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G31 1st gear synchro
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twt  



Joined: 19 Dec 2002
Posts: 20
Location: Singapore

PostPosted: Thu Mar 01, 2007 4:49 pm    Post subject: G31 1st gear synchro Reply with quote

Hi,

I noticed that the PET states that the G31.03 transmission used in the 924CGT uses a different synchro ring for the first gear (915-302-301-06) which happens to be cheaper and instock than the one for the G31.01 used in the 924 Turbo (931-302-301-02). Given that the 924CGT is newer and more powerful, I'm incline to think that the synchro ring would be better as a replacement, assuming it will fit. Are there any differences btw the 2 transmissions?

Does anyone have any thoughts on this?
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Rasta Monsta  



Joined: 12 Jul 2006
Posts: 11343
Location: PacNW

PostPosted: Fri Mar 02, 2007 3:29 am    Post subject: Reply with quote

That is a fascinating question. Here is what PET says for 1st Gear Synchronizer Ring:

  • In 1985 PET, it is pictured as Part 47
  • For Turbo tranny (G31.01, G31.02), part number is 931 302 301 02
  • For GT tranny (G31.03), part number is 915 302 301 06
  • There is NO similar part split for free or stationary 1st gears, nor any split for 1st/Reverse guide sleeve, nor for ANY OTHER gearset component

Taken together, this seems to indicate that the 915 part should fit. It is listed in stock through PCNA Atlanta at $84.89.

This is worth investigating further! Great post, twt.
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emoore924  



Joined: 13 Apr 2004
Posts: 2788

PostPosted: Fri Mar 02, 2007 4:24 am    Post subject: Reply with quote

For porsche part #'s, that trailing 2-digit number usually indicates a version, generation or supercession number on the same part. Since they both share 915 302 301, the 06 is the same part number as the 02, just 4 versions further "improved" by Porsche. Talk to a good Porsche parts person and he/she can tell you for sure wether this was true in this case. Based on the same part number being used, my guess would be yes.
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Rasta Monsta  



Joined: 12 Jul 2006
Posts: 11343
Location: PacNW

PostPosted: Fri Mar 02, 2007 4:29 am    Post subject: Reply with quote

emoore924 wrote:
Since they both share 915 302 301. . .


They don't, the Turbo lists a 931 part number.
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-nick  



Joined: 16 Nov 2002
Posts: 2700
Location: Cambridge, MA

PostPosted: Fri Mar 02, 2007 8:51 am    Post subject: Reply with quote

I'd talk to powerhausII. When I talked to them a few years ago they had just gone through a CGT trans and mentioned that it was interestingly different than the stock 931 unit.

I believe that Partwerks of Chicago was selling/doing some kind of conversion to use the 915 1st gear syncro in the stock 931 box. Last I heard, their reputation was soured by lots of bad deals. I have no idea if they're even still in business.

I highly doubt that the 915 will fit right in. If that was the case, then the folks at powerhausII would have known it when I called them up for trans parts. They've seen lots of 915's and have done a great job for me of chasing 931 trans parts.
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1991 964 C4 Cabriolet
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Rasta Monsta  



Joined: 12 Jul 2006
Posts: 11343
Location: PacNW

PostPosted: Fri Mar 02, 2007 9:01 am    Post subject: Reply with quote

Check out the PET, man. The bearings, forks, case, final drive might be different, but the gearsets look the same except for that one part. . .

Not to argue, BTW, I just think its flippin interesting.
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emoore924  



Joined: 13 Apr 2004
Posts: 2788

PostPosted: Sat Mar 03, 2007 4:33 am    Post subject: Reply with quote

Quote:
They don't, the Turbo lists a 931 part number


Uh, yup, never mind, my syslexdia musta be kickin in.
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938GTNick  



Joined: 17 Nov 2006
Posts: 10
Location: UK

PostPosted: Sat Mar 03, 2007 11:12 am    Post subject: Reply with quote

The 924 CGT used the 911 synchro for better shifts from cold.

3rd, 4th and 5th gears plus the pinion head are shot blasted (if anyone can explain why this improves the wear pattern I would be interested to know) and have different part nos to the Turbo:

Gear Set/ G31.01/ G31.03
3rd/ 477 302 903/ 477 302 903A
4th/ 477 302 904/ 477 302 904A
5th/ 477 302 905A/ 477 302 905B
Ring/Pinion/ 931 302 911 01/ 931 302 911 33

Everything else- case, ratios, forks are the same.

Except one spring......
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endwrench  



Joined: 07 Dec 2002
Posts: 1629
Location: Victor, Montana

PostPosted: Sat Mar 03, 2007 5:00 pm    Post subject: Reply with quote

938GTNick wrote:

3rd, 4th and 5th gears plus the pinion head are shot blasted (if anyone can explain why this improves the wear pattern I would be interested to know) ..


Shot blasting "peens" over any imperfections, hairline surface cracks and sharp edges. It also creates microscopic "dimples" that help hold lubricant. This is the theory I was taught.

Todd
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"simsport" said....superchargers are better than turbos its official!....
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ideola  



Joined: 01 Oct 2004
Posts: 15486
Location: Woodstock IL

PostPosted: Tue Oct 07, 2008 3:00 am    Post subject: Reply with quote

This topic is worth resurrecting. Anybody find out any more info on this?
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Dutch924-racer  



Joined: 23 Jul 2007
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Location: The Netherlands

PostPosted: Wed Nov 19, 2008 6:25 am    Post subject: Reply with quote

nobody ?
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Dutch924-racer  



Joined: 23 Jul 2007
Posts: 993
Location: The Netherlands

PostPosted: Tue Jan 13, 2009 5:59 am    Post subject: Reply with quote

Has anybody tried this ?
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ideola  



Joined: 01 Oct 2004
Posts: 15486
Location: Woodstock IL

PostPosted: Tue May 05, 2009 3:37 am    Post subject: Reply with quote

Time for the periodic bump...

Anybody???
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Power Tryp  



Joined: 16 Apr 2009
Posts: 427
Location: Calgary, Alberta

PostPosted: Wed May 06, 2009 3:53 am    Post subject: Reply with quote

Any one know if that part is still in stock? If it is then I'll see if I can pick one up from my local guy. Just so you know though I'm not dropping my transmission till winter rolls around so it'll be a while till you hear results.

Tryp
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v8carreragts  



Joined: 05 Sep 2003
Posts: 661
Location: Tucson, AZ

PostPosted: Fri May 08, 2009 1:18 pm    Post subject: Reply with quote

I'm sure it will fit. If you look in the factory turbo manual and the factory early 911 manual (w/915) the dimensions are the same and the turbo manual states that it is "same as 915." The Carrera GT transaxle is identical to the G31/01 (ROW) except for the first gear synchro ring and shot peened gear sets.

The GTS/GTR has some parts that are very different.
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