Lvangundy

I got the *edit* Supra TT LSD put on today - jeesh, what an expensive mod! The LSD is worth it. The gearing change is slightly noticeable, but the limited slip takes the cake on corners and off the line acceleration.

I ran a G-Tech before I had it installed (even with the new one in the trunk (100lbs extra?). -

Stock 3.23(?) gears (non-LSD)
Temp gauge: 70F
0-60: 6.39

Supra TT/LSD 3.76 gears (LSD)
Temp guage: 66F
0-60: 6.48

HMm. Why was my time better with a higher temperature, and an extra 100lbs in the back? Both times I lost the same amount of traction which wasn't much. A SMALL amount of tire 'screech'. These were 1-runs, not multiple averages.

With the 3.76 gears I notice shifting from 1st to second takes the car a little longer.

LMSguy

I'm going to go with tire spin even though you "think" the spin was about the same.
G techs can be pretty accurate but I'd like to have seen more than one run done.

chuckb

curious for another G-tech time now without the spinning

JBrady

Lee,

Which GTech do you have?

I have the GTech Pro Competition model which is essentially the same as the RR model

http://www.gtechpro.com/rr.html

If you have the original GTech you do not have the ability to check time to any speed (such as 0-55mph).

Using a calculator I have that adjusts vehicle speed to gearing changes and/or tire diameter changes I find the following:

Our fuel cut is at 6350 and our ECU begins backing off power and shifting around 6000rpm. Sometimes higher, sometimes lower. So, using 6200rpm is actually a bit optimistic for shift points but lets look at the data.

Standard GS400 gearing gives 69mph at 6200rpm. This is using 26.63" tire diameter and the stock 3.266 ratio. My LS400 has the exact same stats and I usually see an indicated 67mph at the top of 2nd gear. Now, lets change to 3.769 ratio. Now, the speed in 2nd gear at 6200rpm is 59.8mph. Obviously the car must now make another shift to reach 3rd gear BEFORE it reaches 60mph. Gear changes are SLOW and while the car is actually still accelerating during the shift is slows down considerably due to the ECU reducing power and the slip period as 2nd releases and 3rd engages.

The thing to do would be to compare 0-55mph before and after.

You can also leave manually hold the car in 2nd gear and accelerate to fuel cut which should give you 60mph.

This will give you better comparison data.

Another thing people often miss is that the OLD gears give better GEARING at the top of each gear as compared to the new gears. Let me explain:

Stock gearing gives the following speeds in the following gears at 6100rpm:
1st = 44mph, 2nd = 68mph, 3rd = 104mph, 4th 148mph

3.769 gearing gives the following speeds in the following gears at 6100rpm:
1st = 38mph, 2nd = 59mph, 3rd = 90mph, 4th = 128mph

So, comparing these numbers we see that from 38mph to 44mph the STOCK geared car is still in 1st gear while the 3.769 geared car is in 2nd. This gives the stock geared car much better torque multiplication for this range than the 3.769 car. This also is the case between 59mph and 68mph, 90mph to 104mph and 128mph to 148mph

DaveGS4

iTrader: (2)

Lee how much longer? Did you notice it hitting the rev limiter (kind of like a stuttering feeling?) If that's happening it definitely slows you down.

chuckb

actually, stock GS4 16inch tires are 25.7 inch diameter and stock 17s are 25.3

Faraaz23

Perhaps your slower 0-60 time with the 3.76 gears was due to the fact that (according to the info provided by jbrady) the car is at 59mph at the top of 2nd... you're gonna need an extra shift (hence a couple more tenths of a second or so) to get that extra 1mph clocked on the g-tech. Just a thought.

Lvangundy

Wasn't the rev limiter, it just shifted at a higher point. (longer..)

I have the old g-tech.

I'm going to try again today and see what happens.

La400

Hi,
Read your thread and I have a few weeks ago installed the 3:76 LSD. I have not taken to track no use any other devices to see difference yet. I have run at track before with stock rear end. This I do know that on one road that I test I would normally be doing 60MPH and now at the same point I am doing 70MPH and gaining quick. Also I noticed too that leaving in 2nd performace is much better, passing cars is effortless on highway. MPGs seems to be only effected on highway, combined about the same and just around town, better MPGs. Passengers have stated that from their side it is pulling stronger. Also this have helped me slow my driving down some, which was needed.
Everything that I had read before installing stated that we should get 1/2 second quicker in 1/4 mile, don't know yet. Will be testing for sure.
My trans is shifting better and quicker, utilizing factory 16" wheels.

Thanks for your thread of information.

Lvangundy

Did a couple more runs with and without traction control on.

First run was horrible, the car just wasn't ready to be floored and the transmission was lagging.

#1 (trac on)
7.43 (eek)

#2 (trac on)
6.58

#3 (trac off) eased into the throttle
6.23!

So unless the g-tech is acting up, this has been my best run. We could 'say' that the 3.76 w/ LSD can drop your 0-60 about 2/10ths of a second.

I'm not sure, but I think the car was in third by the time I hit 60. Second gear seemed to go by really fast.

DASHOCKER

iTrader: (2)

Ithink the 3.76 gears are better suited for the gs3 than the gs 4. Correct me if I'm wrong, the gs4 and gs3 have different gear ratios due to the engines? I have a gs400 and I am going to keep the gearing stock. I will use the cash to probably mod something else that woul yeild more horses like a blower

chuckb

good luck getting a blower for $1600 I think the 3.76/LSD combo is best bang for buck on a GS4. I'm hoping to get one in the future

GS3 has higher 3.90 gears stock, but it needs it because it has less torque.

DaveGS4

iTrader: (2)

Shocker, the GS3 comes with an even steeper gear ratio at 3.9x and a 3.76 gear would slow it down more than stock.

TeeLex

iTrader: (24)

While I don't have any track times to verify, there is no doubt that my car is quicker and much more responsive with the Torsen 3.76 LSD. I figure I lose about 1 - 1.5 mpg, but gain 5 smiles per hour!

Lvangundy

I'd recommend anyone wanting to keep things mild, just get the *TRD LSD unit and install it into the differential. It's nearly half the price ($900). The benefit of the TRD Torsen LSD is great for daily driving. A clutch-type might be better desgined for racing (from what I've read online), which I think KAAZ makes.