premature shifting

[betterton_ss]

Hey guys sorry if this one has been on here, used the search button but found shifting hard and late shifting.  Ok i have a 76 1/2 2wd gmc.  Has 350/th350, don't know what gears it has in it but at 60mph it runs around 2200 to 2300 rpm.  I have 275/60/15 tires on it.  My problem is i think it is shifting to early. between 1/4 and 1/2 throttle it will shif around 18 mph and between 1500 and 2000 rpm.  The carb has a dead spot which i haven't rebuilt it yet.  could it be the carb or modulator?

[bobcooter]

You can screw in on the screw inside the modulator a couple of rounds and see of that helps. Be careful not to go more than 4 rounds. Just pull the vac hose and the screw is inside the vac line connection. It's very small. You'll need a little pocket screwdriver. Just an idea.

[betterton_ss]

thanks i didn't even know you could do that

[bobcooter]

I always try the cheap, easy things first.