Limited Slip Differential (LSD)
The FRS/BRZ diff is a Torsen (torque sensing) Diff. Not the greatest but still miles better than an open diff.
As far as gear ratios, the 86 twins uses a 4.1 final drive where the IS uses a 3.7 (iirc). So yes, fuel consumption will increase. However, acceleration will improve with the advantages of a LSD.
Or you can just go with an aftermarket clutch type LSD.
As far as gear ratios, the 86 twins uses a 4.1 final drive where the IS uses a 3.7 (iirc). So yes, fuel consumption will increase. However, acceleration will improve with the advantages of a LSD.
Or you can just go with an aftermarket clutch type LSD.
The FRS/BRZ diff is a Torsen (torque sensing) Diff. Not the greatest but still miles better than an open diff.
As far as gear ratios, the 86 twins uses a 4.1 final drive where the IS uses a 3.7 (iirc). So yes, fuel consumption will increase. However, acceleration will improve with the advantages of a LSD.
Or you can just go with an aftermarket clutch type LSD.
As far as gear ratios, the 86 twins uses a 4.1 final drive where the IS uses a 3.7 (iirc). So yes, fuel consumption will increase. However, acceleration will improve with the advantages of a LSD.
Or you can just go with an aftermarket clutch type LSD.
Id go with an aftermarket clutch type LSD and just keep the same ring and pinion.
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That was me, the frs diff is a direct bolt on, Is250 AWD will benefit the most from this swap because both have same ring gear size and same final drive ratio. You have to be a track star to use this setup because it revs up very fast and keeps you in a more favorable powerband (rpm) at high speeds. For daily driving you will suffer mpg. Ever driven a frs on the freeway? 4K rpm at 70-75 mph.. Same goes for is250 if you swap it in. The cornering grip was awesome though, I felt a big decrease in lateral grip after going back to stock
If you're looking for something factory, the 2010-14 IS F rear differential is the best option for the IS200t. It's a factory Torsen T2 LSD with the same gear ratio as the IS200t (2.937:1).
Jeff
Jeff
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Also, if you know where I can find one at a junk yard or for sale lmk
We've had a couple of IS-F OEM LSDs up for sale on the 2IS/IS-F classifieds a short while back. Try searching there to see if a used unit is still available. Switching from an open differential to a mechanical LSD is well worth it. 
https://www.clublexus.com/forums/2ge...eds-06-13-173/
https://www.clublexus.com/forums/2ge...eds-06-13-173/
Just curious will the ISF OEM LSD fit a 3IS RWD IS250? Also in terms of aftermarket clutch type LSD I saw one from cusco for the frs/brz. I assume for daily drive it'll still increase fuel consumption for the 3IS though.
