I'm in a tight spot. I am supposed to be leaving tomorrow at noon on a 300 mile trip. I can get the fill plug off the low range and it is low but I can't get the fill plug out of the tcase itself. I tried everything(heat, pb blaster) and I am running out of time.
My question is, can I fill the low range unit, drive figure 8's, check and refill as necessary and repeat?
They do share the same oil, the proper filling would be to fill the low range until the oil just runs from the fill port, then fill the main case until oil runs from that case. I believe the oil that is lost by the gears moving in the low range ( it just runs into the main case) is replenished by the oil coming of the chair as it goes around .
If the main case has enough oil, I wouldn't be overly concerned.
The problem your having is due to the steel plug, in a aluminum case. It's a dissimilar metals thing.
The first time I ever filled my low range unit, I way over filled the main at the same time. I kept putting oil in as it was running out the low range . When I checked the main case all the extra oil I put in the low came out.
1957 WILLYS pickup,
1973 J 4000,
1978 CJ7 DD.
1979 CJ7 360, TH400/Quadratrac.
1980 CJ5 trail Jeep.
1989 YJ the CJ to YJ.