Ok...if a automatic transmission, 1981 3AT, goes from 1st -3rd, under "normal" acceleration, is it the vacumn? If you floor it...it shifts OK thru 1,2,3. Seems to be OK when it's cold too. You can manually put it in 2nd without a problem. No other problems with the trans. 60K

 

(Paul...this is not my 78 automatic!)

My guess it that it is not related to the vacuum modulator. More likely the governor or fluid pressure/flow issues.

Governor is not cored, that i know. I'll try the filter and fluid replacement.

 

 

What "metal" governor will fit an early 3AT.

 

(Sorry, not well versed on the automatics.)

 

Todd

I think that the only steel driven gear is from the turbo, but could be wrong. If the gear is not damaged, don't worry about it.

 

But I would disassemble and properly rework the governor valving. I am beginning to think that this is where the problem starts, and that the coring is a symptom of the out of balance stuck valve.