Prior to tearing down my OEM LSD Monson told me that my preload was not even measurable, but the plot thickened once the unit opened up. Your car has obviously been driven the way Ferry intended it to be driven, was his comment, and noted that my plates were blue due to heat, something he has only seen on GT2s. He also observed that some of the plates and friction discs showed little or no wear on the inside edges, but noticeable wear on the outer edges, indicating that the factory plates were not flat and true when new. Again, interesting.

With the freshly rebuilt Guard LSD installed and the transaxle filled with fresh Mobil 1 Delvac synthetic gear oil this project is again ready for action. Note that this gear oil contains no friction modifiers, and that after 1,000 miles on the street or a full day at the track you should change the oil, as this will flush the transaxle of any particulate matter created while the LSD friction discs get settled in. The life of the LSD will depend on how much track time the vehicle endures, but a combination of street and DE track days will very likely see the LSD lasting until the transaxle is rebuilt. My first impression after driving the car for the first time with the rebuilt diff was enlightening. I was able to feel the LSD truly working in the corners; a more than subtle feeling of stiffness and grip in the rear. Clearly, my factory LSD was completely shot. The new unit works quietly too, but I did notice that the GT3 exhibited a touch more understeer in low-speed corners with the more aggressive LSD. Perhaps some sway bar adjustments will be in order to tune the handling when we get back to the track in the spring.

In the next installment we’ll attempt to lose some weight, add some power, and improve our handling, all in one giant leap. Any guesses?

One additional LSD wear test
I performed one final test before making my decision. This was blocking the front wheels and lifting both rear wheels off the ground. Then, with the car in Neutral and the e-brake released, I hand-turned one of the rear wheels. The other rear wheel stayed stationary, likely indicating a very weak preload. After all of this, I was pretty sure my LSD was pooched. A strong, working LSD allows the other wheel to turn in the same direction (a regular open diff will turn the wheel in the opposite direction).

R&R GT3 LSD
With the GT3 safely on a lift or axle stands, remove the rear-most undertray to access the transaxle and driveshafts. Drain the transaxle gear oil, and remove the T-50 bolts from the inner driveshaft to the differential output flanges. Loosen and remove the central flange bolts and carefully pull out the flanges. Next, remove all 12 bolts from the left side of the transaxle differential casing and then gently, with a wooden peg or hammer end, tap out the differential cover. With the left-hand driveshaft out of the way (and being mindful not to damage the coolant hoses above), gently and carefully, with a firm, clean grip (fresh and dry latex gloves), remove the 30-pound LSD unit from the transaxle. You will have to be very patient and try several orientations to get it out. Reinstallation is the reverse, but lubricate the end bearings first and pay special attention when meshing the ring and pinion gears and inserting the output flangeseverything should rotate smoothly upon testing by hand with the transmission in Neutral. Torque up as per the manufacturer specs. Work time is approximately 2.5 hours for removal and about the same for install. Take your time and have fun!

Properly packing your LSD for shipping
Be sure to protect your valuable and very heavy LSD when shipping. Believe me when I say you don’t want to have to buy another unit if yours gets damaged en route. Pack it twice: first into a small box with plenty of bubble wrap and paper, and then into a second, larger box stuffed with paper on all sides. This will prevent it from settling and rolling about in transit. The sucker weighs 30 pounds and will move around if you don’t pack it correctly. I speak from experience; fortunately, I was lucky. Now, read this paragraph again!

By Doug Neilson
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