Sci

Hi folks

Can anyone confirm whether the 3.266 gears from either the 1996+ JDM JZA80 or -2005 SC430 are a bolt-in swap in the ISF diff centre?

Note this is not the "big" Supra B diff but the smaller A type.

Not interested in swapping the whole pumpkin because finding a reasonably-priced Supra LSD one in the correct ratio is next to impossible, also not interested in just getting an open diff pumpkin because i want to keep the Torsen centre my car came with!

Im pretty sure the 3.133 gears from the LS460 *will* fit, as the part number for the diff centre is the same as for the ISF open diff, but i want to go slightly shorter in ratio than that, hence the 3.266.

And yes i have searched! But no one seems to have a definitive answer....

MK4Sup_isF

iTrader: (10)

why not just get the IS350 carrier. easy swap

Sci

because 4.08:1 is way too short a ratio for a daily driver ( i read that thread and note that of the two people who tried it, both ended up going back to stock ratios)

Jowett

The GS450H uses a 3.266 rear end, my guess is this would be the one you need, but it is speculation at this point.

R&P# 41201-39717

Swacer

Oh absolutely. That is way too tall of a gear for a daily driver, and even worse for an automatic. 4.10s are usually best in a stick car and are only good for the weekend driver and the person who takes the car to the drag strip often. Also, with a ratio that high, you are going to zip through gears 1-3 almost instantly.

Compthis

iTrader: (1)

I was one of them.....if I could have a switch to turn the 350 diff on and off I would but for every time I drive I had to go back. It was too much

darbs242

iTrader: (5)

I was the other and it's a mistake. Feels likes a hot rod not a lux sedan. I agree and have been thinking about doing the gs450h gear but only if it can be equipped with a limited slip

Sci

Yes that is the part # I had too, the original # that shows up for the Supra/Sc430 (41201-19645) has apparently been superseded by this one so they must all use the same set of gears


My thinking is that if any other Lexus/Toyota's running different rear end ratios used the same diff centres as the IS F (either the open or the Torsen) then their crown and pinion must surely fit the IS F too

There are a bunch of different Lexus that used the same open diff centre as the IS F, but they only used the 3.133 gears not the 3.266. For some reason the 3.266 cars centres are different part # which still leaves a bit of a question mark over whether they are compatible

RSXiMUS

iTrader: (7)

I'm very tempted to try this...

My friend has a great shop that can swap it out for me.

I know when Honda switched from the 4.389 FD in the 02-04 RSX-S to 4.764 in the 05-06 RSX-S it made a HUGE difference.

Jowett

Perhaps one center section has the preload spring lsd "light", and the other is a plain open center section? Compare all the carrier and pinion bearing part numbers, the drive flange, shims, etc. If those parts are the same, there is a good chance things will swap.

Sci

Good idea, i compared the bearing numbers and even the crown wheel bolts and the good news is they all match up

i have pricing for both the 3.133 and 3.266 final drive gear kits, so i guess the only thing left to do is decide which ratio to go for and pull the trigger...

Yep, ive swapped diffs in Toyotas and Lexus before (eg SC400 going from 3.9x to 4.08) and know what a difference it makes. Usually cars are slightly overgeared from the factory for economy and it seems with 8 gears the IS F is a prime candidate for a shorter ratio diff. In my experience as long as you dont go crazy with the ratio there is basically no difference in practice to fuel economy or top speed

I will pull the diff myself but will need to take it to a shop to have the new gears installed and set up

RSXiMUS

iTrader: (7)

Nice! Okay I am going to pull the trigger on the 3.266 kit, found it online for $660. This should be nice to bump my RPMs up a bit in 8th to get out of the drone zone.

As far as shims go ect. any other parts I need to complete this swap that you recommend Sci?

Sci

Yep that is about the same price as ive found for the kit direct from Japan (im in Australia)

You cant really get shims with the kit because you wont know what thickness until the gears are in and set. The shop i will be taking mine to deal with a lot of Toyota diffs and transmissions so they will know what to order should anything extra be required but i cant imagine any place that does differentials would have much trouble.

Since my car is fairly low mileage i'll let them determine whether any bearings, etc need to be replaced.

I'll probably need to allow a week for the car to be off the road while this gets done so even though i can order the kit right away it might be a couple of months before i have time off to do this

Sci

dont know if this link will work but here is a spreadsheet i did up with various info about differnt ratio Toyota/Lexus diffs

https://dl.dropboxusercontent.com/u/...ar/ratios.xlsx

as a guide, at 100km/h (~60mph) in 8th the stock diff will have the engine at about 1600rpm, with a 3.133 it will be at 1700rpm, with a 3.266 it will be at 1800rpm

that doesnt sound like much on paper but it will definitely be noticeable

Compthis

iTrader: (1)

Before anybody wastes time and money, I want to remind you our tranny is a true auto not manual. The tranny has computers that tell it to shift up or down and it will shift down automatically in manual when slowing down. What I'm getting at is when I had the 350 diff in, the tranny acts like it had a mind of its own. I think the program of the computer it closely tied to the tranny, RPM of the engine and gearing of our diff. Change the gearing and your car will not respond normally. Some issues you will experience is the car will hold gears when in automatic going up and down. You will watch the rpms climb while driving normally but the car won't shift into the next gear. Slowing down will have issues too. The gears won't gear down normally when slowing but rather do whatever it wants by either holding the gear and just going from lets say 5th to 1st. I think you're making a mistake but it's your money your time, good luck.