Bill Verburg

Here's something similar to what you are doing I modified the trans to what you have, except for the really low `1st I think you will be happy

the engine is a 993 RSR spec, rev limit 7500, in a 2900# RS/CS chassis in low drag config,, hp is 301 at the rear wheels at 7200

changing 1st is a really expensive proposition, you have to change the trans main shaft


all the internals should be upgraded to at least /31 spec, /30 would be better, the street cars have plastic bearing shells which certainly need to be replaced, shift forks iare another priority item, none of this is cheap, a routine rebuild on my /30 was close to $7k 5 years ago

do spend the money on an asymmetric lsd a GT or factory motorsport would be the way to go here, 40/60 these thigs are magic compared to the old symmetrics

Maxi_z

Ok did not know what was required to replace first gear but was expecting something not that simple and more expensive than just a gear change.

What do you think about the Quaife ATB differential?

I would also for sure choose a plate differential if the car main use was track , and I already know how they work, but maybe they could be better than the oem 964 optional old LSD ?

I used a quaife ATB on a Lotus exige 380 Cup tuned to 430 bhp and even on track with semi slicks it was working well and I Europe I could buy one for 1200 usd

Thanks

Bill Verburg

lsd's are two edged swords, which is why they have always been optional except on some performance models, the primary danger is when you hit a totally slick patch at speed, the higher the lock the worse the outcome

the gear type generally work well but only on acceleration, another plus is that they don't add much to the thermal load

the plate type work well on both acceleration and deceleration the asymmetric more so

having a high lock on decel allows more rear brake bias which raises the efficiency and effectiveness of the brakes

I have a 40/40 plate type w/ a bit higher than usual preload in my '76 hotrod and a Porsche Motorsport 40/60 in my 993, Both cars have 993RS brakes which have way more rear bias than the typical 964, Thes lsds are essential to the most efficient braking so I love the asymmetric plate types

Your use will vary

Foxman

I rebuilt the transmission in my 964 a few seasons ago. I wish I had installed steel synchros. Never an issue in the street, but when the car gets heated up on the track I get locked out of second gear at times when downshifting. Turn four at Palmer is a typical location. It’s downright dangerous in traffic in our older 911’s.

From my perspective, that second gear synchro is the most important one and worth the money.