Supra LSD
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Lexus Test Driver
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From: Baton Rouge, Louisiana
Also, would it be a good idea to go from my 4.08 (5sp. diff), to a 3.76 ratio? Would this be a BIG difference. I would want to kill the little bit of take off power, I have now.
Should I hold off for a TT diff. or aftermarket, so I can keep my ratio?
Should I hold off for a TT diff. or aftermarket, so I can keep my ratio?
That is absolutely a Supra Torsen LSD differential. The 3.76 gearing is from the Auto TT Supra.
The 3.76 ratio is about 10% more conservative than your current gearing. You would absolutely be able to notice the gears being longer. Longer gearing would improve highway fuel economy, but it would also minimize the amount of perceived torque that would reach the road.
In general, longer gearing is only positive for performance when traction or turbo lag are significant issues (often these go hand in hand). The longer gearing will minimize the number of shifts to keep a big turbo in boost longer once it has spooled. It will also better ensure that the tires are on the road.
I spent many hours and a nice chunk of change to rebuild an LSD differential with 4.27 gears for the performance gain over the 3.92 gears that my SC400 has in stock form.
In my opinion, this upgrade would be somewhat counter-productive in nature. The LSD would definitely help keep the car grounded, but the gearing would neutralize the increase in launching power off the line or in the twisties.
If you are going to run a 67+mm turbo on your 2JZ, the gearing may become a positive thing. But, otherwise, expect to really only gain traction and fuel economy while hurting your times fractions of a second from the gearing.
The 3.76 ratio is about 10% more conservative than your current gearing. You would absolutely be able to notice the gears being longer. Longer gearing would improve highway fuel economy, but it would also minimize the amount of perceived torque that would reach the road.
In general, longer gearing is only positive for performance when traction or turbo lag are significant issues (often these go hand in hand). The longer gearing will minimize the number of shifts to keep a big turbo in boost longer once it has spooled. It will also better ensure that the tires are on the road.
I spent many hours and a nice chunk of change to rebuild an LSD differential with 4.27 gears for the performance gain over the 3.92 gears that my SC400 has in stock form.
In my opinion, this upgrade would be somewhat counter-productive in nature. The LSD would definitely help keep the car grounded, but the gearing would neutralize the increase in launching power off the line or in the twisties.
If you are going to run a 67+mm turbo on your 2JZ, the gearing may become a positive thing. But, otherwise, expect to really only gain traction and fuel economy while hurting your times fractions of a second from the gearing.
Last edited by Blizzy; Sep 2, 2007 at 11:21 AM.
that ratio is for the TT Manual Supra (in Japan). It is ~3.1 here in the states.
With the differential open, it is easy to tell which is which by counting the bolts around the ring of the differential. 12 bolts is for the 6spd, 10 bolts is for the Auto TT (and the SC).
But, if it is a 3.76 ratio, it can only be the Auto TT differential, which directly swaps to the SC's rear end. My opinion has already been stated about this above.
With the differential open, it is easy to tell which is which by counting the bolts around the ring of the differential. 12 bolts is for the 6spd, 10 bolts is for the Auto TT (and the SC).
But, if it is a 3.76 ratio, it can only be the Auto TT differential, which directly swaps to the SC's rear end. My opinion has already been stated about this above.
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