lucas112

So I have a 2016 is350 f sport RWD. I love the car but I want it to have more power. I'm not a big fan of the RCF and oh how I wish there was a 3IS ISF available. Until then... I'll stick with what I have.

Im mulling over the thought of doing a big build; coilovers, sway bars, wheels, tires, and.... the rr racing supercharger which needs to come out asap! All of this would make my IS awesome, but I don't have an LSD to hold the added power and grip. I've been combing through threads on here for a while now and cannot find the answers I'm looking for.

Will the ISF rear differential assembly work on my car? I've read conflicting answers on this. I guess I could use a technical answer. It seems OS Giken has an option, but I really like the Torsen assembly better due to the OEM reliability and I feel like it fits my application better. This will be a daily driver, everyday, fun car that will rarely, if ever, see the track. Please don't give me reasons why I should not do this or tell me I'm wasting money. Technical answers are what I'm looking for. Spending money on a supercharger kit will really depend on if an LSD is a real option I can have.

I have read that the rc350 has an optional LSD. Would this be a better option over the ISF pumpkin?

Thanks in advance for the help.

jkonquer

I started this thread while back

https://www.clublexus.com/forums/is-...rom-rc350.html

So it just comes down to $.
RC350 and RCF currently has a Torsen LSD option, but you are looking at around $2000 for the parts alone. I believe OS Gaiken also makes one for ISF, the RCF and 3IS should come anytime soon. Theoretically, these parts should swap out without an issue.

lucas112

Are they direct replacements? I know the RCF and ISF have different gearing.

jkonquer

Not sure but there is a guy here on forum, lexsense, running 2IS rear diff gearing on his 3IS. Only down side he has was the automatic shifting at weird points.

lucas112

So are we saying the pumpkin is a direct fit? Would the change in gearing be very noticeable?

LexSense

iTrader: (2)

I'm not sure about the RCF or RC350 Differential fitting the 3is.

2is is350 with 4.083 final drive differential should fit. I'm not entirely sure how my shop got the whole pumpkin to fit, but it does fit.
I know the ISF peeps have swapped in a 2is is350 4.083 final drive pumpkin into their ISF which fits and bolts on if I remember correctly.

So in theory with that logic, ISF differential should fit the 3is as well, but I can't confirm that info.

lucas112

Interesting. You don't have any problems with the shift points? The trans will be fine in automatic? Shorter gears would be great but I don't think I can find an lsd with a tighter ratio. Isf and rcf have taller gearing and I would imagine the rc350 lsd would be the same gearing as is350