Like the others before me, I've successfully installed an IS300 LSD on my IS250. I purchased the MT version so the gearing is not ideal like the AT version. But still a big upgrade from the open diff.
I wanted to start by saying that this installation was a little challenging and I learned a couple of things along the way. I wanted to share some tips with anyone who will attempt this in the future to hopefully save time and energy.
Thanks to Jeff Lange and B16da9 for their posts and especially to B16da9 for his advice and help through PMs.
I used a jack and stands to raise the rear of the car up about 24 inches or so. With the method that Jeff did, by simply dropping the diff and then raising it up, will only work if you have the *** end of the car high enough or the car is on a lift. You need clearance to be able to reinstall the side shafts.
I didn't have the car raised up high enough so with the differential on the jack, there wasn't enough room to install the shafts. The reason I could remove it easily was because after the shafts were loosened and the jack was all the way down, you can move the jack from underneath the differential and the shafts separate completely. Trying to reinstall it on the ground then muscling the differential up to the jack was difficult. It would have been easier with a friend for the installation. In the process, I tore a brand new side shaft seal trying to get the shafts aligned and the diff onto the jack.
At this point, I had to jack up the diff and secure it. Then, I removed the brake hub/shaft assembly to get the shafts into the diff. I wanted to avoid taking apart the suspension but I didn't have much of a choice.
Total it took me about 6 hours to remove and install but should have been done in about 2-3 hours. Not hard at all...just a learning process on my end.
Here's a pic of both differentials side by side. The one on the left is the new torsen LSD:
Differential cover with red high temp RTV silicone to seal it:
Internal pic of the IS300 LSD:
I love the traction you get with the LSD and 2 wheel burn outs are awesome!
I highly recommend this performance upgrade.