Also is the gs300, sc400 3.92 the same part number?

 

yeah on my car, when it's 80mph, it's about 3k rpm. the nice thing is, i only hear my exhaust inside the car when it's about 2k rpm. so now with the slightly higher rpm, my car actaully gets a lot quieter when i am on the freeway

 

Finally got it done today.......would like to thank Ray and Sajee at KAAZ USA for the install. For more info on KAAZ LSDs go to www.kaazusa.com.

Well its confirmed that the SC400 pumpkin with 3.92 gears is a direct bolt on for the GS400. No issues with swap whatsoever. These should be easy to find at junkyards for all of you still wanting to do this.

Dropped off the old pumpkin with open differential at home after the install and went for a quick spin. Lets just say the heavy 20s in back no longer exist and that I will be tire shopping on a regular basis. Also will be buying a Valentine One and looking for a BBK. First stop light on a very open straight away was amazing. Left VSC off like I always do and the tires basically lit up with a very hard launch. No torque braking at all and the launch was significant.

Haven't had a chance to go on the freeway yet but got it up to 60 and mid range pull was very nice. The best part of the clutch-type LSD was cornering.....you can definitely feel the inside wheel gripping the road as you make a turn......this obviously never happened with the open differential (or peg leg ). I didnt want to push the throttle too much in the corners until I get used to it. More comments to come on cornering.

My initial thoughts on the gear change is that if you dont care about top-end speed and you are rolling on heavy 20s, go for it. I know its early in my testing, but I honestly don't see why you couldn't go all the way up to 4.27 gears if you are running a large wheel. With the 3.92 thus far, drivability has not suffered at all and I noticed no difference in terms of cruising or daily driving besides a slightly higher RPM. I think that most people who are complaining about traction issues are running a smaller wheel and therefore are not getting the traction that a wider, heavier wheel provides.

UPDATE: Freeway speed of 80mph had a RPM level at 3000. Regarding cornering, I can now get my car completely sideways as the inner wheel grips significantly hard when giving it more than the normal amount of gas........it is so much fun!! Get rid of that peg leg!!! Also with a clutch-type LSD, you must leave VSC off.

After doing research on LSDs, I chose to go with a clutch-type for various reasons. One major factor is I liked the ability to adjust the locking percentage on the clutch-type LSD in order to suit ones driving needs. The overall feedback that I got from many people is that for the type of driving that I do on a daily basis, clutch-type LSDs are superior to Torsen. There are pros and cons for each and depending on how far you drive each day should be a factor in your decision.

Some of the info I came across during my reserach is posted below:

http://overboost.com/story.asp?id=1340

http://www.magnusmotorsports.com/art...azvstorsen.htm

Gear ratios expanded with Supra axle codes and Pros/Cons of Clutch-Type LSDs vs Torsen:

Lexus:

95-97 LS400 has a 3.62 gear ratio.

98+ LS400s have a 3.26 ratio.

92-97 SC300
6 cyl, AT (4.27 ratio)
6 cyl, MT (4.08 ratio)

98-00 SC300
6 cyl, AT (4.27 ratio)

92-96 SC400
8 cyl (3.92 ratio)

97-00 SC400
8 cyl (3.266 ratio)

92-96 MKIV Supra

w/o turbo; (4.27 ratio) Limited Slip
w/o turbo; (4.27 ratio)
w/turbo, MT (3.133 ratio) Limited Slip
w/turbo, AT (3.769 ratio) Limited Slip

97-98 MKIV Supra
w/o turbo; (4.08 ratio) Limited Slip
w/o turbo; (4.08 ratio)
w/turbo, MT (3.133 ratio) Limited Slip
w/turbo, AT (3.769 ratio)
w/turbo, AT (3.769 ratio) Limited Slip

Supra Axle Codes denote gearset family, diff ratio and open or LSD centre.

A01A - 3.916 ratio Open Centre
A01B - 3.916 ratio Torsen LSD
A02A - 4.083 ratio Open Centre
A02B - 4.083 ratio Torsen LSD

Torsen-type (helical gear) LSD advantages:

+ Responds to slippage almost immediately.
+ Won't contribute to understeer.
+ Won't lower your gas mileage.
+ Won't require periodic rebuilds.
+ Requires only hypoid gear oil.

Torsen-type (helical gear) LSD disadvantages:

- Weak compared to the nearly-indestructible clutch-type LSD.
- Slip-restraint action is more jarring than the clutch-type LSD.
- Nonadjustable.

Torsen-type (helical gear) LSD is particularly suited for:

= A relatively stock power output (no more than 133% of stock).
= A car that is driven with a wide range of aggressiveness, with no particular bias within the range from no-aggression cruising to sporty mountain running to all-out road racing - a Torsen-type diff doesn't resist differentiation in the absence of actual slip, hence doesn't provoke understeer in high-grip condition nor provoke oversteer in low-grip conditions.
= A car that is also used as a high-mileage commuter - a Torsen-type diff doesn't contribute to increased fuel consumption.

Clutch-type LSD advantages:

+ Almost indestructible.
+ Smooth slip-limiting action.
+ Adjustable by competent mechanics.
+ Available in high bias percentages.

Clutch-type LSD disadvantages:

- In high bias percentages, can manifest understeer in grippy conditions while manifesting oversteer in slippery conditions.
- Lowers overall fuel economy.
- Requires clutch-plate set replacements as they wear.
- Requires friction modifiers in the gear oil.

Clutch-type LSD is particularly suited for:

= A power output modified significantly (over 133%) beyond stock, but still putting power through the stock-dimensioned diff case - the clutch-type can handle a huge load and lots of abuse, which is important if you're completely exceeding the OEM design parameters.
= A car that is primarily driven at all-out race pace - the understeer issue don't apply since a race-driven RWD car should always be on the verge of oversteer.
= Not a high mileage commuter - that is, unless gas is cheap and you're into rebuilding diffs.

"Car manufacturers don't equip even super-performance stock cars with clutch-type diffs because with full engineering and fabrication control, they don't have to tolerate any of the disadvantages of the clutch-type diff. For whatever high level of power, a manufacturer would just use a bigger diff case to hold a higher-torque-capacity Torsen-type LSD. Note that neither the MKIV Supra, e36 Euro M3, nor e46 M4 came with a clutch-type diff. The Supra and e36 M3 both came with Torsen-type diffs. The e46 uses an advanced but oddball diff, in case you were wondering.

The only case I can imagine a party with full engineering and fabrication capabilites (a professional racing team) resorting to a clutch-type LSD is in racing, where a smaller clutch-type LSD can do the job of a bigger and heavier Torsen-type LSD, nevermind the drawbacks.

But in the absence of engineering and fabrication capabilities, clutch-type diffs are a godsend for amateur racers with dedicated race cars."

Hope this info helps........on to the next project.......custom shorty headers!

 

give you credit for going for it now take it to the track and see what kind on 1/4 mile times she produces...........

 

slowdriver - where in california are you located? Id love to take a test ride if you're local.

 

Slowdriver,

All said and done, how much did this mod cost you? I'm also looking at my options for LSD now, and you've given me one more to think about....

 

Nice write-up, I thought the 3.92 gears would put you at a higher RPM at 80mph. My 3.76 is at 3K as well at those speeds. Maybe I need to upgarde

 

slowdiver is rolling on 20s which typically (depending on tire size) are about 1" larger diameter than stock diameter. This would offset the lower 3.92 gears compared to 3.76 with stock diameter tires. I am turning right at 3k rpm at 80 mph too, but my 18s are very close to stock diameter (but not width )
Sounds like the 3.92 gears are a good way to go especially for those with big, heavy 20s!

 

seriously if i didn't get a super good deal on my current 3.76, 3.92 was what i was looking for already. people with 18s and 19s they all get 3.76, i have 20s, i should get something else

 

Gotta pay attention to those sigs....

 

I forgot I had a 3.92 diff sitting in the garage.

Hmmmm..

It's got approximately 50K miles on it.

Sell?

 

go all the way to 4.27 bro......seriously if you do not care about top end speed then go for it!!

you can even buy the 4.27 gears brand new at your local dealership.

 

What would the top speed be capped at with the 4.27 gears?

 

65.



j/k

Let's see, if 3.23 -> 3.76 (.43) goes from what, 149 to 135 (-14)?
Then 3.23 -> 4.27 (1.04) would go from um 149 to 149 -14*1.04/.43 or 115

No idea if that's right.

 

Oh and slowdiver - but congrats on the custom upgrade!

You'll find you won't really need to turn VSC off though I don't believe.