[saxit2me2]

Here is a problem that has me worried (of course)
I have a 67 GP and it came with the 3 speed auto trans. If i'm driving normal(not tearing through the streets) the tranny shifts well and no issues as far as I can see. But if I get on the gas from a stop light the car accellerates and will shift from 1st to second but never to 3rd until I let off the gas. then it goes to third and smooth sailing. the other thing it does is if I'm going about 70 and I floor it, the tranny can't decide what gear to be in. the RPM's go up and down sporadically like it goes from 3rd to Super gear and back up to 3rd. I have a rebuilt engine with a cam taller than stock it is the 262h extreme energy from comp cams. so any ideas? maybe a vaccum problem to the modulator? Thanks.

[saxit2me2]

Here is a problem that has me worried (of course)
I have a 67 GP and it came with the 3 speed auto trans. If i'm driving normal(not tearing through the streets) the tranny shifts well and no issues as far as I can see. But if I get on the gas from a stop light the car accellerates and will shift from 1st to second but never to 3rd until I let off the gas. then it goes to third and smooth sailing. the other thing it does is if I'm going about 70 and I floor it, the tranny can't decide what gear to be in. the RPM's go up and down sporadically like it goes from 3rd to Super gear and back up to 3rd. I have a rebuilt engine with a cam taller than stock it is the 262h extreme energy from comp cams. so any ideas? maybe a vaccum problem to the modulator? Thanks.

[stevep]

Dan,tee in a vacuum gauge at the modulator and drive the car.You should have at least 15" of vacuum at an idle and it should drop to about 8" at full throttle.You should be at 15-20" at cruising speed.If your vacuum is erratic,there's your problem.You could have a plugged,restricted,or broken vacuum line.

Also take the line off the modulator and if ATF drips out.You need to replace the modulator.

If all is OK,take the modulator off and see if the valve behind it moves freely in the bore.

[Half-Inch Stud]

Suggest you adjust your Vac Modulator to accept the new cam's vacuum-signal personality.

Otherwise, replace the Govenor with a NUMERICALLY higher inkstamp. Your present govenor is likely stamped 11 or 13. Find and install a 21 or 23 or 25 or 27 if you find any of those.

...Passing gear will feel a world more exciting.

Have a nice cruise.

H.I. Stud

[a69gto4me]

I would also say the problem is in the modulator valve area. Make sure you have no leaks between intake and valve. If the vaccuum checks out to be steady but low you can experiment with different valves or you can buy a B&M adjustable modulator valve. Trans-dapt, Dayton and a few others also make the adjustable valve.

[goathead68]

I'd check the governor. I got a core trans, had that rebuilt and put it in my car. Upon installation, it had the same shifting problem you have. I pulled the governor and found that one of the weights was screwed up. I can't remember if the pin was bent or what, but I did take the governor out of my old trans, put that in that in the new trans and the problem was solved.

Just my two cents.

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