Olds 455 / TH400 all stock. Car was in storage all winter. Drove it around the block the other day for the first time this spring and noticed it was not shifting into 3rd gear. Transmission fluid level and color is good. It shifts fine into reverse. It shifts fine into 2nd. For some reason, it does not want to go into 3rd.

Before I take it to a professional, I will trouble shoot some more this weekend, but can use some tips as to what to look.

Could it be a vacuum leak?
Dual Gate Cable stuck?
Any other ideas appreciated. Thanks in advance.

 

I don't think its a vacum leak or a modulator issue. If that were the case, the trans would stay in first for a very long time before or ever shift into second.

If it were a cable issue you would probably have another symptom..like not going into park or reverse etc.

First...I think you have a sticking valve in the valve body. If it were me, I would continue with a few short drives that insure you get up to full temperature with the occasional manual shifting of the trans. This might loosen it up for this season.

Second, it could be governor issue, But I'd rather wait and see.

 

Have you tried shifting manually? Start shifting to low and then work your way up to 2 and then to drive.
When was the last time you changed your transmission filter?

 

Most accurate way to check a transmissions health is to hook a gauge to the pressure ports and see if the PSI readings meet the specs in all gears including park and neutral.
Could be a sticking governor. Pull it and look at the gear, springs, and shaft.
Could be a sticking 2-3 upshift valve in the valve body?
Could be an internal bypass somewhere due to breakage or worn seals?(rebuild time)
Look at the kick down switch above the gas pedal. If it's sticking it will keep it in 2nd.

When's the last time the fluid n filter was serviced?
What's the fluid look and smell like?
Drop the pan and see how much mud is on the bottom?
How many miles on the trans?
Again, The pressure readings will dictate proper course of troubleshooting and other action.

 

The direct clutch has to come on for third gear. The direct clutch is also the driving clutch for reverse. If it worked fine before, and will back up, and this problem happened suddenly, my money is on a valve body issue. How fast have you had the car before noticing it isn't going into 3rd? Take it out for some hard acceleration tests, obviously let out of the throttle befpre running over the crank! You might try unplugging the lockdown solenoid wire on the drivers side of the trans. Maybe the lockdown switch is stuck?