What shifter are you using? Sounds like the tranny is not engaging the main drive gear all the way..If it's a Hurst shifter, there are stops to keep the levers from going too deep into the gears.( Not really necessary with an 833 tranny.) The stop may need backed out. Other than that, you just might have to readjust the shifter or make sure that the side levers are tight on the tranny.