Dknebes

Which is better. I will be primarily on the street but will see track time. Also who has the best price? As you may know this is high hp and will be around 800hp at the crank. Thank you in advance.

David

Brian W.

Id also like to know what type of differentials most of you use on the track. Are they helical? or clutch type? I know the Qauife is a helical. Who makes this "GT" LSD? Im looking into differentials over the winter, the one im interested in is Clutch Type with Carbon/Kevlar Clutch plates, from a Brand Name i use and trust in Japananese cars.

Dknebes

I have ordered a Quaife after talking with a number of well informed people. The web site for Guard Transmission is http://www.guardtransmission.com. I made the decision based on my application and hp.

David

Sameer

Guys,
I too will be rebuilding my g/box soon.
What should I upgrade to make it stronger?

Quaife or GT lsd?
Steel synchros?

Dknebes

I talked to Paul at GT. He said you should not put a torque biasing differential in a turbo car. He recommended a limited slip or keep my LSD in my 89 and rebuild it. My engine builder has installed over 15 Quaife differentials including his own 800hp Porsche. He said they worked great and never had a problem but said he saw many stock LSD differentials fail in high HP cars. It is always the same; it depends on who you talk to. You finally have to make a SWAG (scientific wild *** guess). Ok have to give you another one. The 7p's (poor prior planning produces **** poor performance)

David

Randy

I could be wrong, but I think clutch plate type diffs have the ability to limit unwanted changes in wheel speed under braking and deceleration unlike geared types, which just coast. This is supposed to help stabilize the chassis under heavy braking.

Dknebes

That is correct, but they are used in race cars. The people that I talked to did not say they had problems with deceleration at the track. I will know soon and post my observations.

David

Brian W.

I acutally USE a Clutch type LSD in my Nissan 240sx(its turboed). It performs great!!! and is very smooth and predictable. I think i will be using the same one in our 964 Turbo when the time comes. However, to my knowledge no one has used this LSD in the US in a Porsche.

Randy

I could be mistaken, but I believe the G50/50 in my 930 has a clutch type LSD. It works very well. My car is a fairly heavily modified track and street car with 480 +/- h.p., and the operation is mostly transparent.

Dknebes

If it is a 5 speed G50/50 it has LSD. My car is an 89 with LSD but I will be running 800+ hp. My car with 700 hp worked well but it only has 8000 miles with that hp. I have the engine out now so wanted to update and was told the stock dif will have problems down the road with all the wheel spin and will wear out the friction plates in the stock diff. I would rather replace it now than have to pull the engine and trans later. I would think you should be fine with your application.

David

Randy

Thank you, I can see your point.

Sameer

Guys,
Pardon my ignorance but does my 81 930 come with LSD? If yes, isit worth changing to the GT or Quafe LSD? My rides about 450bhp and I use it mainly for street racing and it sees the track once in a while. Pls advise.

Dknebes

I am not sure but I think 87 and up. I do not believe you have in an 81. If you do a hole shot see if one or both tires spin. If the car is jacked up on one side without LSD that tire will spin if it has LSD it will drive off. Or do a new post on the board.

David

Sameer

David,
Thanks. Will check it out.

mochman

The GT diff and the porsche l/s I believe are both lock up type units ie you can set the lockup percentage like lock-up under decel which allows you to trail brake etc more eff. Of course this requires disassembly of the trans. I had a guard it's killer, quafe is a torque biasing unit okay for street but a guard would be better the build quality of a guard is incredible, call paul he will send you info to help make a decision I would never change mine.