My current car had a Dana 60 with one of the Ultimate covers with no vent, it had a 1/8 inch NPT brass plug above the passenger side of the spool at the top of the cover so I put a 1/8 brass NPT pipe nipple in there and added some neopreme flexable tubing so it, the top of it, is higher than the top of the Dana now to vent it It has the Mark Williams 40 spline axles and aluminum spool and all the other M.W. good stuff, why it didn't have a vent is a mystery to me, it did not leak or weep, even with 5.86 gears in it at 7700 RPM in high gear Years ago at one of the Mopar drag seminars they recommended using one quart of rear end lube only in both the 8 3/4 and the Dana 60 for drag racing, they said, Tom Hoover or L.S, CRS, that the production fluid levels was set so high to help keep the noise down for the average car buyer I ran one quart for a lot of years in both my Dana 60 and 8 3/4, even with posi uits in both I did put 5 pints in the current car, it had the synthetic Redline lightweight green shock proof gear oil in it so I bought 2 new gallons of that and used it I bought some of the synthetic Redline high strength shock proof red heavier weight also but I stuck it in the car trailer for future use, if needed