Engin

I was watching the thread and as I do have some problems with my gearbox, I may do the same when I pull it out.

However, Dave has the same car as mine, a '90 C4. Therefore, an LSD is not an option and G50 ratios may not apply. However, all ratios are in Adrian's book, which I do not have with me at the moment.

I understand that Ruf can pack a 6-speed into the original box, is this correct?

RSAErick

Whoa! Those are some expensive options. As I have stated in a previous topic, I had the opportunity to take a track ride in a fellow's RS America last summer. I believe that he only had the final drive ratio changed.... although I could be wrong. I felt that the difference was enormous, and the experience left me wanting some of that. The differences in 3rd and 4th gears were most notably improved (at Pacific Raceways in Seattle).

So it appears that there are two options for modifying the gearing of the 5-speed G50:
1. Change individual gears.
2. Change the final drive ratio

Option #1 sounds impressively expensive. Does anyone know what Option #2 would cost? What are the advantages and disadvantages of each?

Also, I am quickly burning through my syncros.... although I've slowed my shifts down considerably to prolong their life. If I was to do any tranny mods, I would REALLY like to add steel syncros. What on earth makes them so much more expensive than brass?

Hopefully someone can chime in with some clarification.

Thanks.

Erick

Christer

Dave

I think you will find that the 0-80 range is not where the main benefit lies with changing the ratios or installing a 6 speed. Indeed, if I remember, the 6 speed 993 box has pretty much the same top speeds in the first 2 gears as ours (so that's 70mph or so out of the way then). Where the 6 speed starts to makes sense is the mid-gears so from 70 upwards as someone else has said.

If you had really short gears 1-4 say - so that 4th gear maxed out at 80mph - of course the acceleration in each gear would be brutal but you would lose time with all the gearchanges. So if you had to change gears say 3 times to get to 80mph the overall time might not be that impressive because you would have spent valuable time whilst changing gears. Obviously I am exaggerating slightly, but if a car that doesn't make 60 in 2nd gear races one that does then the lower geared car needs to make up the time it takes to make a gear an additional change. There has to be a balance in other words.

I think the 6 speed box is a good idea though, and if I didn't have a small mortgage's worth of plans for the car already, it would be on my list. In fact, I may have just added it but will I ever get that far?

Steve Weiner-Rennsport Systems

If I might add some opinions on this subject,......

Installing close-ratio gears is kind of an "infinite" subject; one chooses the particular ratios to match the mission as its not a one-size-fits all. There are MANY choices here.

This really improves the 0-60, 0-100, and 60-top speed acceleration and its akin to adding 50 HP to the performance envelope of the car.

The only known drawbacks are reduced top speeds and reduced bank balances.

Installing lower ring & pinion gears does nothing to address the real problem here; the stock ratios are way too far apart for maximum performance and a lower R&P only shifts the problem around a bit. Its like squeezing balloons,......you simply transfer one problem from one place to another.

Given how people actually drive these cars, we always install the Factory Motorsport steel syncros since they outlast the stock brass ones, 3:1. They are not cheap and there is only one source for them; Porsche Motorsports. If one likes to shift "briskly", these steel syncros are truly cost effective to install, given the labor to keep changing the brass ones when they wear out,....(fast).

Ruairidh

Steve - are you able to give any ballpark estimates here - you'll see from earlier posts the guesses are around $600-$1000 per gear and $1000-ish for the labor so around $3-4000. Is that a reasonable starting point if one is thinking about this? Accepting, as ever with these kinds of quotes that YMMV.

Thanks

Steve Weiner-Rennsport Systems

Ruairidh:

As you can imagine, there are many variables at work here in each case so all I can do is offer some guidelines.

G-50 gears range from $ 800 to $ 1000 depending on ratio and whether they are factory or aftermarket; we use both.

An LSD is another variable; factory or Guard Transmission.

Steel syncros run $ 2100 for a 6-speed, slightly less for the 5-speed. Some people want billet shift forks, too.

Until its disassembled & inspected, one cannot tell if you need a operating sleeve or two, or not.

Labor rates vary nationwide, but we get 12 hours total to overhaul the G-50.

Lastly, if these transmissions are done correctly, they can be pretty bulletproof,.....

Ruairidh

Thanks Steve, I appreciate the guidelines.

mj964

If you can tolerate the financial pain, I think this is a great mod for the 964. I had it done two winters ago and wish I had done it sooner. I thought the ~165 mph advertised top end was useless marketing bs in the US; better to give up some top end and go with closer ratios. We replaced 3-4-5 and left the final drive alone. I second Tom W's experience - gearsets w/ steel synchros were about $1000 each, bringing the total with R/R labor and other misc. stuff to something over $5000.

I had the work done by Jerry Pellegrino and the guys at European Performance here in the Boston area. I remember Jerry's opinion at the time was that it's "like adding 100 hp" in the range where you'll do virtually all your driving, and doesn't involve engine internals or reliability issues. In fact, the car drives much better around town and pulls so much better through 3rd and 4th. Jerry did caution that no replacement gearsets will ever be quite as smooth and quiet as the Porsche originals. I did notice slightly more gearbox noise, but we removed the intermediate muffler and that seemed to cure the problem.

Mike
'91 C4
Boston

Tom W

Just add the LWF at the same time as the gear change and you will not have to worry about gear noise. On a 993 the LWF makes the transmission sound like a cement truck. My gears had a bit of a high pitched whine that went away after a few hunder miles. FWIW, my transmission was done at Rothsport, the folks Steve is associated with. I'm very happy with the final product (and looking for an excuse to do it to the 964 that my wife might believe).

Mike: what ratios did you end up with and why did you not do 2nd?

Anatol

I had a G50 20 sixspeeder installed two years ago. Initially I was very satisfied compared to the long gearing of the Swiss 964-box.
However, being the long US- or second version of the sixspeeder, I found that second and third were way to long for the mountain roads in my area.
Currently I am considering changing ring and pinion from 9x31 to 8x32. This would reduce the top speed from 313 km/h to a more sensible 270.
But, as has been pointed out already, the spacing between the gears would not improve. And it is quite an investment.
Beware of the G50 21 gearbox, though. It is prone to third gear failure and may need frequent repair work if used accordingly.
I am also considering changing to steel synchros for third and fourth gear at this occasion because I experience baulking and grinding noises when I shift swiftly. But this will kill the piggy bank, given the crazy labour rates here in Switzerland.

DaveK

Well, I must admit - I've pretty much been scared off this idea by the costs. But I did mail BS Motorsport and they said :

Individual ratios average £350 - £500 each. Changing the final drive would be about £1500. Plus 10 hours / £500 in labour and a gasket set. So I guess changing the final drive would be about £2.5K plus vat.

tonytaylor

I installed a 993 RS G50/32 6-speed in my car. It has close ratios, (3.154,2.000,1.522,1.241,1.031,0.829) steel syncros on all gears, all ratios interchangable, motorsport LSD and reinforced shifter internals. Reading the above I`m beginning to feel a bit pleased with myself as in retrospect it was a bit of a bargain. I believe these are sometimes still available from motorsport teams, especially in Germany and are well worth the effort of finding.

Randall G.

Per Bruce A.'s book, here are the gear ratios/final drives for some 964/993 transmissions:

US 964 G50/05:

I = 3.500
II = 2.059
III = 1.407
IV = 1.086
V = 0.868

Final drive = 3.333

US 993 6-speed G50/20

I = 3.818
II = 2.048
III = 1.407
IV = 1.118
V = 0.921
VI = 0.775

Final drive = 3.444

RS Euro (also Swiss, as I recall) G50/10 5-speed

I = 3.154
II = 1.895
III = 1.407
IV = 1.086
V = 0.868

Final drive = 3.444

Euro (early) 993 6-speed G50/21

I = 3.818
II = 2.150
III = 1.560
IV = 1.242
V = 1.027
VI = 0.820

Final drive = 3.444

Randall G.

Reading Adrian's book, looks like I recalled wrong on the Swiss version of the G50. Yes, they share the same final drive and first/second gears, but are different thereafter. According to Adrian's book:

5-speed G50/04 (Switzerland)

I = 3.154
II = 1.895
III = 1.333
IV = 1.029
V = 0.868

Final drive = 3.444

Also, Bruce A.'s book lists the US G50/05 as having a final drive of 3.333, Adrian's book shows it as having a final drive of 3.444. Bruce's book is a misprint--all of my literature shows the US C2 as having a 3.444 final drive.

A few more points while I'm at it. Bruce's book calls the G50/03 a Euro transmission, the G50/05 a US transmission. But, they have the same gear ratios and final drive, once you get past the G50/05's misrepresented final drive. Adrian's book says the G50/03 is ROW/USA (Switzerland exc.), and the G50/05 USA from '92.

RSAErick

Great info on this topic! Thanks for all of the contributions!!!

Now if only I could win the lottery....

Erick