From your description it sounds like a transmission issue. Check the transmission fluid level. Do this after engine has warmed up and the vehicle is on a flat level surface with the engine running. Check the condition of the fluid also. It should be red and clear. Recommend changing the trans fluid if it is brown/ dark not very clear looking.
It sounds like the trans fluid is low and that is why it only happens on an incline. The transmission oil pump is possibly sucking up air due to the low trans fluid level causing the transmission to slam into gear or not propel the vehicle normally.
This guide ca help as well
Thanks for the question. Please run down this guide and report back.
Tuesday, April 13th, 2021 AT 6:46 PM