The fluid change itself is pretty easy as long as you have equipment needed to do it, good way to save some $ and make sure it's done right. If you are going to pop off vent for cleaning or RnR, hit the shelf it sits on with a small paint brush so any crud on there doesn't fall in. It looked like a ratchet with a deep socket might also work with swing room available above diff, just need a socket with straight internal walls to clear cap. Tight, so I left it alone, didn't want Murphy putting in an appearance with me not having a replacement on hand if I broke cap off it.'

I put an offset wrench on it and tried to loosen it. 14mm just starts to go on, it but doesn't go all the way on. But there has been some confusion as to size of wrench needed to remove vent, some saying it's a 16, others saying that didn't fit. 'My vent has always been clean, never had to mess with it, cap nice and loose riding on the spring. PN as listed in Sergio's post still available at numerous places online, including Ebay for same 21 bucks shipped I paid. LSD diffs require a fluid with friction modifier so you don't get diff clutch chatter around corners. That's how it was done on 10 and 12 bolt GM diffs. So filling to the drain hole is probably fine. When I filled, I stopped when fluid just started to drip out of fill hole. Unfortunately I missed some of the fluid, maybe a couple ounces, so didn't get an exact reading. I then took an empty oil quart bottle, popped a small funnel on it, and opened up the drain. So 1st time I did it, I removed the fill plug and stuck my finger in there to check level. I thought I read somewhere that the LSD diff was larger? Click to expand.The 1st link in my post lists capacity for diff with LSD at 1.0 L, but I could not find anything specifically for the open diff as used in my Lux.

Leaking differential fluid