First of January, I completed my 2IS 4.08 differential swap on my 2021 IS350, truth is I don't know if I like it.
To clarify before I get into the draggy numbers, I have ****ty tires.
Daily drivability the 2is diff feels the same as my 3is diff (I don't have the dhp so I have an open differential, 3.1 gearing) there is no apparent difference until you punch it.
During the first week of the installation you and the car have to get used to the new ratios, there will be harsh shifts at first but eventually the car will drive as smooth as it beforehand.
Part of the reason of creating this thread is because I don't see an improvement in performance, for years the lexus community has discussed that the 3is is slower in comparison to the 2is because of the gearing with many people wanting to swap the differential, there are only two recorded swaps but none of them have gone in detail comparing numbers. I took the risk and swapped it.
Here are my draggy numbers:

STOCK 3IS DIFF:
0-60:

https://ibb.co/H2xN3JX

1/8th Mile:

https://ibb.co/9HVV2dV

1/4th Mile:

https://ibb.co/C0VFH0G




AFTER DIFF SWAP
0-60:

https://ibb.co/yX28ygt

1/8th Mile:

https://ibb.co/KwpYWJm

1/4th mile:

(I still haven't been able to do a quarter-mile run with the new differential)

So there are the times, I feel like the times stayed the same or maybe got worse. In theory shouldn't I be running faster times? Thoughts?

 

I will post a video later where I go in-depth on the install and performance, I'll make sure to link it to the thread.

 

Don’t think you posted what you intended. All the 1/4 mile images are the same (before and after). No 0-60 or 1/8 mile data for the ‘after swap’.

 

Thankyou for calling that out lol, my apologies, I fixed all the images.

 

Just fixed it

 

I'll never be able to understand why guys who want a faster car refuse to put money into mods that will ACTUALLY make them faster...

If you were already traction limited due to ****ty tires, did you really think a more aggressive diff was going to magically solve that?

You don't need tuning, you just need better and wider tires. Get some lightweight wheels and sticky tires and you'll never see a 6 second 0-60 ever again.

 

Cus my new tires have been sitting in the garage and I haven't had time to install them, but besides that, there definitely needs some tuning to be done, the top speed has been hurt because of the new ratios and the transmission isn't tuned for these specific ratios, I also have to shift 3 times before hitting 60, with tuning I can most likely get it down to two upshifts.

Also, I didn't expect the differential to fix my traction, I never stated that, I installed this differential due to the very long gearing in the new IS350's.

 

Yes, you swapped diffs so the top speed has been reduced. This is reduced permanently, there's nothing you can "tune" on a mechanical differential, unless its messing with the speed governor, but even then, the top speed is mechanically limited now.

Increasing the redline can only be done so much and will only increase top speed by a couple mph.

I would suggest putting your testing on hold until you install your tires, for safety and because you will never get truly faster until you put them on. adding more power will only make your problems worse.