I just bought a 94 Bonneville Se witha problem downshifting. It won't downshift unless you do it manually. From a start or passing
It also has a shudder in low gear if you stomp it.
IT shifts fine as long as you move it to low gear then move it back to OD
I hooked the scanner up and it shows no error codes and no pending codes.
I also monitored it to make sure when i put the selector in each gear that it was showing the correct gear.
Transmission is a 4t60 F17 2.84 gears
car has 163k miles
any suggestions.

have you tried to adjust your TV cable yet?

its showing the correct gear....

umm have u checked the trans fluid....and the level of the fluid....interesting that its not throwing any codes...

Also im thinking the TPS may be a cause of this, I TPS with a wacky paramater can cause the trans to shift incorrectly or not at all

I checked the fluid and it'* full. I never replaced the filter yet. I never adjust the cable yet either. I will check it tomorrow. I will also try to check the voltage on the TPS and see what it shows.
I also noticed that sometimes when it'* in park or neutral the torque converter sounds like it tried to lock and unlock. It quits doing that when you put it in any forward gear or reverse.