1992 Volvo 240 automatic won't shift out of 1st gear

I just picked up this old 240 wagon with 230k miles on it for next to nothing due to a transmission issue. It stays stuck in 1st gear for about the first 15 minutes of drive time and then starts shifting perfectly after that. I took it to a transmission specialist and he thought the valve body may be sticking. I also had an experienced volvo tech adjust the kick down cable but so far its still having the same issue.
Any idea’s would be greatly appreciated as I would really like to turn this into a daily driver but am concerned it may need an expensive transmission rebuild.

The vehicle is a candidate for this stuff.

Let us know if it works!

Tester

Do I have to remove some fluid to make room for the additive?

Read the KEY BENEFITS again.

Tester

I would change the fluid and or trans filter if applicable…and then do what @Tester suggested. How does the current fluid look…and smell ? If it shifts proper when hot…you know it has the ability to function properly…so give it a fighting chance with fluid, filter and additive…

Blackbird

I would change the transmission fluid and filter first and see if the shifting improves. I tried the Lucas product but only got minimal results. I finally added a can of Berryman’s B-12 Chemtool and it worked like a champ. I’ve used this product several times and always got great results.