Hard Kickdown Shifting?

[Automobilie]

Hi guys! I recently bought a fixer upper 92 Lumina that wasn't starting. Turned out to be a bad fuel pump. Since I couldn't start it I wasn't able to test out the transmission on it, but I got it for $400 and the body is in fairly good shape.

It had some bad fluid leaks, but the car was full of empty bottles so I'm assuming it had a pretty constant flow of fresh fluid through it. Only one thing of ATF so that might not be too bad. I've got it topped off and have fixed most of the oil leaks (I think....).

What happens is when you romp on the pedal to accelerate and the transmission goes down a gear it does so with a very hard hit from 3-2 and to a lesser degree 2-1. The car seems to shift fine up and down. I don't think it's slipping and I have a filter to swap in once I get the underside degreased. I readjusted the TV cable with little effect, but I also noticed the fluid is 2mm above the full mark once fully warmed up. One guy recommended a solenoid was bad, but I think that'll require dropping half the subframe out to get at.

Looking for advise or suggestions on what else to test and try out. If the transmission will need rebuilt it may just end up a scrapper car as I don't have an engine lift and already put 12+ hours into the intake gaskets.

Thanks!

[1988GTU]

iirc that should be equipped with the 4t60 non E. After inspecting the vacuum lines especially at the vacuum modulator valve, try replacing the vacuum modulator valve should you not find any faulty lines or one-way valves not operating as such.

[Automobilie]

Didn't replace the modulator as NAPA want's $30 for one that doesn't look anything like the original one, but I did a vacuum test on it and it held a vacuum. Vacuum off the MAP sensor was around 18psi idle, I replaced the little hose that goes to the modulator that was cracking, seems 2-1 is a little better.

I also removed the pan, still need to a get a filter that fits, pan was VERY clean and free of debris.

Something we did notice was the dogbones were worn down quite a bit. Not sure if that would cause the slamming. Ordered a couple new ones, should be in tomorrow.

[Automobilie]

Update:
So I replaced the filter/fluid wit Dextron IV (Synthetic for Dex-II I believe) as well as the torque struts which were very worn out. Took it for a test drive and couldn't get it to shift hard! So as of now, I believe the Torque struts were the problem.