i have a 1999 durango, 5.9L, 4x4, auto.

Problem is about half the time the starter motor will spin but won't turn over the engine. sometimes it does work fine. solenoid does push the gear out because i can see scratches on the face of the flywheel which is in good shape, no missing or worn down teeth.

i have replaced the battery and the starter is brand new. this has me baffled and any help from someone wiser than me will be appreciated. thanks in advance.

 

Why is the starter brand new? Did the old one do the same thing?

 

Really shouldn't see scratches because the teeth on the stater should engage the ones on the flywheel before it starts to turn. Do you have a good ground on the motor? As JeeperDon asked, did the old one do the same?