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What is the best tranny to use for these exotic builds

I thought I would start a thread to provide a place to compile info for all with links to builds and conversions for transmissions used for these builds. I just realized that even with the meager test build I did I may be at the ragged edge of what a 915 may be able to take without mods. So give your thoughts and please provide links to conversions and builds so we can all see how it is done. Lets see if we can make a thread that would make it into the pelican wiki when it comes on line and the ultimate thread also.
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Old 03-05-2010, 06:05 AM
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In a 915 car a 76/7 930 short transmission is the easiest.

The other 4 spd 930 transmissions can be fitted to but it ether has to be shortened or the motor moved back I believe.

The gear drop with the 930 transmissions is about 2800rpm (at about 50mph) out of first and about 1800 on the later gears. They are geared for almost 200mph.

Many put a G50 5 speed from a 87-89 or 90-94. They have lower gears that a turbo and make for a fast street car. One builder highly recommends a reinforced side plate mod to keep them togeather.

I believe the NA 5 speeds are geared for up to about 160mph with rpm drop of about 2800 (at just under 40mph), 1900, 1350. 1350 rpm drops.

The grand daddy of turbo transmissions it the G50/50 five speed from the 91-93 turbo. First gear is tall and the gears are still a bit wide. 2nd through 5th can be changed but first is part of the main shaft so changing that is not easy. Keeping first and regearing this as a close ration box could be a lot of fun. Geared for up to almost 200mph.

Any of the G50's have to be shortened and or the torsion tube (78-89) modified to fit.

Not sure about the 6 speeds as this will typically require cutting the torsion tube center section our and doing some significant modification.

Not a transmission expert so I do not know the smaller details of any change overs.

Last edited by 911st; 03-06-2010 at 08:00 AM..
Old 03-05-2010, 06:53 AM
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Not to be pedantic, but the G50/50 was only for the 1989 930, so made for one year. The 91 and up 964 Turbos had a G50/52, which had the same ratios as the G50/50, but i'm led to believe the 50/50 is stronger? Not sure why, or even whether that is true? But in most respects the 50/50 and 50/52 are the same.

Lots of info here Welcome to Rennsport Systems, Porsche Performance Products for the 21st Century

Here are the codes and ratios for the other boxes

930 ’76-‘88
1st 2.25 overall 9.50
2nd 1.30 overall 5.51
3rd 0.89 overall 3.77
4th 0.63 overall 2.64
final 4.22

G50/50/52 ’89-‘94
1st 3.15 overall 10.84
2nd 1.79 overall 6.16
3rd 1.27 overall 4.37
4th 0.97 overall 3.34
5th 0.76 overall 2.61
final 3.44

G64/51 ’95-’98
1st 3.82 overall 13.14
2nd 2.15 overall 7.40
3rd 1.56 overall 5.37
4th 1.21 overall 4.16
5th 0.97 overall 3.34
6th 0.75 overall 2.58
final 3.44

G96/50 ’01-present
1st 3.82 overall 13.14
2nd 2.06 overall 7.09
3rd 1.41 overall 4.85
4th 1.12 overall 3.85
5th 0.92 overall 3.16
6th 0.75 overall 2.55
final 3.44

GT3 street car G96/90 ’99-present
1st 3.82 overall 13.14
2nd 2.15 overall 7.40
3rd 1.56 overall 5.37
4th 1.21 overall 4.16
5th 0.97 overall 3.34
6th 0.82 overall 2.82
final 3.44

930 4 speed 930/30-33 ’76-’77 “early” (rod shift)
930 4 speed 930/34-36 ’78-’88 “late” (rod shift)
930 5 speed G50/50 ’89 only (rod shift)
965 5 speed G50/52 ’91-’94 (rod shift)
993 6 speed G64/51 ’95-’98 Twin Turbo (rod shift)
996 6 speed G96/50 ’01 to present Twin Turbo (cable shift)
GT2/GT3/R/RS/CUP* (rod shift up to ’98, cable shift ’98 and on)
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87 930, 993 turbo engine, RS Tuning 520PS/515lbf-ft, Arrow Rods, ARP hardware, Solid lifters, G50-50, RS Flywheel, 890nm Sachs clutch, RSR coil overs all round, 993 C4 calipers front, 930 fronts on the rear, Ruf Speedlines.....
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Old 03-05-2010, 07:03 AM
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J, thanks for the correction.

ps: for turbos a limited slip differential is pretty much demanded.

The 930's have a pretty good friction style set at about 40%.

The 91-94 G50 turbo transmission has something like a 40% under acceleration and 80% on deceleration to moderate throttle lift over-steer. For autoX it can make the car push a little more.

Most the NA G50's do not have a limited slip so you will have to budget for this. There were some with LSD and they must work but one source noted they were not a great unit for what it is worth.

With any friction LSD they are a ware idem and may lose some of there effectiveness with use.

Again, not a transmission expert.
Old 03-05-2010, 07:16 AM
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This is a good start lets keep going, need some links to conversions that have been done.
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Old 03-05-2010, 07:29 AM
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The 930 4 speed was the only turbo box to come with an 'option' for a LSD, all the 5 speed turbo boxes came with them as standard
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87 930, 993 turbo engine, RS Tuning 520PS/515lbf-ft, Arrow Rods, ARP hardware, Solid lifters, G50-50, RS Flywheel, 890nm Sachs clutch, RSR coil overs all round, 993 C4 calipers front, 930 fronts on the rear, Ruf Speedlines.....
Old 540 BMW, XB12S Modified, for being a total hooligan
Old 03-05-2010, 07:59 AM
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The G50/50 in the '89 930 has lower gears than the G50/52 of the 964T. I do not know the ratios but sure you can find them.
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Old 03-05-2010, 09:21 AM
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Brian you still have a 915 right? What did you do to beef it up?
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" Porsche there is no substitute" I always liked that saying. Air cooled is the only way to go!
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76 Blazer also restored by me
Old 03-05-2010, 09:24 AM
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Quote:
Originally Posted by RarlyL8 View Post
The G50/50 in the '89 930 has lower gears than the G50/52 of the 964T. I do not know the ratios but sure you can find them.
The ratios are identical Brian, exactly the same for both boxes
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87 930, 993 turbo engine, RS Tuning 520PS/515lbf-ft, Arrow Rods, ARP hardware, Solid lifters, G50-50, RS Flywheel, 890nm Sachs clutch, RSR coil overs all round, 993 C4 calipers front, 930 fronts on the rear, Ruf Speedlines.....
Old 540 BMW, XB12S Modified, for being a total hooligan
Old 03-05-2010, 09:49 AM
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A client who has both '89 930 and '91 964T reports they are not the same ratio, the 930 being lower geared. He purchased both cars new so ratios are stock. That is my one data point as I am not a transmission guy.

Yes I use a 915 with my modest HP engine. I have built 2 boxes using WEVO bearing retainer and late model side plate cover. If not abused or tracked the tranny will last. I damaged the shims on one tranny drag racing. The second tranny has custom 4th and 5th gears for the highway. First is too low unless you like to auto-x and then is perfect. 2nd gear will haze the 315 tires with 300WHP. With 350WHP 2nd will roast and 3rd gear will haze. Stupid quick in 1-3 gears. With 400WHP the tranny will break at will.
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'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
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Last edited by RarlyL8; 03-05-2010 at 10:28 AM..
Old 03-05-2010, 10:21 AM
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It'll feel lower geared down to the tire sizes, internally the gearboxes are the same ratios. I only know because i've done so much research. I'm way less of an expert on pretty much every subject
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87 930, 993 turbo engine, RS Tuning 520PS/515lbf-ft, Arrow Rods, ARP hardware, Solid lifters, G50-50, RS Flywheel, 890nm Sachs clutch, RSR coil overs all round, 993 C4 calipers front, 930 fronts on the rear, Ruf Speedlines.....
Old 540 BMW, XB12S Modified, for being a total hooligan
Old 03-05-2010, 10:44 AM
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Quote:
Originally Posted by RarlyL8 View Post
A client who has both '89 930 and '91 964T reports they are not the same ratio, the 930 being lower geared. He purchased both cars new so ratios are stock. That is my one data point as I am not a transmission guy.

Yes I use a 915 with my modest HP engine. I have built 2 boxes using WEVO bearing retainer and late model side plate cover. If not abused or tracked the tranny will last. I damaged the shims on one tranny drag racing. The second tranny has custom 4th and 5th gears for the highway. First is too low unless you like to auto-x and then is perfect. 2nd gear will haze the 315 tires with 300WHP. With 350WHP 2nd will roast and 3rd gear will haze. Stupid quick in 1-3 gears. With 400WHP the tranny will break at will.
Please give me some details of the build (parts used, gears and such)and limits I think my build will not exceed 400 hp on the 3.2 I think and I may just break down my 915 and build it up with strong parts I rebuilt it in 83 with all new bearings and syncros and it only has 40K roughly on it since the rebuild.
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" Porsche there is no substitute" I always liked that saying. Air cooled is the only way to go!
76 911 C.R.A.P. Gruppe #2 BIG time TURBO C.R.A.P. Bitz EFI/EDIS Now MegaSquirt 3
76 Blazer also restored by me
Old 03-05-2010, 11:01 AM
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This is some good stuff here I know I will be able to make an intelligent decision on what tranny to use in the future. I like the idea of a tranny geared to 200 mph I have had my tranny to 150+ (speedo pegged) and plenty left in the throttle. I hope someone has some links to conversion threads to earlier model 911's that would make this thread complete. I am searching as we speak to find some to add.
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76 Blazer also restored by me
Old 03-05-2010, 11:08 AM
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In my opinion converting to a G50 is the best upgrade I've made. Running a G5001 with billet side cover, never a problem and it gets abused. If you like top end use a G5050 or 52. I do have everything for another G50 conversion if your interested.
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Old 03-05-2010, 11:22 AM
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Can you take a pic of all the stuff required to do the conversion and post it?
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" Porsche there is no substitute" I always liked that saying. Air cooled is the only way to go!
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76 Blazer also restored by me
Old 03-05-2010, 11:24 AM
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Quote:
It'll feel lower geared down to the tire sizes, internally the gearboxes are the same ratios.
That is a possibility. I should have stated in the original post where the info came from as it is hearsay; although from an owner of both machines.

I use the 915 but cannot recommend it as each person has different driving habits. You absolutely cannot beat on the 915 or it WILL fail. This takes some enjoyment out of the driving experience if you are a person who likes drag race starts and speed shifting. I find that neither will help me get down the road faster so I let the engine do the work. The tires break when boost hits which is presumed to be less shock than a drag start.
Both of my 915s have the same mods, WEVO bearing retainer and late model (Carrera) side plate. Another mod that will further protect the tranny is an LSD. This will distribute the "punch in the nuts" that boost gives the side plate equally to both sides.
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Old 03-05-2010, 12:25 PM
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Some conversion threads I found

This one is one we all Know the link starts where he gets his tranny
3.9 RSR project --- my Carrera reborn

Britains project
1969 912 Turbo Project Update.

G50 into a 89
Fitting 6 speed G50 to '89 Carrera

915 into early car with 901 tranny
1971 911T Transmission Conversion

Link to body motions tranny upgrades
http://www.bodymotion.com/Core/911_transmission_upgrades.htm

Putting a G50 into a 78 sc
Putting a G-50 into a 78'SC - Where are pic's?

The Wevo stuff for 915
WEVO - pics of components for shifter and internal gate

Pros and Cons of converting
Pros & Cons opinions per G50 in old 930

This one is Johns intresting approach to putting in a G50
Verify a G50 is shortened?

These are the structural mods Tre did for Jack
Calling all structural reinforcement experts.

Well thats all I could find for now I will keep looking.
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" Porsche there is no substitute" I always liked that saying. Air cooled is the only way to go!
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76 Blazer also restored by me

Last edited by gsmith660; 03-05-2010 at 01:28 PM.. Reason: added more links
Old 03-05-2010, 12:34 PM
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Here's the majority of the parts needed for a conversion.

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Old 03-05-2010, 11:27 PM
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Thanks
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76 Blazer also restored by me
Old 03-06-2010, 05:14 AM
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Lite 75,

Is that keeping the G50 full length?

Could go with coil over springs in the rear. Would not need the spring plates or inside torsion bar adaptors. Might be able to just notch the 915 torque tube but do not know for sure.
Old 03-06-2010, 07:58 AM
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