Hard shift from 1-2 and doesnt shift into 3rd til almost 50mph

[Steve W]

The car has been running great til just the other night. All of a sudden, just cruising down the street...its a very hard shift from 1-2  and doesnt shift into 3rd til almost 50mph.
Tried getting on the freeway and accelerating on the ramp...same thing. The car holds first gear longer and then "whooomp"...a hard, lurching shift into second gear. Then at around 50 a smooth shift into 3rd.

No harsh down-shifting though....yet(?)

What could be causing this?

1968 Cadillac Coupe deVille 472 with th400 Trans. (All original, all stock, 190k miles)

[Scot Minesinger]

Look at the vacuum modulator and vacuum lines from carb to metal tube, and metal tube to modulator at trans.  The vacuum modulator is $15 at NAPA and the vacuum hoses are pennies, so if there is a question as to the health of these parts replace them.  Remember vacuum hoses can look good, but not be.  You can also consider changing fluid at this time too, or draw it out thru dipstick tube to make the vacuum modulator change out.

[Gene Beaird]

1. Verify the fluid level is full
2. Make sure the vacuum hose to the transmission vacuum modulator hasn't come loose, or is cracked.  There will be a short vacuum hose at each end of the vacuum line going to the vacuum modulator on the transmission.  While you're under the car, pull the vacuum hose loose at the modulator and make sure it's not wet with transmission fluid. 
3. If you find no problems with the above, you may want to replace the vacuum modulator.  Be careful replacing the retainer clip bolt, it's going into aluminum.  You want it snug, but it's easy to strip if you get too carried away.
4. If that doesn't fix things, you may want to look at the governor drive gear and make sure it's not stripped out. 
5. Anything more than that, and you may be looking at something internal.