LSD recommendations, LSD reccomendations Options

[Charles Freeborn]

Greetings.
While my engine is out for top end refresh I'm also planning on installing a limited slip diff.
What have people run and why? Obvious choices are Guard (true LSD) Quaif, Wavetrac (Torque bias). Pros / cons of those types? I've heard the TB is easier on the rest of the gearbox. Not too concerned about having to run LSD additive as the fluids get regular service anyway (every event).
Quick rundown of the car:
100% track use (not street legal) Little to no AX - all road course.
2.0L 4 cyl with fairly extensive mods. Estimated hp around 150.
901 side shift with AFKSX gearsets.
Car weighs approx 1700 lbs (18 & change with me in it)
Currently running Toyo RR 225/50 slicks. May step up to Hoosiers if I get more serious about racing. I've got another set of wheels for running in the wet with R888R's. Not great rain tires, but that's what's on those wheels now. When they're done I'll probably switch to RA1's.

Thanks!

[campbellcj]

I went with a Quaife TBD many years ago for same reasons Brant cites, probably after speaking with some of the same people LOL. My car does have enough power for corner-exit traction to be an issue. Especially as I favor and was set-up for tighter technical tracks the conventional LSD's impact on low-speed turn-in /rotation would have sucked. Although I would've liked the decel lockup for sure, decel stability not being a strong suit of the 914.

My trans is about to be opened up and trying to decide what to do - I may ultimately have another one built w/ longer gears and a different diff, as this one is extremely short-geared (AGaKQV IIRC) though the car does rev to 7800 so top speed not an issue. Don't really wanna go more than about 135 in this car w/ no aero... But the car is quasi-streetable again now and cruising 4500rpms on the freeway is no fun.

I do have an LSD in my 911 and can really feel that; it was added after I bought the car after a rebuild with Guard internal bits so I experienced the before & after. In that car it's a huge plus, a lifesaver really, with the massive torque and rear engine.

[stownsen914]

Two disadvantages of the TB differentials:
1. No lockup on decel. Maybe not as big a deal as on a 911, but I wouldn't say it doesn't matter.
2. The biasing only works when both wheels are on the ground. If you lift a wheel, your freewheeling just like with an open diff.

Certainly better than an open diff. I'd never heard that TB differentials were faster in mid engine applications. I'm sure driving style is a factor too, so for some I'm sure a TB is faster, but maybe not for all.

I wonder what pros are running in modern mid engine cars. I'd guess LSDs, but I don't know.

[jd74914]

...the conventional LSD's impact on low-speed turn-in /rotation would have sucked. Although I would've liked the decel lockup for sure, decel stability not being a strong suit of the 914.

I don't really understand the low-speed rotation impacts? Could someone explain?

Most higher end clutch LSDs are Salisbury (ramping) type AFAIK. Certainly you'll get something similar to a locker if you have excessive preload. Belleville washers were used to hold everything together in original Salisbury iterations (40+ years ago). These have issues with high preloads due to their limited "travel" range. Some newer versions have springs holding the ramps together. This means quite limited preloads are needed (obv. can add to personal preference) which to me implies more "open diff-like" turn in behavior when traction is good. The ramp angles can then be set on both the accel and decel sides to tune for the car. I know its a PITA to do this when you have to disassemble the gearbox.