Thoughts On No Kickdown THM-350
 

As the title indicates, THM-350 that won’t kickdown has me stumped. It up shifts and downshifts as normal. I’ve changed the kickdown cable and adjusted properly. Even tried every other adjustment (too loose & too tight) and nothing changes. I recall in my dealership days that if the governor gear was sheared, the trans wouldn’t shift out of 1st gear. If the governor valve was sticking it would hold shifts too long. Likewise a bad modulator would alter shift points making the issue noticeable right away. The detent linkage rod seemed to be very easy to pull up out of the case but seemed to spring back. Wondering if the kickdown valve in the valve body could be sticking?? Any thoughts are appreciated.

Any idea of any modifications? Its possible a shift kit disabled the detent valve. You don't absolutely need it if you have a good ratchet shifter, and/or you're racing it and dont want it to affect shift behavior.

It should delay upshifts and force downshifts when pulled. Its also possible the governor thinks the road speed is too high to downshift, but you would typically see it shifting too early under normal operation. If you're happy with the part throttle shift points and shift feel, check the governor and VB for a shift kit, but make small changes so you don't upset the apple cart.

Thanks for the reply. The trans shifts normally (stock) and does nothing else to indicate that the valve body, governor, or modulator has been altered. Yes I can manually shift-downshift when needed. It would be convenient to have the transmission shift into a lower gear when needed since this Firebird has a 2.56 rear. I’ll live with it for now.