stock bg5 rear diff to lsd 4.11 or 4.44 swap?

[bg5enthusiast]

I was looking into going into a jdm lsd swap for the rear, but need to know how to make 3.46 to 4.11 fd work?

[bg5enthusiast]

sorry, correction. I need to find a 4.11 to 4.44 swap for lsd. any ideas?

[Sarra]

If you WANT a 4.444 final drive rear diff, then you will also have to swap the front diff.

otherwise, you just take it apart, keep the shims in their correct places, and swap the limited slip part over, and leave the ring and pinion alone.

There's a lot of preloads, clearances, and the shims to deal with in a diff. If you have never swapped guts before, then I'd suggest you take it to a dealership and tell them what you want to do, and have them do it for you.

And as I mentioned, if you have a 4.111 final drive right now in your car, and you simply put a 4.444 final drive rear diff in your car, you will destroy your center diff. If you have a 4.444 gearbox or are swapping front diffs, then go ahead. Or are you just sourcing the Limited Slip part from a 4.444? You could also use a 3.9, 3.545, or any other Subaru LSD rear diff other than one from an STi for just putting LSD into your stock rear end.

[impreza_GC8]

General rule of thumb is to match the tranny with the rear end. If you want to use a 4.44 FD LSD you need to source a 4.44 transmission too which could prove a bit difficult seeing as those were only available on some JDM STIs.

[bg5enthusiast]

well in that case is there any way I could mate my usdm ej25 with any lsd setup?

[impreza_GC8]

Yes there are many viscous LSD type 4.11 rear ends around. They came on the Impreza 2.5RS in model year 2000 and 2001. They might have the same drivetrain in 2002 and 2003 but I don't have much experience with that chassis so I wont comment for sure. There are also some JDM rear ends floating around too but your best bet would be to get from a USDM RS Impreza.

[Sarra]

Yes there are many viscous LSD type 4.11 rear ends around. They came on the Impreza 2.5RS in model year 2000 and 2001. They might have the same drivetrain in 2002 and 2003 but I don't have much experience with that chassis so I wont comment for sure. There are also some JDM rear ends floating around too but your best bet would be to get from a USDM RS Impreza.

I don't believe they had an LSD in 2002-2003. :(

[impreza_GC8]

OK after some research it seems that Subaru did carry the 4.11 drivetrain over to the 02-03 RS but it seems the car was not equipped with an LSD, suprising they would revert back to a non-LSD 4.11 drivetrain but whatever. So your best solution is to get one from a 2000 or 2001 2.5RS. Bear in mind it will be a viscous LSD unit which is not a very effective LSD, especially as they age, but it is an improvement over an open diff. I own both and despite what people say about there not being much difference I can most certainly feel a difference from my open diff car to my VLSD car on gravel and snow as well as spirited driving in the rain.

[Sarra]

Why did they switch back to an open rear diff?

Two reasons. First would be money, it's an additional cost to make them, and drives the vehicle's MSRP up, even if slightly. Second is gas mileage. Probably infinitesimal, but an open diff has less parasitic drag when you're going 55-70 on the freeway around a turn. So, you save slightly on gas mileage.

[99gtlimited]

i believe 02-03 USDM WRX (maybe newer ones too) with AT have a 4.11 LSD in the rear, that would be another place to look.