LSD, Worth the money? Options

[ppickerell]

For an AX car with some fast street driving, is it worth the $2000 (IMG:style_emoticons/default/icon8.gif) for a LSD? The tranny is out and being totally rebuilt. That's some serious coin on top of all of the rest of the money being spent on this car.

[TimT]

do you want to compete? or just show up and play?

LSD makes a difference

[bob91403]

Somebody correct me if I'm wrong here. Quaife - yes, LSD - no?

[TimT]

Quaife - yes, LSD - no?

Quaife=YES LSD =YES

either option is better than an open dif.

[ppickerell]

Quaife? What's the difference?

[TimT]

Quaife/Torque biasing unlocks on decel

LSD (disc or plate type) works in both directions

[bob91403]

I thought the difference was that quaife used gears to eliminate wheel spin, and LSD used friction and could be ordered in different ratios. Also that quaife lasts longer.

[TimT]

I thought the difference was that quaife used gears to eliminate wheel spin, and LSD used friction and could be ordered in different ratios. Also that quaife lasts longer.

yes the quaife/torsen/torque biasing dif uses gears

the plate LSD uses shim plates to keep the dif locked,

the quaife.. etc works when you are driving against the gears.. ie accelerating. although as soon a you brake the dif opens...

the plate keeps the dif locked to a percent, whether accelerating or decelreating

[campbellcj]

If you've got the bandwidth, this article might help.

http://www.nosubstitute.org/articles/LSD_V...Velocity_Feb01/

I can PDF it into a smaller file Monday if that would be helpful to anyone.

[campbellcj]

Or if you have bandwidth now and want a cleaner copy (PDF of entire Velocity issue), here ya go --

http://www.nosubstitute.org/articles/Veloc...01/february.pdf

[ppickerell]

So you have $1295 for a quaife, and $2000 for LSD. Which should I hang on my car? It will have a freshly rebuilt but stock 2.0.

[campbellcj]

What is your current/intended use for the car? I think conventional wisdom is that for autox the TBD (i.e. Quaife type although GT makes them too) is fine or even better; and for track use you want a real clutch type LSD. For street, honestly unless you are traction-limited due to massive torque or slippery conditions, the cost-benefit is tough to justify IMHO.

Whichever way to go, be sure to email or talk to Paul Guard (GT Transmission) as this is his specialty and his diffs are top notch.

(edit) oops I just re-read your original post where you say AUTOX. I do not have a ton of autox experience but again I think a Torsen/Quaife type TBD is generally preferred for that usage.

[bob91403]

From what I know I'd go with the quaife. Nobody addressed my question about wear. If the quaife is gears, and the LSD is friction can you guess which one will wear out first?

[TimT]

So you have $1295 for a quaife, and $2000 for LSD. Which should I hang on my car?

I would go with the LSD.. and spec it at 80/80

but that is if it were for my car.

A quaife is a great dif... and may be everything your looking for

[ppickerell]

In the article the author states that the torque biasing style is vastly inferior. I assume the quaife is considered a torque basing diff? So this seems to be cut and dried in favor of lsd or "always on" There goes another $750. Bring on the LSD Mr. B!

[bob91403]

80/80? I thought it was a ratio? You know, adds up to 100. Like 70/30, or 80/20.

[campbellcj]

Good point re. wear. If you drive your car on the street a significant amount then this would be a factor. IIRC Otto told me they use to set up the ZD LSD's at near 100% lockup during rebuilds because then they'd soon be at the desired 80% and loosen up through the year; then rinse & repeat for next season. I suspect the new units with improved materials & techniques may hold up a bit better but they are still friction based mechanisms.

Then again, there is a point on the slippery slope of autox or TT or race competition where you are most likely tearing down the trans every season or two anyway...in which case the cost delta between diff types is probably not huge.

[ppickerell]

Intended use? I would like to put in shit loads of seat time along with my son next year in AX. I would also like to do some type of DE this year to improve my skills. I only attended one event last year and I am pretty well hooked. So I want to have this car set up right!

[brant]

this is a timely re-address thread...
I'm working out the details for a different race tranny and had a long chat with my race guru out here, Alan Johnsen..

I had always thought exactly the above: LSD=track and TBiasing=autox

I do (did?, dang its been a long time building this new car) track driving, and even have a locked diff in my current race box that I just got freshened....

So long story short, I met with Alan and he insisted that with my small motor (2.0S/6) that I don't want to run a LSD, and will ultimately be faster with the TB....

he said that in the lower HP applications, the LSD is creating too much loss
further the TB would be smoother again for the lower HP situations....

I've got to say I trust this guy implicitely...
when he built my Locked diff tranny the first time, he cut my personal best by 2 seconds... I'd put his advice against anyone out there...

so like I said I'm a little bit befudled... I'm going to go ahead with this furture box.. It's pretty trick as you loose reverse but move 2nd down into that slot.. I'm going to go with his advice and put the TB into it. Guess I'll see how it compares to a 100% anyways.

brant

[ChrisFoley]

An open diff is best in a low hp car. The only losses are at the wheel/'pavement interface, which should be controllable with the driver's right foot. This is especially true for DE. At an AX you may feel otherwise.
A LSD or TB diff will have internal friction losses and consequently will heat up the gearbox.