LSDs

[Astroman]

Sort of a follow up to my previous transmission thread:

I've found somebody to rebuild my G50 along with a ZF LSD...

First, for a dedicated track car (roll cage), what do you all recommend as the % locking factor?? I've read 80% but the tranny guy I spoke to said 40% is enough and easier to drive. Also, I almost never autocross. Should I stick with 80%??

Second, needless to say, the steel synchros REALLY add to the price... My only problem is grinding when upshifting into 3rd gear... Is it reasonable to replace ONLY the 3rd gear synchro with steel, and the others with the softer OEM stuff??? I'm not trying to be cheap but this is an unexpected rebuild (and I'm not somebody that has more money than I know what to do with)...

Thanks for the suggestions-

[earlyapex]

http://rennsportsystems.com/2d.html

http://www.rennsportsystems.com/1-d.html

Good article from a respected Porsche expert, Steve Weiner.

[cstreit]

80% lockup would definitely be over the top for a street LSD. You'd be leaving black streaks in your driveway and street corner as the wheels skipped during tight slow turns. 40% is certainly acceptable for most situations.

[930LDR]

The Guard LSD that I ordered in February FINALLY came in last week. Had it put in and yesterday but won't be back in the city to test it out until next week. I ended up going with a 40/60 split at numerous peoples recommendation. I hear 50/80 is really the hot setup for the track but as Chris mentioned would be pretty annoying on the street. I'll be back at the track in three weeks and can't wait to see what kind of difference the LSD will make over my open diff.

[KTL]

Keep us posted Rob. Interested to see what kind of time you shave from your typicals.

As far as the original post, i'd forego the steel synchro arrangement. Mine stock brass stuff just started crunching at about 75K miles. I'm sure you'll get PLENTY of life out of new brass parts as long as you: 1. treat the car right and don't abuse with lightning shifting, 2. ensure that the engaging pieces are all replaced so as to have a new interface between all parts that match gear speeds. This is not cheap either.

As long as you're going thru the trouble to rebuild, you'd be wise to get the plasma discs that Guard offers to extend the life of the ZF diff.

[Bill Verburg]

for street 40%, especially if the re-builder is using Paul's plasma coated disks. The % doesn't tell the whole story anyhow. High preloads can send the breakaway torque way up even though the theoretical # is 40%

The ultimate is an asymmetric unit such as the Guard 40/60 or 50/80. W/ them you get the best of both worlds, you want the high # for deceleration, but want the low for cornering

[Astroman]

But fellas, my original question was for a 99.9% track driven club racer!!!... NOT a street car. The only street driving will be to and from my mechanic's shop. I appreciate the replies but all the advice has been for street cars...

The tranny is done and the ZF LSD locking factor was set to 80% per my request... I hope it's good. It'll get re-installed next week... but not back to the track until the end of September...

BTW Kevin, I agree regarding the brass vs steel synchros. But as a compromise between durability and price, I opted to use steel for the 3rd gear synchro only...

[175K911]

Originally Posted by 930LDR

The Guard LSD that I ordered in February FINALLY came in last week. Had it put in and yesterday but won't be back in the city to test it out until next week. I ended up going with a 40/60 split at numerous peoples recommendation. I hear 50/80 is really the hot setup for the track but as Chris mentioned would be pretty annoying on the street. I'll be back at the track in three weeks and can't wait to see what kind of difference the LSD will make over my open diff.

Likewise, got mine 2 weeks ago and waiting to get the car into the shop to install. My experience with my previous 911 was that going from open diff to 80% ZF was good for close to 2 sec per lap at the Glen.

[Astroman]

Originally Posted by 175K911

My experience with my previous 911 was that going from open diff to 80% ZF was good for close to 2 sec per lap at the Glen.

Now that's what I wanted to hear. Thanks!!

[9elf]

I am also running a 80/80 factory ZF. I drive to the track and the mechanic with no problems. On the track it is definately worth more time, probably more under braking (much more stability) than drive out of corners, but time is time.

[930LDR]

I will likely keep the 40/60 setup thru next season and see how I like it. May then pull it out and flip it to the 50/80 setup and see what kind of difference I see.

Can't wait to test this thing out!