I know this topic has been discussed before but doesnt seem to be a lot of answers.

Are there other compatible rear diffs for ours cars? I guess there is no such thing as a gear swap like with a mustang lol.

I know the is350 diff is a direct swap with the 4.09 gear but ive also read the gs430 uses the same diff as the is350, so shouldnt that swap into the isf as well?

The 06 gs430 had a 3.77 gear which might be a nice in between from the 2.94 to the 4.09 of the is350.

Did the gs430s have LSD option at all?

 

 

^^^
so many pics, search function, yada...

There are already too many gears.

To op: find and completely read long thread on the 4.09 gear in the isf. 130 mph top speed and no quicker et. (spoiler alert)

 

I just find it weird that we have 8 gears but only use 4 of them in a 1/4 mile, most 6 speeds will finish the 1/4 in 4th gear as well, usually the 1.0 ratio gear. Whats the point if having 8 gears over 6 if you arent taking advantage of them?

With the 4.09s we would use 6 gears and finish in 6th, the 1.0 ratio gear.

I dont see how it could possibly make the car slower and im pretty sure the fastest 1/4 mile NA ISF is running the 4.09 rear gear and ran 11.7 in the 1/4 so I refuse to believe the car isnt going to accelerate quicker to 130 mph.

Im guessing a tune could remove the top speed limiter and the 130 mph top speed although thats really not a huge deal to me as im not one to exceed 130 mph pretty much ever.

 

7th and 8th are basically just overdrives, the car will reach top speed in 6th gear

 

Simple math. Area under the curve. You're kidding yourself if you look at the thread from the people who actually did this.

 

Ive read a few threads on the topic, didnt see anyone claiming it made them slower? Seemed like they all said it made the car feel more alive, one said it felt faster all around from every speed.

Simple math says a 4.09 rear diff is going to multiply engine torque to the ground at a higher rate and accelerate the car more quickly.

Thats why swapping rear end gears in domestic cars has always been such a hot item for the mustang, camaro, corvette guys, swap from a 2.73 to 3.73 rear end and run 1/2 second quicker in the 1/4 mile for a few hundred bucks.

What math are you using that says a car with a 4.0 rear gear accelerates slower than one with a 3.0 rear gear given all other variables the same and assuming traction isnt a problem.

 

So should we all look into getting some custom 1.93 gears made to swap out these garbage 2.93s?

 

The greater issue is the shift point maps in the TCU are fixed/programmed for the 2.94:1 ratio. So tossing in a foreign gear jacks with all the TCU parameters.
Taking it step further the ECM is not seeing the typical load it expects so again, the drop in isn't complete and functional like a 1992 Mustang/Camaro.

 

We have too many ratios in the gearbox. I am attaching a great article on horsepower and torque to illustrate my point, however you will likely read it and tell me it makes your point for you and tell me I'm looking through the wrong end of the telescope. Pay close attention to this paragraph:While the car will feel better in first gear, that's all you'll get. Nothing after you get to the meat of the powerband will matter unless you fall out of the powerband for some reason.

 

Good read, then what do you make of these simulation results?

I think the article in there kind agrees with me, they added a higher gear in "ricer" and it accelerated a lot quicker and closer to "redneck" lol

Whys math say stock gears will do this 0-60 mph:4.23
0-100 mph:10.40
60 ft:2.04@38.18
330 ft:5.34@70.79
1/8 mile:8.12@88.79(90.35 actual)
1000 ft:10.53@101.79
1/4 mile:12.58@109.65(110.45 actual)
Max Accel:0.955 G
Air Density:0.00231552 slug ft^3
Time Delta:10.0 ms


only change in the simulation is the gear ratio from 2.93 to 4.09,

0-60 mph:3.82
0-100 mph:9.78
60 ft:1.80@38.66
330 ft:5.02@72.00
1/8 mile:7.76@88.76(90.29 actual)
1000 ft:10.16@102.69
1/4 mile:12.21@109.55(110.34 actual)
Max Accel:1.246 G
Air Density:0.00231552 slug ft^3
Time Delta:10.0 ms

I think we are just looking at things differently. Obviously a gear change isnt going to make the engine more powerful and increase trap speed, it just increases acceleration, basically all of the advantage would be from 0-60 mph, but I still think it would make the car feel more lively and would always be in the meat of the powerband with those gears, allowing the 4.09 gear to get a jump on a 2.93 geared car in a roll race but thats my thoughts on the matter.

identical ISF, one with 4.09 gear, one with 2.93, the one with 4.09 gear should get down the 1/4 mile a good margin quicker assuming traction isnt an issue, thats all im saying here