I had an Auburn limited slip posi unit installed (before I actually installed the rear). I filled it with synthetic 80w90 gear oil. I have some chattering. After looking at Auburns website, they recommend non-synthetic 80w90 with the limited slip additive. Anybody ever drained an eight inch rear? I was thinking about the options. Is it possible to just crack the nuts loose to let the oil seep out? Or, has anyone ever drilled and tapped the bottom of the housing for a drain plug? I worry about drilling in too far and damaging something when the bit initially pops through. Sometimes no matter how careful you try to be it happens. Or, I'm considering just putting in the additive in and seeing if I get any results that way. Any suggestions?
If its not leaking you could get a fluid evacuator from harbor freight and suck out all the fluid, then replace it with the right stuff.
Thanks, I have a Harbor Freight nearby. I might do that. After reading your reply I looked on their website check it out.http://www.harborfreight.com/multi-use-transfer-pump-66418.html
For those of you that recommend just adding the additive to the synth oil using the vent hole. Have you ever used the vent hole to insert an additive? I'm wondering if there is a lip there that could keep the fluid from running into the gear housing area and without tilting the car it could just be trapped in the axle housing?
There is no lip the differential flud travels through the whole housing when in use You will have to screw the fitting out of the housing but this is also a good time to make sure the vent fitting and hose are not plugged
One time when I had my rear apart, I drilled and tapped a hole for a plug. Never used it, yet, but it is there if I ever need to.
Just drill a hole in the bottom of the housing and let the oil drain out. Once that's done, then tap the hole for a pipe tap and install a drain plug. There's nothing inside that you're going to damage, there's no worry about filings either, what few may end up inside will come out with the oil. Even if you do get anything stuck in there, you're talking about softer steel than all the internals, it would take a lifetime of continous use before anything bad would have a chance of happening. I would drill for a 1/8" or 1/4" sized pipe tap. And don't get wild with the drill when you do the job, at worst all you'd do is nick the ring gear, it wouldn't be enough to damage it though.
I think i did 1/4". The first plug i used had a large square protrusion, like the plug on the side of the trans. Got in the way when jacking up the car by the diff. Next plug had a allen shaped hole, so it sits fluch to the bottom of he diff.
Ok, good to know. I'm going to try adding the friction additive right with the synthetic oil and I'll let you all know how it works. If I definitely have to drain it then I'll use a pipe thread tap as you mentioned, thanks.
