930 transmission gear source.

[David]

I posted in this question in the 930 rebuild thread, but I realized that thread is in the 911 tech forum. Maybe a moderator can move that thread over here.

I'm thinking about lowering 2nd, 3rd, and 4th gears while I have the engine out for a clutch replacement. Anyone have tips on where to find 930 gearsets?

[sand_man]

Even though I have the factory manuals, the lack of knowledge on what parts to actually buy and replace and where to get them is one reason I'm tempted to let a shop rebuild mine when that time arrives. Being a DIYer to the death, that's hard for me to admit!

I wish someone offered a "rebuild kit" of sorts.

[David]

I know what you mean. I plan to call a few shops first and see what a turn key option will cost me before I break it open. The other reason is my DIY projects seem to take much longer than expected.

[sand_man]

Perhaps we could use this thread to create a project/parts list. Maybe those that have gone through it a time or two - DIY and pro shop - could help identify, at a minimum, what needs to be replaced once you crack open Pandora's box!!! From my perspective, the broken stuff would be obvious, it's the "wear items" (synchros, bearings, bushings, washers, spacers, sliders, springs, etc.) that concern me. I've said it enough times to equal the United States National Debt, but I HATE to go back in!!!!!!

[rsrmike]

I would call Paul Guard @ Guard Transmission.

I've never bought gear sets from him but have installed a few of his Limited slip diffs

VERY knowledgable guy, and was nice to deal with...

[rsrmike]

http://www.guardtransmission.com/

[David]

Thanks.

I also found Powerhaus here: http://www.lightgearsahead.com/

[SCHNELE]

You can call Jim Patrick at Patrick Motorsport, Dave will you be going to upgrade the synchros as well?

[David]

Originally Posted by SCHNELE

You can call Jim Patrick at Patrick Motorsport, Dave will you be going to upgrade the synchros as well?

I might, what's the upgrade?

[Jim2]

I used Powerhouse II about 4 years ago. I've heard they changed hands since then. I bought 2-4 gears, all sycro parts and a gasket kit $4K. I paid a local to do the install so I wasn't experimenting, well worth the $300 for his labor. He said I could have done it myself, but then again I don't feel the need to be inside my 930 box often enough to warrant the learnign curve.

[David]

Another question, which gear ratios?

Here are the two options I'm considering. Option 1 looks good for track use but not so good for the occasional highway trip.

I'm leaning more toward Option 2, but it has as bad a 2-3 jump as stock.

Option 1 gear ratios: 2.250 1.444 1.038 0.767

Option 2 gear ratios: 2.250 1.444 0.963 0.688

[Gino]

old and current 1st- 29:36 or 2.25 (that is stock)... good to 50mph
new 2nd 18:26, or 1.44 (stock is 23:30, or 1.30)... good to 80
new 3rd 26:27, or 1.038 (stock is 28:25, or 0.893)... good to 110
new 4th 29:23, or 0.793 (stock is 32:20, or 0.625)... good to 145
gearsets were $750 each set...

standard LSD - R&P 4.22 ratio... 245-45 tires on 16" fuchs

Very happy with this set-up.

[SCHNELE]

Dave you can use the steel motorsports synchros but you will have to change the operating sleeve assembly as well.

[David]

Originally Posted by Gino

old and current 1st- 29:36 or 2.25 (that is stock)... good to 50mph
new 2nd 18:26, or 1.44 (stock is 23:30, or 1.30)... good to 80
new 3rd 26:27, or 1.038 (stock is 28:25, or 0.893)... good to 110
new 4th 29:23, or 0.793 (stock is 32:20, or 0.625)... good to 145
gearsets were $750 each set...

standard LSD - R&P 4.22 ratio... 245-45 tires on 16" fuchs

Very happy with this set-up.

Do you drive it on the highway? If so, is the higher RPM tolerable?

[Craig 930 RS]

Powerhaus II - great guy to deal with, bought a G50 5th gear set for the 930.
Very helpful and easy to get along with, FWTW.

[SCHNELE]

I thought I would share with you an analysis I did about my car with different gear ratios..You need to keep in mind that when you accelerate within a certain gear, probably the shorter ratios will make you accelerate faster, but in real life, you downshift if you need to, and then you keep pulling longer under torque with a taller gearbox, which puts you ahead, while the other guy is shifting, you are still accelerating..
I have added the ratios of the Supercup gearbox (shorter ratios) for your info..

The typical "RPM drops" argument is not valid, I have yet to see one of these modded cars dropping below the boost threshold when they change gears..The worse you can drop is 3800 RPMs, and you will still have boost there, or it will be there in a fraction of a second. With shorter gears you will also have traction problems, although withe the Guard it should be fine.

All of the above information is true for you since you have a high torque/high HP car. You would wring through short gears way too fast and may also have traction issues from the induced wheel spin. Looks cool but you will lose in the end.

[SCHNELE]

If you are going with a high HP engine, you do not need the close gear
> ratios, it is a mistake. Contrary to common (un) wisdom around these
> forums and with gearbox builders, taller gears on a high HP turbo
> engine will give you better results. This is why I was going to go the
> G50 route.. (I know you are getting the G50/50 and not G50/01 or
> G50/03 which are crap))
>
> The longer you stay in gear and acceleration , the faster you will go.
> On N/A cars with weak torque relatively speaking, it is a different
> story altogether. I have datalogging data proving what I am saying.
> High hp turbos are different.
>
> One of the best compromises for track and street is the 6 speed
> G64/51, except for the shortish 1st gear ratio, the others are
> fantastic. For a strictly street car that wants to beat anything else
> in acceleration, the stock G50/50 is the best.
>
> The 2 fastest 911 turbos (964 3.6 turbo and 993TT) that are today in
> the US and arguably the world, are both using a G50/50 gearbox BUT!
> with stock gears, not short gears. One is running 9.7 seconds at
> 147mph and the other is doing 8+ seconds (recently at 167mph) both are
> street cars. I know both guys.
>
> All of these strong components that Patrick and Guard use are sourced
> from New Zealand and Australia for a fraction of this cost..
>
> I am currently driving a plain stock TT gearbox with my 650 hp engine,
> with a stock differential, and I won the last race I had ahead of 42
> other cars in GT1 in Bahrain (highly modded cars including 996
> Supercups etc).. My car was going all over the place because of the
> stock diff, but the stock 6 speed gearbox is excellent. I have now
> bent my shaft finally, but that was after big abuse to my
> gearbox..(not the one that is in the US of course ) My sequential
> gearbox is waiting for GT2 EVO axles from Germany, since they have a
> larger flange, so it has not been installed yet.
>
> For strictly street, keep your G50, just add a Guard LSD to it. If and
> when you bend the shaft or damage a synchro, then replace it, you will
> see, it will last years
>
> The cost of the sequential? You don't want to know It cost 45,000
> Euros to build, but of course I did not pay that much. This gearbox
> was a one off especially built for Franz Konrad for Le Mans in his
> 993GT2 EVO

quoting Jean@porschespeed.com

[Gino]

David-
yes on hwy. I usually drive at 3000-3400 rpm. must be going 70-75; not really sure. Used to have a modified 240Z back when with a 4.44:1 LSD rear and it was similar short gearing in a 4 spd. the 930 has awesome response; no need to drop down to 3rd as it takes off like a rocket. the beast is modified... all the usual stuff; just under 400 RWHP, 375 TQ.

also, allows me to tool around town in 3rd whereas before I had to be in 2nd.

I'm not draging anyone, but the acceleration leaves you in the back seat from 2-4th. now I need to work on the dip-n-squat...
-Gino

[David]

SCHNELE, I've considered that too, but the spacing did feel really wide even at Texas World Speedway which is a big track.

I got a quote from the only shop near Houston I'd consider doing the work and it was a little over $4K. The price sounds about right, but given the last couple week's financial impacts, I'm thinking this may be something I can put off for a while. I'd sure like to do it now while the engine's out, but now I'm leaning toward just putting in a new clutch and calling it good for now. I can put that $4K toward seats and a rollbar, get some more track time, and make a more educated decision.

[A930Rocket]

Sliders, synchros, dogteeth (1-4) and a gasket set run about $2k. For my track car, 3rd and th are the gears I use the most and thats what wears out. That's the basics and from there you need to look at the bearings, etc.

My trans had been rebuilt and about 1 1/2 years later I needed to rebuild it again from lots of track use. I opted to just replace the above components and it worked fine.

There's a write up here on Pelican. There was another thread here on the 930 forum talking about it. If you take your time you can do it.

http://forums.pelicanparts.com/showthread.php?threadid=255526