1964 st400 shfts

Hello everyone. I have a 1964 Riviera with the ST400 trans. I have a question about the shift points on my car. As you all know the ST400 is a 3 speed. My question------When I step on the gas no matter how easy or how hard my 1-2 shift is always around 15-20 mph. Is this right. Should the trans wind out if I accelerate harder for the 1-2 shift, the other shift seems fine. If this doesn't seem right please let me know fix. Buicks are new to me so ignore my ignorance. Thanks to everyone in advance for your help. Ray 

Although I was born in 1964, I hadn't started working on cars until the 1970's. I haven't worked on a car that old in a long time, but I believe that tranny should have a detent cable or detent linkage. It would hook to the carburetor throttle linkage and go down to a lever on the transmission. At wide open throttle, or close to it, this will also give you your kick down from 3-2, and 2-1 gear. It should be adjustable and may just be your problem. I will research it a little further to see if I can give you a definitive answer.

bigdave wrote:

Although I was born in 1964, I hadn't started working on cars until the 1970's. I haven't worked on a car that old in a long time, but I believe that tranny should have a detent cable or detent linkage. It would hook to the carburetor throttle linkage and go down to a lever on the transmission. At wide open throttle, or close to it, this will also give you your kick down from 3-2, and 2-1 gear. It should be adjustable and may just be your problem. I will research it a little further to see if I can give you a definitive answer.

Thank you Dave

I found some good info on the ST 400 for you. I hope this helps.http://www.buickperformanceclub.com/SPTrans.htm

I don't think the 400 has a detent cable, that was the 350. I thought the 400 used vacuum.

I would put a vacuum gauge on it and make sure you are getting to 0 vacuum at full throttle. Also check the lines going to the transmission for vacuum leaks, and lastly take the vacuum modulator out and test it.

There are also governor springs and weights inside that could be worn out after so many years. I believe they are behind the speedo gears but would need to confirm. I'm pretty sure thats where they are on the TH400, I believe the ST400 is basically the same thing.

The V8Buick boards, BCA and BPG all have a lot more tech info for you.

To add to Derek's info:

www.v8buick.com (more tech info than you can imagine)
www.buickperformancegroup.com/forums

Here are some governor spring kits that list the TH400. You would want to confirm if they are okay for the ST400 first though.

http://www.summitracing.com/search/part-type/automatic-transmission-governor-recalibration-kits

Thank you everyone your help. Ray