Tochigi-Fuji Super LSD vs Torsen LSD - Miata Turbo Forum - Boost cars, acquire cats.

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Old 10-28-2009, 04:26 PM   #1
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Default Tochigi-Fuji Super LSD vs Torsen LSD

I've been talking to a member about swapping my Torsen T1 4.10 for his Tochigi-Fuji 3.9 out of a 2002 SE.

Here is my question:
My car is a street driven car. No track. If I ever do anything track related it will be at the drag strip. The torsens are known to really dislike being launched. Is the Tochigi-Fuji better for my needs?

Reading up a little about the two on m.net "garage" section, but your opinions/feedback is more important to me. Torsen is a gear "type". Tochigi is a clutch type? I know the rx7 tII clutch type rear ends are best for drag racing/launching, but what about the Tochigi-Fuji?

Is it worth the time/effort to swap it? The fd is a little lower and that I like. But its characteristics for my planned use????

Any input is appreciated.
TIA
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Old 10-28-2009, 04:36 PM   #2
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A couple posted problems but I'm not sure if that's a big enough sample to make a conclusion.

shuchi-fuji vs torsen - MX-5 Miata Forum
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Old 10-28-2009, 05:22 PM   #3
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3.9 is far too tall for strip use. Run your car in the quarter mile and see what mph you have. If the car does not hook on what you have, it will still give you a pretty accurate mph.

Ideally, you want the rpm to be just past the rpm that you reach peak horsepower at the trap. You do not want to be on the limiter before the finish line, obviously. However, most street strip cars go taller for driving comfort and more horsepower potential down the road. There is a formula that figures out how fast your car will go in the 1:1 transmission gear ratio.

I run a 4.44 and 22" tall tire, and it is still way too tall. Theoretically it will go 118mph at 8000 rpm (my shift point). At 7200 rpm, you would top out at 106mph with the same size tire. Probably too low for you. 4:10 or 4:30 would be better. Don't forget, you can go with a taller tire, if you start to top out too soon.
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Old 10-28-2009, 05:28 PM   #4
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02 is a TorsenII. 03 is is T-F LSD. 03 was the only year of 3.9 T-F LSD.

I wouldn't run an 03 3.90 T-F LSD. Of all the blown up torsens I've run across, probably half of them are 03 3.90's. Many of them were set up incorrectly at the factory.

Last edited by Ben; 10-28-2009 at 06:00 PM.
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Old 10-28-2009, 05:40 PM   #5
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Quote:
Originally Posted by Ben View Post
I wouldn't run an 02 3.90 T-F LSD.

Of all the blown up torsens I've run across, probably half of them are 02 3.90's. Many of them were set up incorrectly at the factory.
This was my concern after buying this piece. I was originally looking for it since a 3.90 final drive ratio is EXACTLY what I wanted for my driving style. I'm used to sport bikes with tall gears...and I commute 150miles daily to get to and from school.

While I like the idea of the cone clutch, preloaded diff...I can't justify installing it and having it blow up later.


Most of the failures I've heard of were at low mileage (30-40K)...so I assumed if they made it past this they were golden.

Any and all elaboration on the failures you've seen would be appreciated.


EDIT: BTW...this one is an '03 unit. I doubt it makes a difference...just clarifying.
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Old 10-28-2009, 05:57 PM   #6
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I went back and looked.. I meant 03 diffs as having issues, not 02. Original post edited.
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Old 10-30-2009, 05:21 AM   #7
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Street driven turbo cars feel much better with lower gears. I had a five speed and a 4.1... always wanted more gear in first and second. (225/45/15 NT-01 on the street)
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Old 10-30-2009, 08:54 AM   #8
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Quote:
Originally Posted by Nagase View Post
Street driven turbo cars feel much better with lower gears. I had a five speed and a 4.1... always wanted more gear in first and second. (225/45/15 NT-01 on the street)
When you say lower, do you mean lower number and taller gear?

Lower gears, usually means higher a numerical and lower gear ratio. 4.88 is low and 3.90 is high.
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Old 10-30-2009, 09:04 AM   #9
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He means lower = longer gears
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Old 01-10-2010, 08:45 AM   #10
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Bump on this.

I'm going to finally install this diff when I slap in the replacement 1.6L from hustlerbunny.

I'm considering building a 1.6L since I'll be able to take my time without the car being down...and really wonder if this diff will stand up to the abuse.

Am I going to be the first one to find out...or is there anyone out there we know of making 250+whp on the '03 LSD?

I just need to install and enjoy...but I've got hustleritis.
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Old 01-10-2010, 03:09 PM   #11
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The rx7 clutch type has held up well to all the abuse I've put it through in the past couple years. 300hp, drag racing, tracking, daily street driving, mega burnouts ect.

And its cheap!
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Old 01-10-2010, 03:12 PM   #12
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its not the same as teh TF tho
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Old 01-10-2010, 10:14 PM   #13
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Quote:
Originally Posted by 18psi View Post
its not the same as teh TF tho
This.

I wish it was...and missed out on a lot of RX7 setups.

Supposedly the TF is great...when it works. I'm just trying to determine if more power increases their propensity to grenade.

All the failures I've seen were in the 20-40K mile range...so I'm presuming that if that last longer than that they were properly constructed and will have a normal life.
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