Downshift

The weight is how you check. A LSD one will be 95ish lbs and the open ones are only 55 I think. I'm regretting not getting an open on and saving some cash to swap to a clutch pack style LSD.

Stock gearing is barely a tick over 2000rpm at 50mph too :D

I went with 4.88s in my automatic FRS. Absolutely love it. Lots better acceleration and I can still get over 30 mpg at 70 mph. Best mod I have done.
60 mph tach's at 2500 rpm
70 mph tach's at 2750 rpm

I only paid $270 for my gear set from
SPENCE WEIR
Weir Performance Engr., LLC
707-315-6638

Thanks for the reply @Lunatic that's a great price.... Did you install your self?

All I know is it's 1900-2000rpm at 50ish mph and witha 9:1 engine it doesn't like to pull down that low in 6th gear lol.

No, I had a local shop install it.

From what I gathered, the gear is the same gear in all 8" v6 toyotas. You can buy the gear sets for $285 shipped from Spence at Weir Performance or a similar set made by Motive Gear for $210 shipped from jaws.

http://www.jawsgear.com/Ring_And_Pin...duct_info.html

Either way you go, you'll likely want the solid spacer Spence sells over the crush spacer. I've "successfully" installed both into my housing (4.56 ratio, can't speak for other ratios). See the DIY below. I say successfully because I ended up redoing the Weir Gears with Motive gears after a ruined them by running them out of alignment. But both fit the housing.

I bought my IS300 carrier from a local shop for $250 and it had a Torsen T2 LSD, same one that's already in the car. They are pretty common, at least around here. Here's how you track down one that is an LSD:

Look for M98/M85 sticker:
http://www.ft86club.com/forums/showthread.php?t=49288

You'll want to look for an IS300 from 2001-2005 (can't remember exactly?). This will also help you find the diff based on the vin sticker (from is300 forum):

"look on the sticker inside the driver door that has the vin number. on the bottom left corner of it it should say like..."a/tm:B##X". if the X after the numbers is b or c, u have lsd. a = no lsd."

http://i289.photobucket.com/albums/l...0-06-55-06.png

There is also a DIY here for doing the swap yourself. It's doable out of an apartment, but difficult. You can find my posts toward the end.

http://www.ft86club.com/forums/showthread.php?t=54054

I wouldn't recommend going over a 4.56 ratio if you DD it above 75 regularly (Edit: This is my recommendation for a manual, it's different for an Automatic). I love the 4.56 swap a lot, even if I basically did it twice to get it right. Noticeably better acceleration and RPM on the highway is just about the max limit I'd be ok with.

The vin # is great if the diff is still in the car. If like most Scrapyard's its on the shelf the weight trick works 99.99% of the time. Also the ring is the same but the pinion is different than the trucks so that's a no go. I also got a quote from weirperformance, $780...... That was gears, bearings and the solid spacer.

Here in Houston they almost never remove the parts from the cars, so that's kinda lucky for me. It can definitely get tricky if they have and there is no sticker on it.

I was able to fit the 4.56 Motive Gear I listed into the IS300 carrier and successfully set it up and run it without any issues. I will say that the pinion depth made the pinion come kinda close to the center of the diff. Probably .020" or so of clearance there. Weir gears didn't even get close.

With bearings, it definitely gets pretty expensive. I saved a little bit of money by just ordering all of the OEM IS300 bearings/seals/nut from toyotaonlineparts.com. I think all total, the project was close $1k in cost.

Jesus, I'll stick to my $700 bolt in deal thanks. 0.020 is a little close for my liking on the pinion to carrier clearance but to each their own.

Keep in mind that that includes a new carrier. So I have an untouched OEM diff in my closet now that I can easily swap back in. I doubt you could find a diff that would fit that already has a 4.56 ratio. I know the IS300 diffs are 3.9 & 3.7, so going lower is an option for just a direct swap with little hassle. But going with a lower ratio kind of defeats the point if you plan to stay NA like me and want a boost to acceleration.

If you use a solid spacer, the spacing there won't be an issue. Everything is very solidly fixed in place at this point. Even with a crush spacer, .020 of movement would lead to a SIGNIFICANT change in gear mesh pattern, and the gears would be ruined.