Sabaru transmission downshift

my 1999 sabaru transmission downshifts from 4th to 3rd all by itself only when going downhill. whats going on?

This sounds like the “fuzzy logic” that is programmed into the transmission controller is doing its job, in order to provide engine braking on a downgrade.

You might want to check the SUBARU Owner’s Manual, as it may discuss the concept of fuzzy logic regarding the transmission.

Good question. Consider asking it at if your owner’s manual doesn’t agree with VDCdriver. Personally I think it will.