G50 Ring and pinion -

[ZCAT3]

I believe the G50 runs a 9:31 ring and pinion. If I want a little taller gearing would going to a 9:36 make sense? Does anyone know where these can be had? Also, are there any online calculators for looking at gearing changes? Thanks.

[Carrera3.5L]

Yes, the 3.2L Carrera ratio is 3.44:1. Porsche AG makes a couple of "sport" ratios, an 8:32 (4.00:1) being the most "popular".

Andial sells these, but they are not cheap. Last I checked they were about $2,500. Factory quality but you pay for it!

David Brown in England as well as Hor Technologie in Germany both make final drives for various Porsche applications but am not sure that they have any ratios available for the G50.

Ralph

EDIT: I just reread your question, these sport ratios aren't taller but actually shorter. The 8:32 is 14% shorter then stock which means faster acceleration around town but with a loss of top speed (if that is important to you). The other ratio that Porsche offers is 26% shorter, which will be WAY to short for street use. PM me if you would like the Porsche part numbers for either of the above.

[Geary]

Yes, a slightly taller 3.33 (9:30) ratio R&P is available for these. They are $700-1,000 for good used.

Factory 8:32 's are around $2,200 from vendors other than Andial.

Forget the DB R&Ps for the G50 series, as these have been problematic.

[350HP930]

Bill, by 'taller' gearing do you mean changing the R&P so the engine runs at a lower RPM?

As the above answers show there is alternative gearing available to go either way but the ratio change you mention is shorter, not taller.

[ZCAT3]

Thanks guys - yes, what I want to do is increase top speed in each gear.

Based on some rough calcuations this is what I come up with based on the 7200 RPM rev limiter in my 930 and the stock G50 and 930 gearing:

930 4 speed

1: 55 mph
2: 95
3: 140
4: 206

So first is taller than I thought. At 75 in 4th you would be about 2650 RPM.

Compare this to the stock G50 -

1: 43 mph
2: 74
3: 108
4: 136
5: 174

At 75 MPH in 5th, you would be at about 3100 RPM.

I would like to ideally make 1st and 5th taller. But if I do that it seems like I should do all the gears.

Paul - how much of a change does the 9:30 ring and pinion make?

P.S. JWE will be doing the rebuild. Thanks for the referral.

[Carrera3.5L]

I got a couple of PM's asking for the numbers, so I'll just list all of the Porsche part numbers in case anyone else may be interested:

950 302 911 06 - 9:30 or 3.333:1

950 302 911 05 - 9:31 or 3.444:1

950 302 911 22 - 8:32 or 4.000:1

950 302 911 23 - 8:37 or 4.625:1

The 3.333 is 3% taller then the stock 3.444. If you give me the tire size that you are running I can calculate a gear chart for you.

Ralph

[ZCAT3]

That would be very helpful Ralph. I am running 295/30 18s in the rear. Thanks.

[Carrera3.5L]

Hi Bill,

I guess I should have asked you too what G50 5-speed box you were referring to. I was/am assuming that you are talking about the G50/01 used in the 3.2L Carrera. The G50/03 used in the C2 has the same 1-3, but with a little taller 4th and 5th. The turbo 5-speed is completely different from 1-5 then the normally aspirated models.

Let's just assume we are comparing using the 3.2L Carrera transaxle. I can always go back and rework the numbers if you intend to use the C2 or turbo versions.

1st is 3.500
2nd is 2.059
3rd is 1.409
4th is 1.125
5th is 0.889 (I have conflicting info with 5th, as my notes show a 0.892 but the Bentley states 0.889)

Using the tire size you gave, here are the speeds at 7,000 rpm in each gear with the stock 3.444 ring & pinion:

1st is 43.14 mph
2nd is 73.33 mph
3rd is 107.16 mph
4th is 134.21 mph
5th is 169.83 mph

Changing just the final drive to the slightly taller 3.333 yields the following:

1st is 44.57 mph
2nd is 75.77 mph
3rd is 110.72 mph
4th is 138.68 mph
5th is 175.49 mph

Going the other way (shorter) with the 4.000 final drive gives the following:

1st is 37.14 mph
2nd is 63.14 mph
3rd is 92.26 mph
4th is 115.55 mph
5th is 146.23 mph

Let me know if you need any more details.

Ralph

[ZCAT3]

Ralph - I am using the G50/01 as you guessed. I would actually like even higher gearing than the 3.333 yields, but that definitely is an improvement. Using my 7200 rev limiter cutoff with your numbers I get this:

1: 46
2: 78
3: 114
4: 142
5: 180 (with 3000 RPM being 75 MPH)

I was working through this last night to determine what I thought would be ideal gearing for the way the car is used - motly street with maybe a DE here and there. For street driving the biggest concern is starting from a stop and freeway cruising (so 1st and 5th). For DEs of course it is gearing for the various tracks we may visit. Most of the tracks we go to are fairly tight technical tracks (Laguna, Infineon, Thunderhill, Buttonwillow) with the exception being Willow Springs. At the four technical tracks, there really is no place where we would get over 140 - maybe Thunderhill is my driving skills advance sufficiently. So having 4th gear be able to accomodate 140 is probably sufficient. At Willow shifting to 5th on the front straight is not difficult - I reached about 155 there once in a different car.

In any case, what I came up with for ideal gearing was the following:

45 in 1st
80 in 2nd
115 in 3rd
145 in 4th
200 in 5th
would be ideal.

So the 3.333 gets me really close with the exception of 5th.

[350HP930]

I am not exactly sure what you want to achieve from this slight gearing change, but one thing it will do is reduce your ability to accelerate in each gear.

IMHO you are headed in the wrong direction if you want to make yourself faster from a dead stop and at the track.

If its a couple of your shift points you are unhappy with you need to focus on changing your individual gear sets instead of the R&P but thats a bit more $$$.

[ZCAT3]

I am not looking for a drag car or stoplight racer. My car was setup to optimize the 4 speed and it did that very well. The car puts out 405 RWHP and 440 RWTQ - boost starts as low as 1300 RPM. Given this, the G50 gearing is actually quite short for the car. I am tempted to just leave it alone, or maybe only change 5th, but as it is the tires are slipping under even fairly mild throttle (and these are 295/30 18s).

[350HP930]

Ah, well if you currently have more torque than the tires will handle then ignore my post.

I was assuming that you had a NA 911 and were just working on making yourself slower.

What turbo are you using by the way? I would love to see boost as low as 1300 rpms.

[ZCAT3]

It's a K27 7200 - probably the same turbo you have. My car is maxing it out though. It doesn;t even hold .9 bar above 5000 RPM. By the time I am at peak power it is barely at .8 bar. I would need to have it modified to a K27 HF format in order for my HP to exceed the torque number. So I am probably leaving 30-50 HP on the table, but I am rarely at full throttle above 5500 anyway.

[350HP930]

I had the 7006 which trades the bottom end boost for top.

When it all goes back together I will be sporting a garrett GT37.

[ZCAT3]

Looks like a sweet project. I think I am still good for another 30 - 50 RWHP even with CIS, so I think you can hit your mark. I have the Euro CIS system and did have the fuel head flowed for better fueling. This made a big difference on the AF ratio.