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Discussion Starter #1
I just recently rebuilt my 69 big block Corvette engine for the 3rd time. This time I put in a cam that produces less vacuum (I can tell by the headlight actuators), but more horsepower. I'm really happy with the engine this time, but the 400 trans feels totally different now. The shifts are real soft and it shifts from 1 to 2 and 2 to 3 too quickly. It used to wind out in first when I punched it and chrip the tires as it hit second, especially in the 2nd gear setting. Now the only way I can get it to wind up in first is to hit my kickdown switch, and even then, the shift is soft and the tires rarely chirp going into 2nd. Can the vacuum modulator be the culprit, or is it my new torque convertor, or a combination? It used to shift hard and now it doesn't even feel like the same trans. Any ideas? Thanks
 

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Discussion Starter #2
turbo 400

More info: torque converter is a 2200 stall speed (I think) and I know the rear is 3:55. Can a decrease in vacuum effect the turbo 400 so dramatically, or could it be something else?
 

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Re: turbo 400

69er said:
More info: torque converter is a 2200 stall speed (I think) and I know the rear is 3:55. Can a decrease in vacuum effect the turbo 400 so dramatically, or could it be something else?
One solution might be a shift kit? Factory transmissions are designed to shift a little slow with gear overlap so they shift smooth. A shift kit will make it shift firmer and the clutches will last longer behind the beefed up power plant.
This is presuming the trans is in good condition. If you only worked on the engine and the trans. was O.K. B 4 I'm guessing it's O.K.??? I don't remember if the modulator has an adjustment screw inside the vacuum tube?? It's been a while since I worked on 1.
 
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