If you lose all gears, it sounds like you are losing line pressure. Have you been able to check that? Also, have you checked to make sure there aren't relevant diagnostic trouble codes related to the transmission?
I attached the directions below for testing line pressure. Let me know if this is something you are comfortable performing.
Take care,
joe
See pics below.
Images (Click to make bigger)
SPONSORED LINKS
Thursday, June 1st, 2023 AT 10:15 PM