LexSense

iTrader: (2)

Hey all, just wanted to let you guys know that I've purchased a used 2nd gen is350 differential pumpkin.

The plan is to swap the internal ring and pinion gear over to the newer 3rd gen IS350 pumpkin.
Since it was mentioned by r0shiro that the housing isn't a direct swap, I figured I'd pull the trigger and go a different route with the install.

Now as far I know, I'll be the first guinea pig with this install? There's no guarantee that the 2nd gen is350 ring and pinion gear will even fit the 3rd gen's housing. Though the specs sheet show both the ring gear at 208mm (8.19 inches).

Concerns:

1. First and most obvious is will the ring and pinion gear fit?
2. Top speed seems like it will be RPM limited to 110 -115 mph in 6th and 7th and 8th gear
   (according to research from the ISF to IS350 differential housing swap where speed was limited to 130 mph). Hopefully a speed limiter removal will be possible in the future.
3. Gas mileage would probably tank - but I'm not too concerned with that
4. Shift logic from the ecu/pcm can get wonky with the new shorter rear end gear.

I've had the differential shipped to the shop where it will be installed this Friday, and will keep you guys posted with the results.

Any tips/advice?

Does anyone want to talk me out of this project LOL?

Jlin89

I've been thinking about the same. Since the 2016 RC is coming out with LSD I'm just going to wait for that instead.

Other than quicker acceleration with the 2is gearing, it doesn't have any other benefit.

AMNss

Interesting...

A few months ago I was discussing the same thing with a 2is owner. Anyway don't forget posting the 0-60 mph times

LexSense

iTrader: (2)

I think to minimize risk I'll have them pull the diff cover off both the differentials and then see if the ring gear is at least physically the same diameter and thickness wise.

This way I'm only out some diff fluid and not the whole arm and leg I'm paying for labor.

Diameter of the ring gear should be confirmed, thickness however, is still up in the air.

E46CT

Looking at the pics of the 2IS diff (4.083) and the 3IS 3.15 (i forget--is it a 3.15?) the diffs seem to have similar mounting points on the ears and the front. I was wondering if the 2IS 350 4.083 unit would bolt up to a 2IS. That would provide a pretty good difference in standing start acceleration.

brendanf

if you search for it, there is a thread from a guy who used a diff out of a BRZ /FRS. it bolted right in and was an LSD. the ratio was only slightly different

E46CT

Interesting. A bit expensive probably but still interesting. The ratio would have to be drastically different for me to consider. don't really care about LSD. The FRS auto is probably geared more aggressively. Is LSD standard on that car? a non-LSD from an automatic FRS (if there is a non-LSD) would be interesting. Or an LSD from an automatic if its not too expensive.

jkonquer

I would love to get a lsd with a taller final gear. These 8 speeds are way too long to have fun without going to jail.

brendanf

Well my advice then would be to start digging around the local wrecking yards for a diff from a BRZ/FRS and swap it in..

You can check www.car-part.com . It allows you to search all the scrap yards all over North America for whatever your looking for.

redspencer

iTrader: (1)

Just to clarify, the FRS/BRZ Torsen LSD is only compatible with the 3IS250/2IS250.

LexSense

iTrader: (2)

4.083 left. Stock 3.13 right
Updating in case this helps anyone in the future, and since I'm going back to mostly stock.
In order to get the 4.083 diff in from the 2IS you'd just need to swap the diff covers to get it into the 3IS RWD.
Sorry if formatting is off posting from phone

eicca

Am I understanding this right, you just swap the rear plates? The mount points and driveshaft attachment are the same?

I would love to get a 3IS 8-speed and put the 4.08 in it. That thing would be a monster. Sexier than the 2IS for sure and doesn't burn oil.

Lex3is16

How different does the car feel I have been searching for this exact thing because I got gapped by 2is lol

GISguy

So what happened with this? Sorry to bump.
Did it fit, and how did it affect your 0-60?