it has to have to much fluid and is whipping it into a pressure point and forcing it out the vent---check with your center section maker--the mass size might have alot to do with the amount you put in the rearend housing---just also try lowering the fluid in the housing and run it again
ops:
make sure the vent fitting and line both come out of the TOP of the housing straight up not at an angle 8)
i had that vent angle problem on a mud truck 9 inch and that was causing a syphoning problem of the fluid :cry:
let us know what you try and the results 8)