Babalouie

That wavetrac diff looks an awful lot like a TBD on the inside Seems to work on the same principle anyway, with all those helical gears around the circumference. There is a friction thing in the centre (the green part in the animated picture) to sorta give it "some" of the function of a normal LSD, but most TBDs have something like that anyway.

It'll feel like a TBD to drive, I think.

Steve Weiner-Rennsport Systems

From what I've seen of those Wavetrac's, they unlock on trailing throttle, just like other TBD's.

mcipseric

I am no expert, however, hard braking with the Wavetrack seems more controlled than with the LSD. I get some uncomfortable rear wiggling when braking and down shifting very hard on the track with the LSD.
I welcome any comments from anyone with more track experience to explain what is going on.

GTgears

It's a rare day when I get to correct Bill, but in an instance like this I am sure that he won't mind. We've offered 80/80 LSDs for quite a few years now. Obviously for pro-level motorsports type use only.


We've also added 90/90 on top of that for one specific application, our 935 LSD. The logic there is that 935s are taking out a spool and to minimize the changes to set up of the car while still giving the benefits of an LSD 80/80 or 90/90 will be best. But that's really more of an aside to it all.

Along the lines of what Steve said, I have recently sold a couple of LSDs to people who had tried the Wavetrac and didn't like it. What has been reported to me is that it does not lock up under braking in way that it has been advertised and that in their experience it was similiar to a TBD. I've never driven one or handled one, and am only passing on what I was told by two different customers I talked to.

Also, as a bit of an aside, one cannot make any reasonable comparison to a FWD front engine car and a RWD rear engine 911. People coming from other chassis configurations always get confused when we first start talking locking factors on 911 LSDs. If they are coming from an M3 or a GTI or pretty much anything else, they are used to an LSD that has more lock up on acceleration and less under braking. The first time I say 40/60 they respond with," Don't you mean 60/40?" The 911 (and more recently the Cayman and Boxster) are unique in how we tune their LSDs. Most of our customers don't realize that we set their 944 LSDs as 60/40. But when it's a 911, it's the other way around because of that heavy weight of the engine out back and the pendulum effect. Lock on braking really settles down the rear end and lets the car brake straight and true with a minimum of wallowing.

Steve Weiner-Rennsport Systems

In order to offer some input on this, I'd need to know which LSD do you have,...the OEM factory one, Motorsports one, or a Guard?

GTgears

On the previous page he says it's a freshly rebuilt PMS unit. In my experience when a car exhibits those traits with a good LSD in there it's an alignment or other suspension set up issue.

Steve Weiner-Rennsport Systems

Ahhh,....I missed that.

Yessir, that's a chassis/alignment/setup problem.

Mark in Baltimore

Yep, your LSD should be providing significantly more stability under braking than without it. It really allows you to brake later into the corner and inspires confidence in carrying that much more speed.

camlob

Thanks for the info. I just sent you a PM.

embacpa

i have a wavetrac tbd and experience too much wiggle under hard braking. have had it for one track season. i am moving to guard lsd. so, i will have a slightly used wavetrac tbd for sale if anyone is interested.

mcipseric

Problems solved.... too much engine braking.... no setup or LSD issues. Driver issue!

SleepRM3

Interesting. For those of us who don't track their 911s, is the WaveTrac acceptable? I drive mine in snow/ice conditions.

vincer77

Very helpful thread. So if I understand correctly, the locking up of the LSD under braking provides evenly distributed engine braking torque to the rear wheels, stabilizing the car. Would this be similar to adjusting the brake bias for more rear braking? What is the advantage to having the LSD provide this vs adjusting brake bias.

I do not track my car, but I do experience an unnerving "wiggle" under hard braking in my non-LSD cab. Sounds like an LSD can cure this. Can the stock braking system brake bias be adjusted?

race911

Well, you're not braking only in a straight line if you're out there on the ragged edge. So figure in the sideways weight transfer, and it will be pretty clear that a mere bias adjustment rearward can make things incredibly tricky.

On point 2, braking that hard into a corner on the street? Let's put it this way, say I'm running to my capability in the yellow car on track (~2:00-1 at Thunderhill), if I dial it back say 4 seconds/lap (passenger pace) I'm probably in the mental state of being able to carry on a conversation, text, eat, whatever. Comparing that to aggressive street driving would probably equate to a 2:20 lap. And at that point you aren't even coming close to anything the car is capable of, braking and cornering-wise.

Steve Weiner-Rennsport Systems

Aside from what Ken offered, a properly set up Guard LSD eliminates that rear-end wiggle under hard braking, even on the street.

I'm assuming that your rear alignment settings: static & kinematic toe, are perfect.

It not easy to change brake bias on a stock 993 unless you either replace the calipers and rotors with something like the 993RS package (and that requires a good LSD!), or install race pads of different compounds which is impractical and in some situations, unsafe. Stock 993 brakes really work VERY well for the road,...