64 Overlander Interior Roof Vent Fan Vibration

[64Overlander]

I just got my electrical system running. I have 2 vent fans. The one in the rear appears to be an intake fan, the one towards the front near the kitchenette appears to be an exhaust fan. The exhaust fan vibrates considerably when running causing the lifters to close. Is there a way to deal with this? The motor appears to be in place correctly. These fans really seem to move some air. The voltmeter reads 20 volts so it appears to have adequate power. Is this a fan blade issue and if so how do you correct it? I'm trying to stay with original components if possible.
Thanks.