A70 Circuit Racers - Which Diff?

[Shane001]

Hi Guys,

It appears finding someone who makes a spool center is not going to happen, so I was wondering what diff u guys are using at the track. Specifically dedicated track cars for circuit racing only, not drifting and not drag racing (obviously these would have other ideal requirements).

So as far as I can see the options I have are;
1. CIG Locker (I'm currently running with a 4.11:1 CIG Locker - and yes, this is a welded torsen, and no I didn't do it) :3d_frown:
2. Factory Torsen.
3. Factory clutch LSD (though I'm assuming this is only a 1 way).
4. Kaaz 2 way clutch LSD.
5. TRD 1.5/2 way clutch LSD.

So what are u guys in the US using at the track and why?
I currently have a 3.7:1 clutch LSD that I was thinking of taking it out for a test run, bad idea?

Any and all feedback and advice hugely appreciated :icon_bigg

PS: For anyone who's interested, my car is a dedicated track A70 with a 1JZ with single turbo. I run in a category called Improved Production in OZ. Bought the car last year in July and got a lot of work to do to move this car up the grid

 

[Colie]

It's my third diff, and now i'm running a torsen 4:10 from a turbo R and it's working good.

If i could afford it, i would buy a Kaaz 1.5 way.

Nice supra btw.

 

[Shane001]

It's my third diff, and now i'm running a torsen 4:10 from a turbo R and it's working good.

If i could afford it, i would buy a Kaaz 1.5 way.

Nice supra btw.

Thanks mate, they are a great looking car though aren't they

Your third diff! What have u been using? How have they failed? Any idea how many race laps u would get out of a diff before it failed?

I'd prefer to be running with a spool but for the money it's gonna cost to have a custom spool made up I could by a Kaaz 2 way instead!

 

[prsrcokr]

My vote is for the Torsen (JZA70) but I'm not sure why the 1.5/2 ways are perferred by some folks (adjustable preload?) Remember, any clutch type diff is going to wear and the packs will need to be replaced. The torsen won't wear as it's mechanical.
I can throttle steer like before and hang the rear out like with the stock LSD.

I put together a 3.73 Torsen that I'm using now (seems to be a good track gear). Also have a 4.10 that I picked up, might use it for short tracks if I get serious enough to swap for each race.

 

[Clint]

In my own opinion if it where me id go with the Kaaz 2 way or the 1.5 clutch LSD! The stock JZA70 4:10 diff can only hold so much power to the wheels before they fail. And a 3.73 may have to long of gears for short track racing.

 

[prsrcokr]

The 3.73 isn't bad, it's what I used for half of last seasons auto-x's (which I won the class) As far as the Torsen, people breaking them are launching on slicks, for track stuff you don't launch the car. I'd like to know if anyone has had trouble at high power with one other than drag stuff though.

 

[IJ.]

Shane: Torsen is my choice but you need to be aware if you lift a wheel you lose drive with them.

 

[Shane001]

yeah, that's what worries me about the torsen, I'm thinking Oran Park

At speed or through corners will this unsettle the car?

 

[IJ.]

It's only in really high G low speed corners where you get a rear lifting.
(or if you hop a ripple strip at speed)

It feels like bad clutch slip, the TrueTrac I got for my 9" has a preload pack to prevent this happening.

 

[Shane001]

(or if you hop a ripple strip at speed)

aka Oran Park, just about every ripple strip gets hit hard, especially the dog leg

 

[prsrcokr]

Good point IJ, this may be the reason I've had a couple snap spin situations in hairpin corners. I had forgotten how the Torsen is a multiplier but anything times zero is zero. There is always learning to anticipate this, you can get a lot of traction out of it.

 

[Wiisass]

When I finally get around to buying a real diff, I want the ATS Carbon 1.5 or 2 way. It's a clutch type, but has nice, smooth engagement, so no unsettling like a metal clutch type. Now I would just need to find someone who can still get this stuff for me.

 

[Grimsta]

I'd prefer to be running with a spool but for the money it's gonna cost to have a custom spool made up I could by a Kaaz 2 way instead!

In my own opinion if it where me id go with the Kaaz 2 way or the 1.5 clutch LSD! The stock JZA70 4:10 diff can only hold so much power to the wheels before they fail. And a 3.73 may have to long of gears for short track racing.

<---- Has KAAZ Group Buy goin on.

The KAAZ's take a beating even if they are clutch type. They're well known for durability. Going through 3 Torsens is INSANE, although I do like the theory of the torsen in the end I would go with KAAZ because of the line I have them but other than that because of their durability as I seem to thoroughly beat my crap into the ground.
BTW there is no 1.5way KAAZ for the A70 chassis, only 2 way. But you can rearrange clutch packs manually to work for you if you know what you're doing

 

[Shane001]

What about the TRD 1.5 way / 2 way? Are they any good?

Has anyone actually run with a factory clutch LSD on the track, ie the 3.7 or the 4.55? I want to try these back to back on a practice day to see what lap time difference I'm getting with the 2 ratios. But don't want them failing on me otherwise I won't get any money back on em! :biglaugh:

To explain, I have to run a 36mm restrictor on the intake to the turbo (category regs), which effectively chokes boost as the revs increase. So my power curve drops away to nothing from 5500rpm. At 5500rpm with 4.11 gears, my top speed is only 217kph. At one of our major tracks in NSW (Eastern Creek), I'm hitting top speed way before the end of the main straight, so with 3.7 gears I'll be hitting closer to 240kph. What I need to test is the affect on acceleration...

 

[BorHor]

Factory diffs can get the job done if they are rebuilt or in really good shape. The main downside is that they go bad quick.

 

[Shane001]

So they should be OK for about 40 to 60 mins track time each on a practice day? Good, good, only way to know for sure is to test

 

[BorHor]

Yeah it will work.

 

[IJ.]

Shane: If you're going to run it at high speed I'd look into a pump and cooler and plumb the return between the Pinion bearings.

Both my G series failures happened at high speed due to oil starvation to the front pinion bearing.

 

[Grimsta]

I hate my factory diff.
<--- Cant even afford his own KAAZ GB, lol

 

[Shane001]

Shane: If you're going to run it at high speed I'd look into a pump and cooler and plumb the return between the Pinion bearings.

Both my G series failures happened at high speed due to oil starvation to the front pinion bearing.

What center were they? (torsen, factory clutch, etc)

What if I just ran a little extra oil? Reckon this would work?