Smashin

You should! It's cheaper to do IS250 than an IS350

An2ny

I just got an FRS LSD I will install it soon…
turbo den- Can you confirm that it is a bolt on swap. Any tips or suggestions while doing the swap?

An2ny

Any updates?
I just got very low miles FRS LDS. I also have a Supra MKIII diff but I will try this FRS one first.
However I have to swap the 4.1 Final Drive gear from the FRS for the stock 3.73.

oo7is25o

Why not just leave the 4.10 final drive? You might as well get the performance boost from having more gear as well as the ease of installation. IMO, By swapping out the ring and pinion from your old case and installing it on your new LSD, you might get into trouble setting back lash and getting the gears to mesh nice again.

An2ny

Yes, you are right; it is going to be a pain to set it up correctly.
I was planning on doing a light prep for SCCA AutoX STX class, so I need to keep the stock gearing, also it will lower 2nd gear top speed by a few MPH and that is not really helpful for Autox.
I may install it with the 4.1 first to see how it feels

oo7is25o

It is stock gearing... Stock for an FRS !!

anyway, isn't stock gearing 3.90 for an 6 spd?

Jeff Lange

iTrader: (1)

Stock for 6MT is 3.73:1 in North America, 6AT is 3.91:1 in North America.

Other countries use some other gearing (namely 3.54:1 for the 6MT in some overseas markets).

Jeff

An2ny

Yes, my car is a 6 speed USA market so it has 3.73:1. I didn’t even know that the manual cars had a different gear ratio in other countries.

Jeff- I was having a really hard time trying to find relevant information about this car, luckily I have found a lot of your posts with great information. Thanks!

FMJ IS

very interested in this mod, anybody can tell what kind of RPM am i at 60/70/80mph with the 4.1:1 FRS final drive?

and how much fuel am i expecting to use more? by %

FMJ IS

also, what about leaving the pumpkin alone and add an aftermarket LSD? any direct bolt on application?

An2ny

According to my calculations I may lose 2.5 MPG if I go to the 4.1, and in 6-gear @ 60 MPH the RPM may increase about 200 RPM, but maybe someone can chime in with actual data.

RPM and mileage impact depends on your original final drive and each gear ratio (manual/ auto/ non USA market) & tire wheel package diameter, if you have the 255/40-18 rear wheels your diameter is about 26” so you can calculate the speed and RPM.

Yes, there are other aftermarket LSD options, but usually they just sell the actual LSD and you will have to install it in a case, also they are a lot more money.

WylieKylie

iTrader: (2)

I've been in contact with Autotech, they are out of stock on the Quaife. Unless there is another source the Quaife is no longer an option.

scott1256c

tom's and quaife have been out for months. Neither is making any more

Gville350

iTrader: (10)

Yeah, I'd not be surprised. When I spoke with them a couple of years ago they only had 5 in stock. I never had the $966 to spare though! Grrrrr! I loved the Quaife LSD I used in my boosted Civic.

Thumper28

iTrader: (1)

I'm not sure if this has already been asked but is the entire diff case from the FRS compatible with the is250 or do you have to install the LSD gearset into the IS250 housing?