I'd like to know this so that when I look at ads I can tell if the car has one. I really want one for my lifted Loyale and am willing to buy a whole car to get one, especially if it is a fuel-injected 86 or newer wagon. Then I can use the D/R 5-speed and have a spare motor too, plus all the little nickel-and-dime stuff. Basically my own compact junkyard.

try doing a search, you'll get tons of commentary on this subject.

 

easiest to get a 3.7 lsd and convert your existing open 3.9 using the internals of the 3.7. i believe there's information and a write up addressing this. do a search on this group and you'll have plenty to read for quite some time, with lots of lists of vehicles...

The parts books say that a 3.9 LSD was an option on the XT6 but no one on the board has actually seen one. All of the other LSDs will have a 3.7 ratio. Here's what's involved to take a 3.9 and making it an LSD using 3.7 LSD parts.

 

http://www.ultimatesubaru.org/forum/article.php?a=36

The parts books say that a 3.9 LSD was an option on the XT6 but no one on the board has actually seen one. All of the other LSDs will have a 3.7 ratio. Here's what's involved to take a 3.9 and making it an LSD using 3.7 LSD parts.

 

http://www.ultimatesubaru.org/forum/article.php?a=36

Correction, the parts page at Liberty Subaru states that, my Subaru Parts Book only shows that parts as a LSD rear diff, it doesn't give the ratio. I sent Liberty an e-mail asking them to verify that part number as being a 3.90 ratio. I'm not surprized that they haven't answered.

The parts books say that a 3.9 LSD was an option on the XT6 but no one on the board has actually seen one.

 

I've seen one. It was on/in a XT6 on it's way into Aaron's Auto Wrecking. Couple years ago.

best bet is to build one from a 3.7 lsd unit and an open 3.9.

 

keep your eye on ebay as well, but they'll go for 300+ and i've seen 2 in the past 2 years. you will likely wait a long time before you see one on there though.