Noahs944

Please describe your dream transaxle for track use.
I am going to buy a 951 or S2 transmission in the future. I'd like a high performance LSD.
What should I go for & where should I buy it?
Thanks.

odonnell

The S2 trans gets a lot of love from track guys, because of the shorter overall gearing. Plenty of choices for LSD of course. The 951 unit has a little taller final drive. Both will stand up mechanically.

V2Rocket

depends what sort of track.
lots of tight corners and short straights? S2 for the shorter diff to grunt you around.

longer straights, maybe not so tight corners? the 951 trans is loooong but with enough power 3rd gear especially is a weapon.

Voith

MAGK944

Droops83

Agreed. It all depends on which tracks you frequent. I would love the shorter gearing of the S2 trans for street driving, but on the tracks I normally run (Willow Springs, Streets of Willow, Buttonwillow, Laguna Seca), the stock 951 gearing is perfect and minimizes the amount of shifting needed.

JustinL

If you are going to be tracking up here at Castrol Raceway, the S2 box is damn good. I run that one with a torsen diff and it's been great to me. I've also tried the 951 gears and they're ok at Castrol, but not as good as the S2. With under 200 hp, the n/a box is also fantastic on a tight track. 5th gear is useless, but all you really use here is 3rd and 4th.

333pg333

Unless you're running on a track where your terminal speed will be over 150mph...951 5 speed w/ S2 r&p and Guards plate LSD.

Noahs944

Alright,
What about limited slip durability. Is there a style of LSD that doesn't wear out quickly?

333pg333

That's too much of an open ended question. How often is it run? What Trans oil and cooling. How many laps per session. How much mechanical grip will put stress back into it?

Droops83

+1

To help answer some of these questions, I would call Matt at Guard Transmission. For my street/track car I chose the simplest route, which was to rebuild my 951's factory 40/40 LSD with upgraded friction plates and thrust washers, and it works great and has held up well for about 5 years of occasional track use. GT has more aggressive setups available, plus different ramps for 40/60, 50/80, etc, plus their own billet LSD. It all depends on intended usage and how much you want to spend (for the record, I can't remember what my LSD parts cost, it was too long ago!).

Noahs944

Thank you for your replies gentlemen.
My original intent was to order a trans with oem lsd, get it rebuilt than shipped to me.
I'd determined Kevin Gross or Dimi at Flying Horse would be very valuable for this endeavour.
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In the mean time I contacted Lartsparts & agreed to purchase a used open diff S2 transmission from him.
He's driven it and assures me it's in fine condition... so this will at least give me something to drive until I really can afford to buy my dream trans.
The S2 appeals to me (in theory) for my favourite type of driving and simplicity of no cooler.
Plus in colder weather the cooler isn't going to help it shift easier me thinks.
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The 944 S AGR (oem lsd) that I have in my car right now might find it's way into the S2 some day.
Though I've heard friction disks are hard to find.

Droops83

The trans cooler doesn't do much during street driving, but it does come into play during aggressive driving/track use with a LSD trans. The slipping LSD clutches transfer a great amount of heat to the gear oil, so a cooler is a good thing. Also, the cooler doesn't add much "complexity" besides the cooling loop being in the way while servicing the right side axle or shock absorber. I know that it does interfere with some rear coilover shocks, but not my inverted Ground control versions. You could also convert to a conventional radiator-style cooler if need be.

User 41221

Noahs944

Droops83,

You strike me as someone who can intelligently talk about driving into depths well deeper than I am capable of understanding, so respectfully I propose this question to you and others in hopes of expanding my knowledge:
Can you use Left Foot Braking with an open diff in RWD to come close to the performance of a LSD?