Well, I've noticed quite a few posts of folks doing their birfs and thought I'd reiterate some sage advice many have posted about doing the differential breathers at the same time (or soon thereafter). I had been doing this on trucks for a long time based on the thoughts about sucking water and/or dust into the oem breather and fouling up the gear oil leading to some kind of bad consequence. On the 80, the first thing I noticed was that the plugged breather seemed to be responsible for my inner axle seals blowing and then leading to doing a full birf job just because of the two seals. I routed the breathers based on George Scolaro's website info, tying in the tranny and xfer case ones to one breather mounted up to the top of the DS firewall. I guess I always figured that the oem breather was just a crap design and got plugged from road dust etc.
Well, today I got to see what was probably the culprit and thought I'd pass along the experience to nudge those along that still haven't replaced the breathers after spending so much precious time and money doing the birfs. First, as above, the breather is extended using fuel line to a valve cover type breather (much like a little K&N) and the gear oil is all synthetic and filled to the FSM specs. I was working out in the Coachella Valley of southern CA (Palm Springs area) where the daytime highs are in the triple digits already. I had a full truck of gear and three big guys (all 200+). I had the A/C on high and was late so we were blasting on the I-10 somewhere north of 80 and south of 100. The truck is turbo'd w/315's and stock gears. Ran like this for about 2.5 hours. After stopping I went out later to run an errand and noticed the entire DS wheel well and pretty much everything under the hood on the DS was wet with something. I thought it must have been a power steering hose - nope. Kept looking and finally traced it back to the differential breather! So it probably was not more than half a quart of total loss - don't know haven't pulled the diff fill plug yet - but obviously with the front driveline always engaged it is possible to get the gear oil to move up three feet of tubing and out if you get it really, really hot. So maybe under less stress the oil just makes it to the oem breather and gets it gummed up and jammed. Enough hot runs and you toast your inner axle seals. Just a thought but I had a pretty convincing real world test that made me glad I had done the breather extensions. I'll drain the diffs and refill just to make sure I didn't miss anything. Hope this helps someone.
Cheers
Mike R
Well, today I got to see what was probably the culprit and thought I'd pass along the experience to nudge those along that still haven't replaced the breathers after spending so much precious time and money doing the birfs. First, as above, the breather is extended using fuel line to a valve cover type breather (much like a little K&N) and the gear oil is all synthetic and filled to the FSM specs. I was working out in the Coachella Valley of southern CA (Palm Springs area) where the daytime highs are in the triple digits already. I had a full truck of gear and three big guys (all 200+). I had the A/C on high and was late so we were blasting on the I-10 somewhere north of 80 and south of 100. The truck is turbo'd w/315's and stock gears. Ran like this for about 2.5 hours. After stopping I went out later to run an errand and noticed the entire DS wheel well and pretty much everything under the hood on the DS was wet with something. I thought it must have been a power steering hose - nope. Kept looking and finally traced it back to the differential breather! So it probably was not more than half a quart of total loss - don't know haven't pulled the diff fill plug yet - but obviously with the front driveline always engaged it is possible to get the gear oil to move up three feet of tubing and out if you get it really, really hot. So maybe under less stress the oil just makes it to the oem breather and gets it gummed up and jammed. Enough hot runs and you toast your inner axle seals. Just a thought but I had a pretty convincing real world test that made me glad I had done the breather extensions. I'll drain the diffs and refill just to make sure I didn't miss anything. Hope this helps someone.
Cheers
Mike R