I've got a 1990 Accord with the automatic transmission. It shifts really hard if you drive it normally, but if you let off of the gas right before it shifts it's like nothing is wrong and it has problems selecting what gear to be in. I've been looking into whether or not there is some type of band adjustment, but found some info that said the TCU (Transmission Control Unit) has a lot of problems in these years. Any thoughts as to whether this piece could be the problem?

 

If the S light starts flashing or the D4, then you should look up error codes. There is a writeup in the DIY section on how to check CEL codes.

There is a cable that goes from the throttle body to the transmission that you can adjust the tension.

Copy and paste the link below into your browser for that adjustment

media.honda.co.uk/car/owner/media/manuals/accordManual/400/9-88.pdf

Here is an adjustment for the gear selector.

http://media.honda.co.uk/car/owner/m...l/400/9-88.pdf

Also, when did you last do an ATF drain/refill? Use honda ATF when doing this. There is a video on ericthecarguy.com that has this information. Just google ericthecarguy transmission fluid to see a good video.

 

Did the drain and refill a few weeks ago. The hard shift is only from first to second gear as well. I forgot to mention that.

 

Check your fluid make sure it's full, check for code, you could try adjusting the TV cable like PAhonda said, if all that did not help then your 2nd clutch accumulator piston or sealing ring worn/damaged, or sticky 2nd clutch shift valve in the valve body, all this could only be fix during an overhaul.