Gary R.

Raised/altered spindles are illegal in PCA stock so may as well gear away!

flatsics

If your trans must come apart for a rebuild, ideally you would do both. If you have to choose one or the other I would re-gear now and add the LSD later.
You will be told that you have to take the trans apart again to install the LSD.
I have installed 20 or so LSD's over the years and have never had a problem with transferring the shim stack over to the new LSD and checking the engagement. Never had a problem with the pre-load on the bearings. Most of the transmissions have hundreds of track hours with no problems.
I have always used a stock ZF or preferably a Guards unit, so I can't speak to the other type of diffs.
I did one of the first GT diffs in the 996 (according to Paul Guard at the time) and Porsche did not sell shims for the 996. The manual stated to swap shims to the new unit if replacing the LSD.

A properly re-geared trans should make a bigger difference in lap time, vs. just the LSD.
If your trans does not need rebuilt, then I would just do the LSD now.

Re-gearing the trans and changing the splits between gears will really change the car.
It is much different than a R&P change or smaller wheels tires.
The 15" wheels used for PCA stock have several advantages, not just gearing change. I would argue that the lowered ride height with out compromising the suspension geometry, less unsprung weight and rotational mass are more of a benefit than the gearing change.
Adding an LSD is more of a subtle change. I am not trying to say that a LSD is not a good thing, because it is. With a 911 and its rearward weight bias the main benefit of an LSD is under deceleration. Makes the car feel much more planted and secure. But it is a feel thing and a 911 can be driven very quickly without a LSD. Just think of how many crappy stock LSD's are out there-- they stop working after about ten track hours--if that.

flatsics

Current thread on Pelican

http://forums.pelicanparts.com/porsc...g50-3-2-a.html

Astroman

FWIW, that has been my experience as well.

My friend Chris and I often co-drive enduros together. At the last race, we drove his car. Our cars are similarly prepared E class 911s except mine has an LSD and his doesn't. I was exactly 1.0 second slower in his car... which was more likely car comfort and car preservation than anything. I could certainly tell a difference but it wasn't a huge issue.

Cory M

Good point on the additional labor to open up the trans twice versus just bolting in and setting up the lsd later on, probably a lot cheaper to do the gears now if the trans is already apart

IcemanG17

LSD all day.......better gearing only helps assuming you can use it getting off the corners better...without LSD, your backpedalling....

flatsics

That might be true in with a 928, but just isn't the case with a moderately powered 911.

sig_a

"The 15" wheels used for PCA stock have several advantages, not just gearing change. I would argue that the lowered ride height with out compromising the suspension geometry, less unsprung weight and rotational mass are more of a benefit than the gearing change.
Adding an LSD is more of a subtle change. I am not trying to say that a LSD is not a good thing, because it is. With a 911 and its rearward weight bias the main benefit of an LSD is under deceleration. Makes the car feel much more planted and secure. But it is a feel thing and a 911 can be driven very quickly without a LSD. Just think of how many crappy stock LSD's are out there-- they stop working after about ten track hours--if that.
__________________
Doug Crossman

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I often switch from taller 17's to shorter 15's, although the 15's are stock Fuchs at 8" wide. So width limited rear tire traction is aided by lower chassis, less unsprung weight and Kaaz Super Q LSD with max lock on acceleration set to 80 percent and max lock on deceleration set to 100 percent. It is a "reversed" 1.5 type LSD factory set for 911's only. The reverse configuration reduces understeer on power and increases lock on coast. Japanese manufacturers name asymmetrical LSD's "1.5".

Snap-shot of my G50 limited slip installation procedure. Special tool at narrow end of case locks pinion in place while dial indicator measures thru final drive cover for exact fit.

analogmike

He's got a stock 3.2 engine, not a race engine, so it's not peaky. He can probably keep it in one gear for a long time while making good power. It would be very different for, say, a hot rod 2.0 liter 911 vintage engine which has no torque down low.

KaiB

Given the comments above I've reconsidered my opinion somewhat (i.e., waffle).

Braking under the LSD is indeed improved, it's actually wonderful...but if you feel stable enough now, then I will have to admit the the short tranny (mine is short 2,3,4 and 5) is huge as a performance enhancer.

In medium length straights, say from 2d to 4th, I easily get three car lengths if not more over other 964s due to the tranny alone. It is fact that during the early summer before I came up to speed I could run even laps with far better drivers (i.e. 2 to3 secs a lap) only because I could accelerate better.

I do like the idea of somehow doing both if you could somehow swing it, but if not, and if you have no intention of running PCA stock or prep...the tranny change will get you across the line faster.

embacpa

i see mention of 275/35/15. does anyone on hear actually have that setup on a carrera 3.2. i really want to go that route, but am worried it won't fit. i have elephant racing 23/31 tb's, sport shocks, and the works. it is lower than stock. how can i know if it will fit?

many thanks

Gary R.

Evan, on here as "Der ABT" does, PM him.

mehoff

Thanks to all that responded, great feedback and much appreciated. After spending weeks going through gear ratios, corresponding top speeds and numerous wheel/tire and potential R&P combinations, it turns out my decision was made for me. The SoCal POC runs primarily at moderate to high speed tracks, and while the gears would be benefitial, it would cut my top speed by about 10 mph at Cal Sppedway, so no go until I have a "fake" stock engine that can rev up to 7k.

Just put the rebuilt tranny in today, steel race syncros, new inards......and the Guard LSD. We'll see.

38D

Therein lies the issue. Unless you are going to change the gears for every track, it will be sub-optimal at least at some tracks. Its true of the factory ratios and true of custom ratios too.