84 300D shifting too early

[Lenovolost]

I have been trying to get my 84' 300d to accelerate up hill and its been a nightmare. The turbo is working, fuel filters replaced, ALDA banjo at intake has been cleaned, injection pump cleaned with sea foam. The only thing that is driving me crazy is that the transmission seems to be shifting into 2nd then 3rd very quickly. I tried adjusting the cable on top of the valve cover but had no noticeable results. Not sure what else could be making the trans shift too early and not allowing me to speed up with a little turbo help.

Any thoughts???