D666S

Hi!! Happy New Year first of all

Title says it all. I will have to change/rebuilt my clucht/lsd/gearbox in the near future, have some strange noises (apart from a brutal amount of kilometers ) so start to think in an upgrade. Track use will be more intensive in the future as well so...

... my first thought was to go for a 964/993 RS gearbox but seems quite impossible to find one.

Second, go for a 993 6-speed gearbox but seems to have very similar ratios to those of my standard 964.

and finally, kind of a crazy option, go for a sequential (cluchtless) gearbox but I can't imagine which one of where to find out. (Comments on Ruf EKS gearbox are not very good).

Really appreciate your opinions guys!!

Thanks a lot,

Best,

David

Geoffrey

All of the 964 gearboxes are essentially the same. Slightly different ratios in 1 & 2 and different R&P, but the end result is the same that the gears used 3-5 are too long. The 993 gearbox is essentially a 964 gearbox with an additional gear for an even lower cruise RPM. So, any gearbox will need shorter gears for performance.

For your gearbox, I would suggest buying a 996 Cup LSD (they are inexpensive), selecting a 5th gear ratio the same as your current 4th and buying a new 2-3-4 gear set with proper spacing. That will give you about 3600rpm in 5th gear at 75mph, but will keep the engine in its powerband much better.

Bill Verburg

Your usage will determine your gearing, a track only car will likely be be geared much lower that a street only car, dual use somewhere in the middle

Here's a summary of the oem g50s, normalized w/ the same tires and rpm for comparison purposes,



Each has it's advantages for specific situations;

I like a tall 1st - the 6spd /3x are the best for that followed by the 5 spds but if you live in very hilly country the low 1st in a /2X might appeal to you

For a dual use car I like a top of ~160 -170mph, that gives reasonable cruise milage and noise, you certainly won't be using the full top end in most places but it is a very good indicator of cruising rpm/milage, I certainly woudn't want anything less than ~160, but others my like the /21, low 1 top of ~150 in 5 then you have the 171mph 6th for highway use.

The factory did a decent job of spreading the rest of the gears between 1 and top.

The /3x series are all(except the /30) available though Porsche dealers as rebuilt trans w/ a factory waranty(probably the others too, but I didn't research that). The /3x include stronger internals like steel synros ans a better lsd

NineMeister

I drive a lot of aircooled cars, and the very first difference that I notice when jumping out of a 964 and into a 993 is the gearchange, for some reason or another the 993 is just way sweeter than the 964 and is why I would have no hesitation in recommending a G50/21 993 six speed for your 964.

You are correct, you will not find a decent 993RS gearbox anywhere nowadays, so the option for the future would be to re-gear the G50/21 as and when funds permit. I fully understand where Geoffrey and Bill are coming from with respect to ratio choice on track, but any close short ratio box will really compromise the economy of the car on the road hence the overdrive 6th has to be a priority given the cost of fuel in Europe. I particularly like the tall 1st gear of the RS (993 & 964) so if you were to re-gear I would go for a 25mph spacing between the gears, giving something like 45/70/95/120mph from 1st/2nd/3rd/4th with a 150mph 5th and 180mph 6th.

demonfish

whats an approximate cost on that setup colin? i have a standard C2 box, and its on my list of upgrades along with an LSD... Would it give more noticable acceleration?

kurquhart

Last I checked (about 6 months ago), rebuilt G50/31 were available (two in stock) from the factory for about $8k. While there were no G50/32 in stock at that time, they were expected soon (i.e. not NLA) and priced around $13k. Are you saying that they are now NLA?

Cupcar

When I bought my G50/32 a few years ago, and ordered it for the $8K price Porsche quoted initially, Porsche refused the order stating that they meant $8K to rebuild a G50/32 and the price for a whole new gearbox was really $13K .

Tom W

I bought a G50/32 for my 964 last year. The price delivered from Germany without a core-exchange was $15k. They refuse to accept a 5-speed housing as an equivalent for the core exchange so you'll get stuck paying that additional fee to upgrade.

I've also had my 993 6-speed re-geared years ago (shorter ratios through 5th and convert the stock 5th to 6th gear). The shorter ratios are more fun on the street in addition to nicer on the track. To re-gear the 993 transmission was roughly $1k per gear to be changed and the mainshaft had to be changed too (stock main shaft had 2nd splined onto it).

Geoffrey

That is just stupid money (15k) for a 6speed gearbox...especially since the gearing isn't ideal. I'd rather get a 5 or 6spd core and regear it, add a good LSD, steel syncros, steel shift fork and be done with it.

kurquhart

The quotes I got (e.g. G-Box, Patrick Motorsports) to regear a G50/20 with steel syncros, Guard LSD, and external cooler was about the same money ($14k). Obviously, if you have the skill/tools/time to do it yourself, it can be done a lot cheaper.

Geoffrey

Call Joel Reiser, he can do it for much less.

Jeff Lamb

Bill, thanks for attaching the great reference information showing all of the gear sets. This is very helpful. In your research, did you find any information on the stock gear sets used in the G-50/52 box?

Thanks,
Jeff

Tom W

Geoffrey makes a good point. Yes, it's a stupid amount of money. At the time the work was in-process, we were unable to find a good donor case and rather than wait and potentially miss race dates, I opted to simply buy one from Porsche. We'd all want our upgrades to be as cheap as possible, but we sometimes need to make compromises.

FWIW, my though process went something like this ...

I decided to change transmissions because I just got tired of working hard to catch up to the competition only to have them pull away from me in a couple turns where 2nd (in the 5-speed) was too low and 3rd was too high. So, given the decision to re-gear, I had to decide what ratios to use. I spent a lot of time looking at my Traqmate data for the rpm at corner entry, mid-corner and corner exit at the tracks I drive most often in trying to determine what ratios I should use in a 5-speed re-gear job or switching to a 6-speed. The /32 was pretty close to what it appeared I needed. Having actually used the new configuration for a year, the /32 is sub-optimal but it workes better than what I had (speeds change when you remove 300+ lbs from the car). There are a few occasions where there just isn't enough track left before the braking zone to take the .8 seconds to shift to the next gear. What I do is simply keep the foot to the floor beyond the normal shift point (6500) as I can rev to 7400 without issue. It's a compromise, but it works. I normally only use 2-5th so a 5-speed could have been employed if I wanted a top speed of about 135 or 140. I decided I wanted more (a 6th gear) that will be used when I get to the higher speed tracks on the west coast (Portland or Cal Speedway for example). The 6th isn't needed at Laguna Seca, Sears Point, Buttonwillow or Thunderhill. It's a decision I made before selecting the box for reasons I was comfortable with. Before anyone goes out and spends silly amounts of money on a transmission, they should clearly understand the compromises they are making and be comfortable with the rationale behind them. Cheaper would have been nicer, but I'm very happy with the car that I've had built and the choices made.

Tom W

Jeff: I've not seen a G50/52 referenced anywhere.

A G50/50 is a 5-speed with 3.15, 1.789, 1.269, 0.967 & 0.756.
A G50/54 is a 6-speed with 3.154, 2.000, 1.440, 1.133, 0.969 & 0.828

Geoffrey

A G50/52 gearbox is much longer than either the 5 or 6 speed gearbox. In fact, a good upgrade for a 91-94 C2 turbo is to replace the G50/52 gears with ones from a N/A gearbox.