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Old 01-31-2013, 10:40 AM   #23
Butt Dyno
Street's closed, pizza boy
Member#: 17301
Join Date: Apr 2002
Chapter/Region: MAIC
Location: NoVA
2016 FoST ST3
2006 Evo #17 STU

Default Aftermarket rear differentials in ST*... good idea?

The diff rule in ST currently:

K. Limited Slip Differentials
STC, STS, STF No limited slip differentials are permitted except for
factory standard viscous coupler type units.
STX, STU, STR Only standard (as defned in Section 12.4) limited
slip differentials (LSD) are allowed on AWD vehicles. For AWD
vehicles that did not come with any type of limited slip differential
(including center differential or transfer case), a single aftermarket
LSD may be added.
2WD vehicles may use any LSD unit.
For WRXs in STX, and STis and WRXs in STU, what would you think about opening that up to allow AWD vehicles to change/add one aftermarket LSD?

In other words:
-If you had a WRX you could swap out the rear viscous for a clutch type
-If you had an 07+ STi you could swap out the torsen for a clutch type
-If you had an Evo/04-06 STi you could just put a nicer rear diff in

Near as I can figure, this would not impact STR at all, it would make the WRX more competitive in STX but not overly so, and would probably increase the range of competitive cars in STU (the Torsen cars and the 09+ WRXs would have a better shot at things). Evo IX's and 05-06 STis are going to slowly die off, so this might set the class up better for the future.

It would likely become a must have mod for those cars though, which has a range of expensiveness, and opens up more ground for tuning. That said, STR has that problem as it sits, nothing stopping people from dropping coin on an OS Giken diff or whatever. And they are okay with it. They didn't need to make that allowance since the target cars (S2K, Miata) were available with Torsen limited slips, but they did.

What say ye?
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