Hard Shifting and No Power @ the wheels

[RichardsD]

Long story short, bought a 92 SVX LS-L as a long term project, which did not run when I bought it. Did some basic maintenance and a few replacements and it fired up shortly after. I've been fixing slowly the large amount of problems resulting from being a 25 year old car that wasn't driven for the last 4 years. Anyways, it is now at the state where it drives and the engine runs nicely.

However, the transmission doesn't seem up to the job currently. I ensured that the ATF was flushed and re-filled, and re-did the pan gasket. Now that I have ATF and no leaks, it seems a bit rough. Firstly, it will "chirp" all 4 wheels when engaging first, and "clunks" into gear. Shifting is also rough, although once I start driving it becomes a bit smoother. However, the main issue is that there doesn't seem to be a lot of power actually making it to the wheels. On flat ground it seems fine, but the shop where I work on the SVX has a slight incline to enter. I cannot enter without a long run-up, as the RPMs will increase, but there's no power to get up the hill (and it's not much of a hill).

So, clearly something isn't too great. And although I can fix something, the whole diagnosis part isn't too easy. I'm no expert on automatics, but my understanding is a torque converter acts similar to a clutch, in that it could slip if worn. Thus, creating my problem. The car doesn't have a aftermarket trans cooler installed as well, and I know that overheating is a big problem. And this has 256xxx kms, so it could definitely be worn out.

So, I need some advice on what/how I should address this. If it's a full new treansmission, don't most people use later 4ATs from other Subarus? If so, which one? And could it be just the torque converter?

Thanks!