Is it feasible to have the final drive ratio of a rear diff changed? I've got what should be an LSD FD 4.44 and I'm wondering if it's worthwhile to have it converted to a FD 3.90 (if even possible). If it's possible, what's a good place to have do it? Anyone local? Also, am I right thinking that having an LSD rear is better than having an open rear (main concern is control in snow)? It seems like the LSD's are highly coveted and hard to come by, but 4.44 seems pretty useless.
Its absolutely not worth your time, just swap an entire rear end and be done, with a stock 2.5 rs in NA trim, you wont even notice if its NON LSD or not.
It is possible to do it. I believe all you need to do is switch out the pinion gear or something like that. I know that Chux has done it before, and I can pretty much garuntee that fuji would know something about this.
I've done it. Swap out the ring gear and pinion in the LSD case. Non-LSD cases are not machined for you to get it in there. Also, one must check the backlash on the diff and adjust as necessary. Checking the tooth contact patch is also recommended.
Was wondering more about having someone else do it - how difficult/expensive it might be (compared to searching all over for an LSD diff with the right ratio, since I already have an LSD diff and I've seen more than a couple NASIOC threads where people have just plain given up on finding a used LSD diff). My thought was that since I already have the LSD diff that if it wasn't too expensive I could take/send it in somewhere, have the ratio changed and boom - done. Anyone know a good place that can be trusted with something like this so I could get a quote?
Well, you need about $50 worth of seals and gasket(rough guess) and it would easily take a couple hours to go through it. So at the typical shop rate of $100/hr, you could easily have a few hundred dollars tied up into it.
I did this in my old jeep. '97 Wrangler. Changed both pumpkins ring and pinion. (I had to change both if I wanted to use 4wd). It's a PITA and I would strongly think long and hard before I would do it again. So yes, it can be done but it will require some tools that the weekend warrior might not have. I've never done it on a Subaru, so I'm just going off my Jeep experience. I know in the Jeep world out in montana it would run around $200 to $300 per Diff in just labor to change out the ring and pinion. I don't know how much that applies to the cities, but I figured i'd just give you some numbers to go off of.
Still looking for a shop I'm still interested in at least getting a quote from a shop on this. Can anyone tell me who locally (shop-wise) could be trusted to do this correctly?
I've swapped mechanical LSDs into other cases, had great results. as long as the pinion is left in the case, and the shims match the pinion/ring gear. it's worked wonderfully. now, that was a 3.7:1 donor LSD into a 3.9:1 EA82 case. so I'm not sure how that translates to EJ stuff.... BUT, if/when I buy yours, I plan to try to put it into a 3.9:1 XT6 rear diff. of course, I don't have the XT6 yet....
I was thinking that you should just swap your Legacy rear diff out forthat LSD in the 4.444 case and use your RS axles.
So take the open-diff internals from the Legacy case and put them into the LSD case from the RS and use that + the RS axles? Or are you saying take the LSD internals from the RS diff and put it in the Legacy case with the 3.9 R&P? (Would that even fit - I thought the open diff cases were slightly smaller than the LSD cases) I'm sorry, but I'm not exactly following you. Or should I just run the 3.9 up front and 4.44 in the back.
He means take the actual differential part and put it in the case you need to use. A non-lsd case need a little bit of grinding for the LSD to sneak in there. An actual LSD case has been machined for this already.
