TPS or Trans Issue?

I am new to this forum but not to cars in general. I have gone through the site for quite a while but can't find the info I'm looking for. I picked up an 88 Accord Lxi 4dr auto with 113k on it for my son for college this fall. I have gone through and replaced all the front end bushings/bearings, upper and lower control arms, new ball joints, brakes front and rear, along with the drums and rotors, new plugs/wires/cap/rotor, changed oil/filter and trans fluid.

My issue is while driving, it will shift from 4th to 3rd at the slightest release of the gas pedal no matter what speed I am at. I can keep pressing the pedal and it will stay in 4th gear but when I get too far over the speed limit I have to back it off a little and it will shift down to 3rd. Is this normal for the car or is there some checks or tests I can do to see where the actual problem is? Any help is appreciated.

Definitely not the TPS as the trans is entirely mechanical/hydraulic. There's no wiring anywhere on it. You want to check the mechanical equivalent of a TPS, which is the TV cable. It's a long cable that extends from the throttle body butterfly down to the trans. Sounds like it's out of adjustment to me, though downshifting when you let OFF the throttle is very unusual.

Thanks Snooz, I have the FSM so I will go through the adjustment process for the TV cable, I appreciate the input.

Snooz - I adjusted the TV cable and that seemed to do the trick. I need to fine tune it a little because it seems to shift somewhat odd but might just be me getting used to the car.

I appreciate the tip on that adjustment.

Just like as with a newer car, make sure the throttle body is good and clean and base idle/ base timing is sweet BEFORE saying work on transmission shift points and TQ conv lock up is squirrely .

Thanks 2oodoor, I will go over these items as well. I did clean the idle circuit that sits on the side of the throttle body but all I had was carb cleaner so I didn't do the throttle plate yet, it needs it bad. I will go over timing also.