will not down shift...

Have a 1994 LaSabre with 105,000 on it. No codes recorded.
At low speeds and other various speeds transmission will not down shift when depressing accelerator. Other than the above transmission works fine.
What could be wrong?
Thanks.

I have a '90 Lesabre that did this for me, and when it did downshift into first or low gear it would "bang" hard. I found a vacuum connector on top of the engine to have its nipple broken that has the vacuum line that goes to the vacuum modulator on the side of the trans. I believe your 3.8L is very similar in '94 as the '90. Look for this first. Alot of times while working and leaning over the engine(such as doing a tune-up etc.) you can break this fitting.

A trans. shop would murder you on something like this that could be simple fix. I just drilled out the broken nipple and inserted a another plastic tube and it's worked fine now for about 5 years. Good Luck!

Update:
Turns out that the throttle position sensor, TPS, was defective but not setting a code.
Replaced TPS and transmission works fine.