MarcD147

I have seen people add it as the Porsche one "seems" weak...

What are the benefits from a technical perspective? I would love to understand the details.?

How and when will I feel it in the track?

Are there any downsides? Factory Warranty?

jphughan

You'll feel it as increased stability under hard straight-line braking (as opposed to rear end wiggle that you would feel when the stock diff is on its way out) and in the ability to put more power down on corner exit since you're not wasting as much torque spinning the inside wheel. As for downsides, nothing meaningful that I've seen reported from the very large population of 997 owners that have been running Guard diffs for a while now (might want to search, since there are many threads about them), but theoretically if you chose an extreme diff setup like 80/20, it would impair your street driving on slow corners -- so just don't do that. Most DE/dual purpose folks seem to choose 50/50 or 60/40 from what I've gathered. Other than that, it does require periodic servicing by Guard, so your car will be out of commission while you have the diff removed and shipped to them (can't remember the exact interval that GTGears recommends, but it's been posted in various threads here many times as well), and you do need to have the initial installation performed by an authorized shop, which you can find here (http://www.guardtransmissionllc.com/dealers/), but the subsequent removals and reinstallations for servicing can be done by any decent shop, I believe.

What happens to the factory warranty seems to depend a lot on the dealer you work with. Some have a reputation for maintaining the warranty as much as possible despite various types of mods, while others take a harder approach. Some might deny warranty coverage for anything gearbox-related after you had a diff installed since the diff lives in the gearbox, and worst case any issue that might have been caused by an aftermarket diff could have coverage denied, but again you might want to read some of the many existing threads on Guard diffs to find out what the warranty experience has been for actual owners.

Bill Lehman

On my 987.1 the most noticeable difference was the vast improvement in stability under hard braking as mentioned above. I also noticed a reduction in wheel spin exiting slow corners. When I ran it for the first time at Summit Point I had an immediate reduction in lap times with no other changes. I went with a "street friendly" 60/40. Bodymotion did the work but I'm sure the Dougherty would also be a good source.

MarcD147

that hard braking improvement would be a big benefit as this weekend hitting the brakes at 155 into the bustop or 163 into turn 1 at Daytona are heart stopping moments....

similar for Sebring T7 a week ago...

need to check this out

how does it influence the TC and ESC? I run with those on.....

digitalrurouni

My understanding would be that because of the added stability, it would rather reduce the TC and the PTV etc intervention. Which is a good thing as I absolutely don't like PTV. Perhaps the TC intervention would even become smoother. This is my personal theory anyway.

Alan C.

This is a good topic for those beginning to track their GT4. The factory diff will wear out. If you drive it hard that will be sooner than later. The problem is it is 'wearing' out not breaking. So the benefit goes away on a slope not a ledge. You adapt. Braking and corner exit are both improved with the Guard unit. Talk to Guard about what you want. They can tell you what you 'need'.

GrantG

PTV works by causing the car to yaw into the corner by independently applying the inside rear brake. You could have reduced effectiveness of this function if the locking of the LSD under braking is much stronger than the factory LSD, as braking the inside rear will also brake the outside rear (with reduced yaw effect) - will act more like a solid rear axle.

Guard LSD's are great (have one on my 911) and they can be ordered with a variety of locking ratios - I'm sure you can select one that will work well with PTV, but this should be considered when ordering.

Yargk

What was the lap time difference?

sharkster

Even on the twisties and just about every test any journalist has done with mine (equipped with the Guard LSD) vs the stock one you can and will feel the difference. One on drive I was behind my modified car with a stock one (and some miles and likely worn out stock lsd) the car in front would bite down on power/breaking and pull away while I'd be wiggling and struggling to put the power down. The 50/50 locking factor 4 plates per side for a total of 8 plates. Moderate pre-load to make it manageable on the street and have good lifespan of internals, but still gives really good bite when driven hard on the track or backroads. Then obviously on track... Quite possibly the single best most important mod to the car. Factory friction plates just sheer off anyways.

MarcD147

i was thinking some more about this but couldn't figure out why a guards LSD would result in improved stability under hard braking?

what causes the instability under braking. just the weight transfer?

how does the LSD fix it?

Bill Lehman

I've sold the car and deleted most of my data from that car however, I remember a lap time reduction in the 1.5-2.0 second range at Summit Point.

Bill Lehman

On the GT4 I think the main culprit is rear toe steer caused by weight transfer. The LSD locks the rear wheels under deceleration/braking keeping them at the same speed and preventing one wheel from locking up. The 987 also had issues with ABS causing "Ice Pedal" and I believe the LSD helped with that.

Yargk

Thanks for the info. That's huge!

breljohn

Resurrecting this thread.
Factory LSD died on my 987.1 GTB1 Cayman.
Does anyone know if i can send the factory unit to Guard to rebuild the internals?
Any recommendation on ratios?
Thanks

BillC3

I'm pretty sure that Guard won't rebuild a Cayman diff and doesn't have the parts to rebuild them either.