in my service manual it says that the front wheel bearings cannot be removed and re-packed w/ grease. wtf? it says the only way to service them is to replace the hub. i have a '94 cherokee and am planning a 1,220 mile road trip this summer and am not comfortable going w/o knowing my bearings are well lubed. i just got the cherokee w/ 138,000 miles on it and don't know its history or how well it was maintained. are the hubs oil filled or is it just grease?