Good Evening,

I found an earlier post (2004) on this topic but no clear solution.

Any ideas on why my auto trans won't downshift to 1st gear when
manually placed into 1st gear? It will limit itself to first gear
only when accelerating in 1st gear but it won't allow engine breaking
to decelerate on decents. It seams like it is in neutral when no gas
is applied, allow
it to coast and even pick speed on a steep decent. 2nd gear
functionality works fine including engine braking.

I have experimented with it enough to know that it is a real problem,
and not related to high-speed shifting in to 1st.

Any help is appreciated. Thanks!