The shop manual shows a drain plug for the front differential on my 95 S-10 PU. I like to change the gear oil every several years and each time I end up sucking out what I can thru the fill plug. I can't find a drain. Even tried removing a couple of the lower case bolts thinking maybe they acted as a drain. No luck. Anyone have knowledge if GM put a drain in these trucks?.. or more generally, how do you drain the front differential?