Several weeks ago, I reported a terrible clunk when my 1984 wagon shifted. Responses led me to a vacuum leak which resolved the issue. I also have noticed that the vehicle has difficulty downshifting, and often stays in high gear at low speeds, even if I exert extreme pressure on the accelerator pedal. In essence, I sometimes start out from a stop in high, which obviously causes the vehicle to struggle under such a load at a higher gear. Where do I start looking, and is this something I can resolve myself with an intermediate mechanical skill level?

Thanks in advance.

 

I guess the answer would have to be "usually". Does the internal valving issue imply I am looking at a costly shop repair?