My 71 Cutlass, shifts late going from 2nd to 3rd (about 45 mph). From 1st to 2nd, seems fine. How can I determine the cause of the late shift. Any advice would be appreciated.

 

First thing to check is the easiest: How's your vacuum modulator?

- Eric

 

What is the best way to test the modulator to determine if it's good or bad ?

 

Ed,

1. Pull vacuum hose from engine connection.
   Presence of ATF means modulator is bad.
2. If no ATF, attach vacuum hose to line (long enough so you're not hanging half inside the engine compartment), suck on hose until there's too much vacuum to suck any more out.
   If there's no endpoint, modulator's bad.
   If vacuum leaks down, modulator's bad.
3. Finally, if all else fails, remove modulator, attach vacuum hose, and suck - plunger should pull in and stay in when you hold your finger over the end of the hose.

- Eric

 

Check your governor.

The governor is basically a road speed sensor. The faster you move, the more pressure the governor allows through until it overcomes the shift valves and your transmission up-shifts. If the passage is clogged or the weights are sticking you may get enough pressure for 1-2 shift, but not 2-3.

On a TH-350 there is a dome cover right before the tail housing on the left side. This is the governor housing.