Rear 4.111 LSD (w/ JDM 4.111 trans) - how to tell what type?

[free5ty1e]

Hey hey!

So, I just changed out Uncle Scotty's 5MT Cocktail for some Valvoline 75W90 limited slip gear oil (read up on some worrying posts about the USC and when cold I have been feeling the drop in lubrication). I had replaced my stock 5MT with a JDM 4.111 5MT + rear 4.111 LSD a couple years back and am wondering how I can tell what type of rear differential I have?



I believe this photo shows the fill and drain plugs on the rear face of my diff, which I still have to find tools to fit and remove... how do I tell if I've got a viscous coupling LSD or a clutch-based LSD back here? This is mainly so I can then figure out what gear oil I should refill with. I figure I should probably change its oil along with the trans oil so they are about the same age.

Here's my ghetto-fabulous Subaru Maintenance Dock as I could not completely drain the trans with the front on ramps and I could not physically reach the trans drain plug with the rear on ramps. Thought you guys might get a kick out of it:

[BSOD2600]

Whats the part number stamped on the rear diff? once you have it, look it up on google.

[Legacy777]

Almost all subaru rear LSD's are the viscous type, which is most likely what you have. You can use any appropriate diff fluid in it.

There should be a tag on the back diff cover. If there is not one, look on the webbing for a mark/stamp. Check out page two of this pdf for an idea of what I'm talking about.

http://main.experiencetherave.com/subar ... f_info.pdf

You should be able to use a 1/2" drive socket to remove the diff plugs.

[free5ty1e]

Yeah, no labels or tags anywhere. All I could find is the stamped info on the bottom face of the diff. Here is a pic.

The only other marking is a blue "4.11" handwritten on the rear face (the face with the drain plugs) but I went under there and scrubbed gunk off looking for labels and could find none...

Any ideas? I'm pretty sure this is a VLSD.

[Legacy777]

Unfortunately, I don't believe that info on the bottom part has any real bearing on what's inside the diff. It's more of a casting number.

[vrg3]

Silly Subaru, putting all the important information about the differential on a freaking sticker. That diff's sticker is obviously long gone.

I didn't think Subaru ever used clutch-type rear differentials on the Legacy/Impreza/etc platform, but I may be wrong. In any case, this page about swapping Subaru LSDs into Datsun 510s says:

Drain the fluid from the differential and peek inside through the fill or drain hole with a flashlight. The clutch-pack LSD unit looks different from the open unit. You could also stick a finger inside the fill or drain hole and feel the difference between the two. The clutch pack is pretty obvious. The internals of some Subaru viscous LSD units will look the same as an open unit, as the viscous plates are hidden behind the ring gear.