Lex Luthor

Can anyone confirm that the SC400 has a Torsen LSD either as standard or as an option? Mine leaves two tyre marks, the SC3 guys tell me they never spin more than one tyre, but i've known an LSD to spin only one tyre sometimes, as opposed to a positraction or trak-lok that would always leave two even tyre marks.
- Jon

wwest

Except for the early RXes, and the LX, I don't think any Lexus comes standard withy any sort of mechanical LSD, the electronically implemented TRAC supplants the need.

Slick Lex Coupe

I think that you can tell by jacking up the back of the car and then manually spinning the tire. If the other wheel spins too then you have an LSD.

cupete

What's the benefit of having LSD?

SC300T

If you jack up the back of the car with it in gear (manual) or in park (auto), and try to spin one tire forward, if the other one spins backwards, you have an open diff.

I can paint two long black streaks even without an LSD. If the traction is nearly equal on both sides and they both break loose at the same time you can get it to spin both tires.

To my knowledge, no SC400 has ever been equipped with a torsen LSD (not enough power to need it). The N/A MK4 Supra had a clutch type LSD available as an option on some years, but the only SC300/Supra type that had a torsen type stock was the TT.

Cupete:
The benefit of a Limited Slip Differential is that you can apply up to 100% of your torque to the wheel that needs it... With a torsen type, it will apply this torque to each wheel's limit independently. For instance, if one wheel could accept only 30% of the engine's torque due to slippery surface on one side, it will try to apply the remaining 70% to the other wheel if possible. If the torque exceeds both sides potential, you will still slip, but you will have used every bit of traction available. When aggressively accelerating, there is usually one wheel that has less pressure (weight) on it due to twisting force that the engine exerts on the body of the car.

Lex Luthor

Scott, read a review that said that the Soarer V8 had a Torsen LSD, that's what got this started, but I guess it was just wishfull thinking. Eh, I won't need it until I drop a GTE in there anyway, it'll be funny driving around with SC4 badges.

SC300T

Do you know the ratio on that?
I'd be interested if it would be a drop in replacement for the US version of the SC300.

It may actually be the same part# as the Supra TT auto diff. The TT Soarer probably has some sort of LSD as well, but since they're not available here I don't know much about them.

MadMaxSC400

I'm going to buy one and find out how to put it in, if I turn left and hit the throttle a bit, I burn, same with turning right, from a stop, rolling slow, it's a really annoying problem. I have a considerable amount more tread than I used to have with my wider rims, but with the last chip reprogram the problem's come back.

SC300T

I thought RMM carried some LSD options for the SC3/4.

I also remember seeing something on the Powerhouse Racing website about changing the ratio on the LSD.

Dave H had the TT differential from the automatic Supra TT... Said it bolted right on.

On the SC400 (auto), you have to watch out about ratios, cause the automatic uses Vehicle Speed Sensor data to adjust shift points. If the ratio is too high, your actual speed will lower per rev and you'll bump the rev limiter on full throttle shifts. Ideally if your ECU is massaged to allow higher red-line, the LSD would compliment it to take advantage of the higher shift point. This is especially true if you've done some work to improve high rpm breathing---significant gains could be had from this combo.

Lex Luthor

Well, as far as ratios, i've been told the SC4 is a 3.92, haven't marked my driveshaft and checked yet. The SC3 is actually steeper supposedly, a 4.08 ring and pinion. Again, I haven't checked this. If I remember right, the Supra 6spd is a 3.13, anyone know the ratio on the Supra auto?

MadMaxSC400

We'd been playing with the idea of raising the reline on the car.. does anyone know what the limits are? Any project cars turning at 7k or higher? I will likely use the RMM unit because it's got the right gearing, although I hate paying their ransom.

'S'Low Rider

These are the specs for the JDM Soarers, I doubt that the US spec SC's are any different.

I swapped over the diff from the Soarer Twin Turbo (JZZ31) to my V8 (bolts straight on). I would say it feels a little more 'sparkier' but difficult to say how big an improvement......

So an SC300 diff should bolt straight on......

Differential Final Gear Ratios

UZZ3* 05/91 - 07/91 3.916 (SC400)
UZZ3* 07/91 - EOP 3.917 (SC400 upto 1997, I dont know about the vvti model)
JZZ31 07/91 - EOP 4.083
JZZ30 07/91 - 08/96 4.083 (SC300)
JZZ30 08/96 - EOP 4.083 MTM (SC300)
JZZ30 08/96 - EOP 3.917 ATM (SC300)

The MiNes ECU upgrade from Japan gives you 7500rpm. I only know one guy who has this upgrade. But he's had it for 3 years and his comment was that the V8 "is smooth and well balanced right up to this point".

SC300T

RE: high RPM V-8:

I'd love to see someone do this:
Port and polish the heads ($1000-$1500). stiffer valve springs (should be easy $400). Find a way to raise the compression slightly (custom head gaskets? $?). Headers w/ very free flowing exhuast ($?). Some intake plentum porting and MAF re-working.

Add-on timing controller. Add-on Air/Fuel controller with larger MAF (like Split Second kit for around $1100). One size larger Injectors ($?).

Raised redline and shift point on ECU to 7500rpm.

Torsen LSD with higher gear ratio may move the shift point enough.

Probably $7k for an extra 100 rwhp.--maybe more hp with the timing controller and some 100 octane.

Bean

iTrader: (1)

i think the supraTT auto's gear is a 3.76 or 3.73

SC300T

Bean,
What is that DEFI HUD you have listed in your mods?