67 C-4 not going into 3rd

Just rebuilt, doesn’t seem to want to go into drive,3rd. Could the kickdown adjustment be causing it?

Any ideas appreciated

Thanks

Could be but the typical cause is the fluid level is too low.

Can you manually go through the gears ? May be vacuum modulater

Tim remove the vacuum line at the modulator on the right rear of the transmission and verify that you have manifold vacuum when the engine is running. A lack of adequate vacuum to the modulator will prevent a shift into high gear.

I will check that.

Thank you KL

The vacuum modulator itself could be defective.