PCA SDR

Looking for information on the pros and cons of each of these types of differentials. Would welcome on-line technical articles or personal experience. I'm thinking of installing one on my 993 to help with my excessive wheel spin when existing a corner. Even though I am doing mostly AXs, I plan on doing more TT/DE track events in the future. Thanks

Glenn, the LSD set ups are great in auto-x, even more so than big track due to the big time savings in those really tight corners. On big tracks they play other roles as well as getting out of corners. They are great under heavy braking if you purchase one that has a high percentage of lock up on decel. They are also great on high speed sweepers helping to keep the car planted and power down as the car sweeps. LSD is like any other upgrade to a car, it needs to be done with the entire car package in mind ( suspension, tires, and driver skill to name a few factors).

I have a Guard 50/80 motorsports LSD in mine. I love it, but it does take some getting use to, but once you do, it really feels good and helps plant the car in various situations.

Call me to discuss if you like.

Thanks Kary. In general, I've read that for street/AX applications, the torque-biasing was a better fit. But as you make improvements to suspensions and power, and move up to track events, the limited-slip is a better fit. Just want to make sure before making the investment.

Glenn:

I've liked my Gurads Trans. Torque-Biasing Diff. ever since I installed it (and I put it in for the same reasons you're looking at). Better exit speeds, more predictable drift and over-steer "catch." The Quaiff's are said to be "Torsen" type torque-biasing diff.'s too, but I'm not sure about it. I went with the GT for cost reasons, and I'm happy with the cost and performance of their prduct.

You might contact Jae Lee at Mirage and discuss the heating effect of different differentials in different cars. I recall him talking about certain differentials causing heating issues. I know my GT TB diff. gets the gearbox pretty hot, so I run a synthetic Super Purple or Redline 75-90 wt. lube in the box. I was told if I were to exclusively track the car, to run a 85-110 vis. lube. So, I think there's a possibility of a heat issue. That's the only downside I know of with TB diff's.

I used to have a limited slip diff in my Jeep, that required changing the little clutches on either side of the sub-axles/ring-and-pinion inside the differential. I don't know if this is true of a "limited slip" diff. designed for a Porsche gearbox, but if it is, and the ring/pinion/diff is buried in the center of the transaxle, replacing those little discs could be costly. But, again, I don't know the mechanical workings of a P-car transaxle as well as my old Jeep trans and independent differentials.

Call Jae or John Rickard, or Steve G.. Bend their ear, and get the difinitive data from the pro's in the know.

And enjoy the improved handling. With TB diff's, it's great!

Hope this helps

glenn_993 wrote:Looking for information on the pros and cons of each of these types of differentials. Would welcome on-line technical articles or personal experience.

Go to Paul Guard's site and read his recommendations at http://www.guardtransmission.com/lsd_info.htm The main difference between the clutch-type LSDs and the torque-biasing diffs are that the clutch-type differentials provide lock-up on both acceleration and deceleration. The amount of lock-up on accel and decel can be adjusted by the internal plates. The plates are also a wear item and must be serviced/adjusted regularly for optimum operation. One of the benefits of the TBD is that it requires no servicing or adjustment once installed.

Torque-biasing differentials (like the Quaife) provide lock-up on acceleration only. On deceleration, lock-up is negligible, making the TBD the ideal diff for the softer suspensions and slower speed turns of autocross, without the understeer that a locking diff causes in corner entry. If you like to trail brake and rotate the car in autox, you don't want a diff that locks on decel. If you have a dedicated race car running on high speed, open circuits with a very stiff suspension, and you don't mind a little push in slower turns (and/or have an adjustable suspension to help tune it out), you need the clutch type LSD or a locker (spool). A 40% lockup is a good street compromise, as a full locker will actually cause one wheel to hop in slow, tight turns, which is very annoying in the paddock, parking lot or on the street.

TT