Guard LSD - in a 74 freshened coupe - how will it be different???

[chrismorse]

Hi Guys,

CMS is going through my 915. I asked them to put in a Guard 40/60 LSD, amongst other improvements and I am curious about how different it will feel/perform.
Background, 74 stock CIS, fresh brakes with cooling, slightly upgraded suspension, ER bushings, Bilstein HDs, 21/27 t bars, 20/18 Carrera bars, 195/55 Dunlop direzzionales. This is primarily a fun car with a few track days anticipated.
What will feel different??

I am looking forward to the car having a little less oversteer on corner entry and better traction.

Is tire mileage significantly affected?
Will it be in any way intrusive??

despite the eye watering costs, I am looking forward to getting back on the road.
Thanks,
chris

[Larmo63]

You will feel more 'planted' on the road. Your car sounds rad, let's see pictures?

BTW, what ER bushings did you use?

[3rd_gear_Ted]

Downshifts should feel more settled and this allows easier straight line braking in a low HP car.

[Bill Verburg]

Originally Posted by chrismorse

Hi Guys,

CMS is going through my 915. I asked them to put in a Guard 40/60 LSD, amongst other improvements and I am curious about how different it will feel/perform.
Background, 74 stock CIS, fresh brakes with cooling, slightly upgraded suspension, ER bushings, Bilstein HDs, 21/27 t bars, 20/18 Carrera bars, 195/55 Dunlop direzzionales. This is primarily a fun car with a few track days anticipated.
What will feel different??

I am looking forward to the car having a little less oversteer on corner entry and better traction.

Is tire mileage significantly affected?
Will it be in any way intrusive??

despite the eye watering costs, I am looking forward to getting back on the road.
Thanks,
chris

How intrusive depends on the preload, generally the asymmetrics are set up on the loose side so not intrusive at all

I have a 40% ZF in one car which is a tad intrusive in tight parking lot type situations the PMS 40/65 in the other car isn't intrusive in any way at all, it just works, best effect is braking closely followed by corner exit

[Matt Monson]

Originally Posted by Bill Verburg

How intrusive depends on the preload, generally the asymmetrics are set up on the loose side so not intrusive at all

I have a 40% ZF in one car which is a tad intrusive in tight parking lot type situations the PMS 40/65 in the other car isn't intrusive in any way at all, it just works, best effect is braking closely followed by corner exit

That may be generally true for factory stuff, but doesn’t apply to mine really at all.

How I set it up is determined by the customer order. For a street car or DE special I generally make them invisible in a parking lot or your neighborhood 25mph streets.

[spuggy]

For acceleration in low traction, any LSD will prevent one wheel uselessly spinning while the other does nothing. Think "smoking the inside tire" on hard cornering.

In low-traction conditions, an extreme example (eg UHP summer tires in cold rain after a dry spell), you may notice that this results in you crabbing along the camber of the road maintaining direction with counter-steer... This is actually a lot of fun; the alternative is that one wheel gets all the power and steers the rear of the car violently and too fast to correct - which is actually no fun at all.

In practical terms, you're most likely to notice this effect pulling out of a gravel parking lot - an LSD will "scrunch" from both rear tires.

On deceleration, a 40/60 asymmetric will nail the rear end down and eliminate the "floaty" feeling at the rear of the car when prudence suggests that you don't adopt a 8/10ths braking point and prefer to slow down by using less throttle instead.

Originally Posted by Matt Monson

That may be generally true for factory stuff, but doesn’t apply to mine really at all.

Can confirm.

Got a Gripper 40/60 for my 915. Set it to 80 ft/lbs, ran it for 6-7 years. Best single modification I made to the car - I hadn't thought it'd make that much difference, but it was night and day whenever you noticed it doing its job.

it would clank a little loading/unloading the ramps and push slightly in parking lots/slow speeds. You adapt quickly to the latter; not a big deal - and a no-brainer tradeoff.

I bought a GT for the G50, discussed setup and usage with Matt, who agreed the same specs. Seem to recall his ramps were actually 35/65. Looked a lot prettier on the bench.

In comparison, the GT doesn't clank at all reversing out of a parking space and loading it up to drive forward. Been in for the last 6 years & works flawlessly. You just don't know its there at all - until it does its job and you congratulate yourself for having it fitted...

The small amount of turn-in push at slow speeds inherent to an LSD doesn't go away, but after a while it just doesn't register anymore.

I like 80 ft/lbs with a 35/65 asymmetric in a lowered/stiffened (21/30 TBs and 3.2 sways) SC body 400+HP turbo with 17" wheels and sticky tires (225/45 & 255/40 Falken RT615K). I think it drives great - supple, predictable, responsive, nearly stiff enough to control progressive power squat at the rear, few surprises/vices. If the car were 100% track, i'd make some changes (stiffer suspension & sways) - but for a car that's primarily street-driven and visits the track at most a few times a year, this works pretty well for me. YMMV...

If desired, you could get less push with a lower setting; discuss your car, its setup and your preferences with someone who knows.

[Bill Verburg]

Originally Posted by Matt Monson

That may be generally true for factory stuff, but doesn’t apply to mine really at all.

How I set it up is determined by the customer order. For a street car or DE special I generally make them invisible in a parking lot or your neighborhood 25mph streets.

I should have phrased it better, the asymetrics are so much more effective that they don't have to be set up w/ as much preload for the same effect

[chrismorse]

Thanks Guys,
Appreciate all the input & experience.
Matt, Roger, (CMS) should be contacting you shortly, Looking forward to your recommendations.

Here is the requisite photo:


chris

[Driven97]

I have an (alternate brand) LSD and the only time I notice it negatively is when I'm reversing while turning. Applying torque in reverse locks it pretty hard and you can feel it really resisting from letting the car turn.

Under power I no longer have the one wheel peel that I had, though in extreme circumstances I have noticed the inside tire slip ever so slightly. The car is also more stable in lift-off throttle conditions, though you are still plenty able to initiate rotation. It's just smoother and more predictable.

A 100% must have item if you plan to do legitimate performance driving with a 911. For a car that spends 99.5% or more of its time on the street, not really necessary but nice to have.

[Matt Monson]

Originally Posted by Driven97

I have an (alternate brand) and the only time I notice it negatively is when I'm reversing while turning. Applying torque in reverse locks it pretty hard and you can feel it really resisting from letting the car turn.

Under power I no longer have the one wheel peel that I had, though in extreme circumstances I have noticed the inside tire slip ever so slightly. The car is also more stable in lift-off throttle conditions, though you are still plenty able to initiate rotation. It's just smoother and more predictable.

A 100% must have item if you plan to do legitimate performance driving with a 911. For a car that spends 99.5% or more of its time on the street, not really necessary but nice to have.

You have a Wavetrac, which is not an lsd. It’s a torque biasing gear driven differential. A gear driven diff behaves exactly like an open diff until there is any wheel spin.

The reason it locks hard in reverse is their gimmicky ramps. It is in fact 100% locked in reverse as a result.

[Driven97]

I have a KAAZ actually, which is more traditional than the wavetrac. Set up as a reverse 1.5 way with one of the 3 sets of plates disabled, and the SuperQ WPC coating.

[Matt Monson]

Originally Posted by Driven97

I have a KAAZ actually, which is more traditional than the wavetrac. Set up as a reverse 1.5 way with one of the 3 sets of plates disabled, and the SuperQ WPC coating.

My apologies. I’ve confused you with another member here.

[Driven97]

NBD, tried to keep the "alternate brand" out of the thread to avoid muddying it.