LSD

[Fred W.]

Hi All

I have a Porsche G50/01 transaxle which looks to be in good shape as far as I can tell at this stage IE its not yet in the car . Its a standard box that will be going on the end of a Holden Special vehicles LS2. I really would like to know what the advantages of a Limited Slip Diff are for a car that's really only going to be driven on the road, all be it with some degree of enthusiasm, and perhaps the odd track day. The engine is a powerful one even in standard condition. How would LSD be any advantage? Would it make the car 'nicer' to drive? safer to drive? any thoughts. Thanks.

 

[Jack]

The problem with a conventional, or 'open' differential is that when one of the wheels slips, the drivetrain is not able to provide power to the other wheel. Basically, if one of the wheels starts to spin (not gripping the road), and additional power travels through the past of least resistance - the spinning wheel. Though this is usually not a problem, cars designed to go fast (race cars and sports cars) could go faster if this didn't happen. Thus, the limited slip differential. The construction is such that even if one of the connected wheels starts to slip, some power from the drive train is applied to the non-slipping wheel. This allows more power to be translated into speed in these conditions. Cars with limited slip differentials (or LSD) tend to accelerate faster, but are harder to turn, than non-equipped cars. With the LS2 engine in a lightweight car
IMO, an LSD is advantegous as it gets power to the road without excessive wheelspin (use your head here). In this light car anything over 300HP or less than 8 pounds per HP all up will perform. Get the power to the ground!<!-- }1197209 --><!-- google_ad_section_end -->

 

[Howard Jones]

The difference in My GTD was so great that it was like driving a completely different car on track. I had a Quaife installed in my Renault R21 and the effect was that it felt like the car had a hundred less HP. What I mean by that is, the point at which the rear tires are at their limit under power is so much greater that where I was being careful not to spin the tire and go into huge over-steer I can now just mat it and it goes like hell. No drama just hard full power acceleration. If it does break loose it is a nice progressive slide with both tires doing the same thing. Same grip same slip angle.

The old way was good grip to NO grip when the tire started to spin and then big over steer. Then if I reduced power to try and catch the slide the car would gain traction and snap back the other way. Ugly to drive like that and it's a miracle I never wrecked the car. It is also very slow on the lap. The best and easiest way to lower lap times is to get ONTO the longest straight at the highest speed possible and that is done with corner exit speed (grip!). Anyway the nastiness is completely fixed now.

I would NEVER build a GT40, or for that matter any mid engine car, without an LSD of some kind. These cars are light, rear engined and prone to over-steer under power. Then because of the polar moment effect of the weight in the rear of the car they are more difficult to "catch" once they loose traction at the rear. The solution in to use BOTH rear tires to put down power.

The added cost of a good LDS unit is less that a premium set of tires. Why would you put good tires on a car and then not be able to use them. The car would be faster with a LDS in it and tires at half the price of the premium set without a LSD.

Do it! Do it now at the beginning and save the grief of taking it apart and doing it right the second time. This has become my motto.

 

[Jack]

Well presented Howard, thanks...

 

[Fred W.]

Thanks Howard , more fun and safer! what else does anyone need to know?

 

[Erik Johnson]

Hey there Fred, I just replied to you other post with regard to your G50 options. There is one thing that I wanted to make sure you understood with regard to changing out the differential.

It is NOT a plug and play option. You will need to ensure that the ring and pinion has been reset correctly and I would recommend taking the further precaution of blue printing it as well.

This is very important as you can do substancial damage in a short amount of time if this is not setup right.

Just trying to help.

Erik Johnson
Carquip Sales
(303) 443-1343 ext 2 work
(720) 980-9407 cell