If you are interested in a core refund- email us for more info. This requires an RMA# to be issued to you with your order. You must purchase the GSR LSD Conversion Kit at the same time with the GSR Gear Set and return your original OEM GSR gears back to us with your Return Material Authorization # within 14 days of delivery of your order. Your 4 OEM GSR gears must be in good condition without any broken teeth, cracks, or chips to be eligible for your core to be accepted. Once your GSR gears are inspected, you will get $199.00 refunded back to your method of payment. Shipping is paid for by the buyer and not refunded.