Hello, i replaced the traction motor in this unit. i installed a new drive gear on the motor because the old gear had a partial tooth broken. After putting it together it is making a loud whining noise. the gear is the correct part number for this unit. the dipstick is showing full. i was looking for the fill plug on the diferential (drive unit) i only see one on the plate at the bottom. I'm wanting to check the gear oil at the drive unit. s/n ET-B-96-02732