PSportoVeloce

I bought a 5-speed S4 yesterday, my first 928 (first transaxle Porsche in fact), and after having driven it for 400+ miles, I've concluded that the 3.09 the PO installed is too short for my tastes. I know 3.09s are very hard to find and the acceleration is hilariously rapid. Anyone want to trade me your LSD or have other suggestions for how to get a taller gearbox (as I understand it, I'd swap the entire gearbox, right?)? I think 2.20 is probably too tall but a 2.73 sounds nice. Car is in San Francisco.

Thanks,

Derek

FredR

Derek,

As I understand the 3.09 is not a Porsche piece of kit but an aftermarket conversion. No idea how many were sold but somewhat few I suspect.

Such might be of interest to a track car given few circuits [if any] will ever see a 928 max out in 5th even with a 2.73.

I would think 3.09 is a hoot to drive in a short circuit 928- it would be interesting to see what Mark K thinks about such.

Good luck.

Rgds

Fred

Mongo

Who made those 3.09s? I was looking for that ring and pinion a while back. Man this thread came up at the wrong time.

Rob Edwards

Doing an auto to 5-speed conversion, Andy?

Mongo

Sorry - I missed that it was a 5-speed. Going to get more coffee now - cost of being up since 4AM

john gill

WHat gearbox type is it ?

mark kibort

Fred, you know ive been dong this a long time and have raced the 2.75 ,, 2.72 many times as well as my stock 2.2.

there is NO hoot beyond 1st gear. (and you end with your ears ringing at 80mph, at unusually high rpm in 5th with a 3.09, because you are stuck in a "s4 stock 4th gear near 3.2:1 if you are runing a 3.09 in 5th on the hyway )

interesing, besides 1st gear, a 3.09 is very close to the same exact ratios as a stock S4, but no 5th and then a super low 1st gear (near unusuable)
I also drive a 12:1 1st gear street car... its only use is in traffic and its easier on the clutch on starts vs our S4 2.2:1 gear box that has about a 8:1 1st

this all means, at any race track , the gears you actua/ly use are near the same. the spacing stays the same too. Basically you know have a S4 , 4 speed with a super low 1st. now , with the 3.09, 2nd becomes the first gear at 8:1, and the rest of the gears match up all the way through 4th (5th)
on a track, the fastest i have ever gone is 156 , three times a lap at Road america. and thats in 4th gear just tapping the rev limiter. (3.2:1 ratio 4th gear)

remember, gears do not make HP they only optimize what you have for the speed range you are operating in.
On the track, you have a super low first 12.5:1 with a 3.09 , like what is found in an austin martin, you never use it but in the paddock . 2nd through 5th are now almost idenical to 1st through 4th with a stock S4 2.2 gear box. so I fail how that on a track would give anything but the identical experience on the track, long or short!

by the way, to the OP.... ive driven the 928 for many many hours in the hills of SF.. there is no issue. in fact, it is MUCH easier to get up the hills due to the fantastic cluch system than an aston Martin with the same hp and the equiviliant to the S4 with a 3.09. (as a note here). for all practical differences, the 2.72 first and 2.2 fist are not as much different as the "2.22 vs 2.72" might indicate. remember the gear ratos of the layshaft and main gears are different. in reality, they are only slightly different. 10% different. from 0 to 55 vs (or 50mph with a 2.72), its not a big change. at 5-10mph , its even less of a difference to feel.

Mongo

And this is why I want a C5 Corvette 4L60E transaxle with 3.90 gearing..... ain't nothing to argue about with that one as no one really knows what it's like.

FBIII

I think there was a 5 speed GTS from western PA that had a 3.09 final drive.

mark kibort

Andy, if you watch some of my races.. there has been a couple of C5s racing T56s with some low rear end and you can see when they shift vs me, but no automatics. an auto like the 4L60E is another ball of wax all together with that 3.90 final drive.

mark kibort

And that is the one i usually refer too. it is so close to an S4, you cant even believe it. almost identical gears to a 2.2 USA 928 5 speed. the ONLY difference is that you have a super low 1st and it becomes an identical G28-11 with no 5th gear in all other ways. a lot of folks get a little confused driving one, when 2nd is really your same 1st as in a 2.2 S4 so they feel like its so much faster, but the truth is, nothing changes past 1st, which you dont use often anyway , and never at the track.

Kevin in Atlanta

I think that was the late Scott Mohr's. And it was also supercharged. Would spin the tires in third gear from a standing start.

mark kibort

since 3rd gear with a 3.09 is really 2nd gear with a 2.2... thats not that hard to imagine. Probably had a after market clutch though, right?

FBIII

Delete

FBIII

Great memory Kevin. Went to his estate auction. Can't remember what became of the car.