I just replaced my carb with a rebuilt qj carb for my 305, after that the truck started shifting early into third. I have checked that the modulator has vacuum and the detent cable is set correctly (I think) not sure what could've changed to cause this issue. Any help,is appreciated

Thanks :chevy::chevy:

Re: 83 chevy swb th350 shifting early into 3rd
 

Any vacuum leaks on the carb? Was the modulator line removed or is it connected to the intake? You may have vacuum, but it sounds like something got knocked or a small hole put in the line.
What trans? I'm running on the assumption of a turbo 350.

Re: 83 chevy swb th350 shifting early into 3rd
 

Doesnt seem to have any vacuum leaks at the carb, the modulator line is connected to the vacuum tree behind the carb on the intake. This is on a th350.

Re: 83 chevy swb th350 shifting early into 3rd
 

Too little vacuum would mean the transmission would think the throttle was more open than it really was and shift late, right? Shifting early compared to before probably means the previous vacuum line was leaking. When you tightened up your vacuum connections, the shifts moved earlier.

Re: 83 chevy swb th350 shifting early into 3rd
 

so how would one fix that, adjust modulator accordingly? Sorry just new to these transmissions

Re: 83 chevy swb th350 shifting early into 3rd
 

I'd start here. Make sure it's set correctly.

Re: 83 chevy swb th350 shifting early into 3rd
 

The way that i adjusted the detent cable was to push the button in and pull back the plastic sleeve, then go into the cab and with the engine off, push the in the gas pedal all the way....sound correct? Is there supposed to be slack between the adjuster and linkage on the detent cable?

Re: 83 chevy swb th350 shifting early into 3rd
 

Sounds correct except pushing pedal in the cab. Try it again but stroke the carb wide open instead.

Re: 83 chevy swb th350 shifting early into 3rd
 

Doesn't sound right. Button has to be pushed in while the throttle is held open.

Pull the button up, then push the throttle all the way to the floor, then have someone else push the button back in while the throttle is being held open. It's a two-man job. It can be done by one person if you hold the carb open by hand and push the button back in, but I think the adjustment is more attuned to your pedal position if you do it the other way.

Re: 83 chevy swb th350 shifting early into 3rd
 

ok sent out and tried to re-adjust the detent cable, cable still has alot of slack in between the mount and the carb linkage. Is it a PITA to change the detent cable?

BTW, thanks for all the help!

Re: 83 chevy swb th350 shifting early into 3rd
 

Give us a pic of the carb with detent cable attached.
Might be something wacky with your setup.