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Beartooth
Joined: 05 Apr 2022
Posts: 257
Location: Roberts, MT
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 Posted: Tue Apr 30, 2024 3:18 pm Post subject: |
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I emailed both EBS and CMS; I didn't hear anything from EBS, but CMS got back to me promptly and seemed pretty helpful. Their response:
"Hi William, thank you for contacting us. Low gear grinds are common and synchros and synchro teeth are available. But 1st/reverse shift sleeve not which certainly ups the difficulty level if needed – and its very likely. Estimate attached for what we can provide. LMK what else is needed after you open and inspect the gearbox."
So I probably have a major missing puzzle piece in the 1st gear shift sleeve; hopefully I don't get stuck digging for the best used one I can find... It looks like I'd be at $1800 for the parts they have - that's including the 2nd/3rd wear items (syncros, shift sleeve, and dog rings). I think I understand the dog rings - those are splined to the gear with teeth on the outer end, and together with the syncro and shift sleeve form the engagement mechanism, correct? It's just that on other transmissions I've messed with, those are either integral or maybe pressed onto the gear.
The good news is, I drove it recently, and I couldn't make 3rd-5th misbehave, so I may not need much outside of first and second gear. And of course that's the hard part (1st gear anyway); pretty frustrating that Porsche couldn't address those NLA parts. I'm going to make an effort though - even if it means throwing a bunch of money at having it repaired (assuming that's even an option). Although it's driveable, it really is a drag to work around in stop-and-go. At least there doesn't seem to be too much more to address; I'll just have to see, but I might get away with just a synchro on 2nd. With care, I can always get 2nd without a problem, but I really have to be careful with the upshift.
Anyway, I hope I'm not thread-jacking too much here! It definitely seems like CMS will be good to work with. It's too bad about the 1st/reverse shift sleeve; I'm guessing the precious few NOS sleeves on someone's shelf either aren't likely to come out, or they'd cost more than the price for a decent used box (not that those are easy to find!).
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1980 931 diamond in the rough |
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chuck21401
Joined: 20 Feb 2005
Posts: 561
Location: Annapolis, MD
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| Posted: Fri May 10, 2024 11:29 pm Post subject: |
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| Beartooth wrote: | | Low gear grinds are common and synchros and synchro teeth are available. But 1st/reverse shift sleeve not which certainly ups the difficulty level if needed – and its very likely. |
Some good news on the horizon. Catellus Engineering doing a run of the 1st/reverse shift sleeve part. Timeline is the next couple of months. The euro G31 that I'm having rebuilt is disassembled and I'll wait until the new part is ready. Will post more details about my rebuild in a different thread. Sorry to thread jack but thought you all might want know.
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1981 Porsche 931 w/S1 engine & g31 transmission. Water-cooled intercooler |
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Beartooth
Joined: 05 Apr 2022
Posts: 257
Location: Roberts, MT
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| Posted: Sat May 11, 2024 4:38 am Post subject: |
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That's good news; it jibes with a follow-up email from CMS that mentioned a reproduction may be in the works. No thread-jack at all because it seems the first gear parts are the most needed and the most lacking components for the G31. Based on other posts, I'm betting hundreds of rebuildable G31s have been scrapped because first gear got trashed and the parts couldn't be found, probably at any cost. I'm sure the price will hurt (the 2nd/3rd sleeve was quoted at $467; I'd think a small run of 1st/rev sleeves would be significantly more), but it'll be great if we have the option. The good news is, I might be able to slip in under $1000 for the other parts I need, but of course that's just an optimistic guess until I get it apart. So here's hoping that materializes and we're able to fully repair our 'boxes. I can only imagine how much a solid gearbox and shift linkage will transform my driving experience!
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1980 931 diamond in the rough |
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Cedric
Joined: 27 Aug 2004
Posts: 2721
Location: Sweden
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| Posted: Sat May 11, 2024 4:59 am Post subject: |
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| Beartooth wrote: | | That's good news; it jibes with a follow-up email from CMS that mentioned a reproduction may be in the works. No thread-jack at all because it seems the first gear parts are the most needed and the most lacking components for the G31. Based on other posts, I'm betting hundreds of rebuildable G31s have been scrapped because first gear got trashed and the parts couldn't be found, probably at any cost. I'm sure the price will hurt (the 2nd/3rd sleeve was quoted at $467; I'd think a small run of 1st/rev sleeves would be significantly more), but it'll be great if we have the option. The good news is, I might be able to slip in under $1000 for the other parts I need, but of course that's just an optimistic guess until I get it apart. So here's hoping that materializes and we're able to fully repair our 'boxes. I can only imagine how much a solid gearbox and shift linkage will transform my driving experience! |
I bought parts in 2012, looking back at ideolas old site the first gear dogring costed 230usd, and the syncro 115. Different times:) CMS made them back then, somehow they made it designed to rotate backwards and i had to sendit back to cali for a new one, should be sorted by now 
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1980 924 Turbo
www.instagram.com/garagecedric/ |
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kevingross
Joined: 15 Apr 2015
Posts: 35
Location: Stow, MA, USA
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| Posted: Thu May 16, 2024 12:07 am Post subject: |
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| Cedric wrote: | | I bought parts in 2012, looking back at ideolas old site the first gear dogring costed 230usd, and the syncro 115. Different times:) CMS made them back then, somehow they made it designed to rotate backwards and i had to sendit back to cali for a new one, should be sorted by now |
CMS still has the 1st gear dog rings (engagement teeth). They don't rotate backwards: the asymmetry is in the tooth profile. It is opposite the asymmetry Porsche / Getrag introduced at some point in the type 915 transmission 1st gear dog ring. Cheers,
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Kevin
Catellus Engineering, Inc.
http://www.catellusengineering.com/
catelluseng@gmail.com |
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chuck21401
Joined: 20 Feb 2005
Posts: 561
Location: Annapolis, MD
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| Posted: Tue Jul 30, 2024 6:57 am Post subject: |
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| Beartooth wrote: | | I'm betting hundreds of rebuildable G31s have been scrapped because first gear got trashed and the parts couldn't be found, probably at any cost. |
I'm starting to think that the 79/80 931 with the G31 should be avoided altogether. The price of a transaxle rebuild could easily exceed the value of the car. Ask me how I know.
On hindsight it probably would have been less expensive to convert to the later Audi 5 speed along with the parts necessary for the conversion.
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1981 Porsche 931 w/S1 engine & g31 transmission. Water-cooled intercooler |
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Beartooth
Joined: 05 Apr 2022
Posts: 257
Location: Roberts, MT
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| Posted: Sun Aug 04, 2024 8:14 am Post subject: |
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| chuck21401 wrote: | | Beartooth wrote: | | I'm betting hundreds of rebuildable G31s have been scrapped because first gear got trashed and the parts couldn't be found, probably at any cost. |
I'm starting to think that the 79/80 931 with the G31 should be avoided altogether. The price of a transaxle rebuild could easily exceed the value of the car. Ask me how I know.
On hindsight it probably would have been less expensive to convert to the later Audi 5 speed along with the parts necessary for the conversion. |
I guess it depends on one's expectations and the car in question. Mine gearbox is tricky, but pretty manageable if driven carefully. So, an otherwise nice car with the same issues would still be worth something as a driver even with no hope of repair. I didn't get a quote on a full rebuild; I'd think $5-8k though. I don't have a great picture of values, but it seems like $10k for a decent, fully-functional driver is about right, and $20k for a pristine low-mile car is in the ballpark. Obviously, on many cars (like mine), coupled with enough minor problems or one or two other big ones, that's going to drive the value into parts car territory - fixing one up would be a labor of love - and that's a tough thing to get through to most sellers, especially on a car that looks nice and drives.
If you've got a decent car with typical G31 issues, or are looking at one that's priced right, it's probably worth it in the long run to invest in. Both the prices of 911s and the growing rarity of the 924 in general will help, and I could see the 931 with the "real Porsche" gearbox becoming the holy grail of 924s (leaving aside the GTS). Of course, the circumstances where it's going to pay off in the short run are limited, but even in the worst case, you're not going to be selling one for less than it cost to have the transmission done - unless we're talking about a car that's an obviously poor choice to begin with. That said, if one had access to a parts car to do the Audi swap, that would make a lot of sense. I've thought of it myself, but unless something popped up locally, I'd probably be spending as much to get all the parts I need in my hands than it'd cost to fix what I've got.
Anyway, I tend to see gold where there is no glitter (and sometimes I err), but I see the G31 931 as a real gem. The dogleg first and "real Porsche" gearbox are "eye of the beholder" things, but it's often those little things that make all the difference. If I were a betting man, I'd bet on the 931/G31 being worth investing in. But ultimately, it's a very personal thing: if the dogleg "real Porsche" gearbox just seems like fluff, there's no reason to be married to it. On the other hand, if the idea of going to the Audi box seems like a let-down and you're not taking out a second mortgage for it, stick with the G31. No right or wrong answers here.
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1980 931 diamond in the rough |
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Fifty50Plus
Joined: 28 Feb 2008
Posts: 1400
Location: Washington DC area
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| Posted: Sun Aug 04, 2024 12:22 pm Post subject: |
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I'm a big fan of the snail shell gearbox. I raced a '72 911 where 5th was way far off to the right and up. Sold it and got a 924 race car with the Audi trans. Hated it and built a '79 924 with the snailshell. Fifth is where I think it should be for a race car rather than somewhere near the passenger side windshield area.
Good to hear that folks think the 931 with the snail shell is an up and coming Porsche like the 911. I have three 931's aging gracefully on my buddy Matti's back 40. 
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1979 924 NA race car
1982 924 NA race car - Sold
1982 924 Turbo almost a PoS
1981 924 Turbo a real PoS, new engine
1982 924 Turbo nice body, blown engine
1972 911 E race car - going to Vintage
Various 944s to become IT-S race car |
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chuck21401
Joined: 20 Feb 2005
Posts: 561
Location: Annapolis, MD
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| Posted: Sun Aug 04, 2024 11:21 pm Post subject: |
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| Beartooth wrote: |
I guess it depends on one's expectations and the car in question. Mine gearbox is tricky, but pretty manageable if driven carefully. So, an otherwise nice car with the same issues would still be worth something as a driver even with no hope of repair. I didn't get a quote on a full rebuild; I'd think $5-8k though. I don't have a great picture of values, but it seems like $10k for a decent, fully-functional driver is about right, and $20k for a pristine low-mile car is in the ballpark. Obviously, on many cars (like mine), coupled with enough minor problems or one or two other big ones, that's going to drive the value into parts car territory - fixing one up would be a labor of love - and that's a tough thing to get through to most sellers, especially on a car that looks nice and drives.
If you've got a decent car with typical G31 issues, or are looking at one that's priced right, it's probably worth it in the long run to invest in. Both the prices of 911s and the growing rarity of the 924 in general will help, and I could see the 931 with the "real Porsche" gearbox becoming the holy grail of 924s (leaving aside the GTS). Of course, the circumstances where it's going to pay off in the short run are limited, but even in the worst case, you're not going to be selling one for less than it cost to have the transmission done - unless we're talking about a car that's an obviously poor choice to begin with. That said, if one had access to a parts car to do the Audi swap, that would make a lot of sense. I've thought of it myself, but unless something popped up locally, I'd probably be spending as much to get all the parts I need in my hands than it'd cost to fix what I've got.
Anyway, I tend to see gold where there is no glitter (and sometimes I err), but I see the G31 931 as a real gem. The dogleg first and "real Porsche" gearbox are "eye of the beholder" things, but it's often those little things that make all the difference. If I were a betting man, I'd bet on the 931/G31 being worth investing in. But ultimately, it's a very personal thing: if the dogleg "real Porsche" gearbox just seems like fluff, there's no reason to be married to it. On the other hand, if the idea of going to the Audi box seems like a let-down and you're not taking out a second mortgage for it, stick with the G31. No right or wrong answers here. |
The G31 that is in my car is "manageable if driven carefully." Have to be purposeful in getting it into first gear from a stop, then shift slowly in 2nd or it will grind. 3rd, 4th and 5th work well, but occasionally will nick something while shifting. I like the dogleg 1st, it reminds me of a 911e that I owned years ago. When I bought my 931, I knew that I'd never get back what I put into it...but that I'd probably be spending much less than for a 911SC from the same era.
| Quote: | | I can only imagine how much a solid gearbox and shift linkage will transform my driving experience! |
That's what I'm talking about. I really enjoy driving my car...especially with more boost. The shifting experience is the only thing holding it back.
So I decided to buy another transaxle, this one is a euro G31 (thanks again Fifty50Plus) and have it rebuilt as I continued to drive my car. In my mind I was thinking the cost would be around $5K, but it's going to be a bit more. I'm guessing that there are only a handful of shops that are willing to work on these transaxles and be able to acquire the parts (or reproduce the parts!) necessary to pull it all together.
I've been waiting for the reproduction 1st/reverse shift sleeve part; that is taking longer than expected. But as luck would have it, I found a NOS part offered for sale...now my project can move forward.
Guard Transmission in Colorado posted a bunch of NOS G31 parts for sale back in December 2023 and the 1st/reverse shift sleeve was still available.
I believe the other parts might still be available, here's a link to the post with pics and part numbers if board members are looking for any of these:
https://www.facebook.com/GuardTransmission/posts/pfbid02sQxRdtWUWQgvdsnyrZ3gcE4ma1uADA1EYHQijciLgtgjDf6wkcr6rSPqWZuUUHoYl
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1981 Porsche 931 w/S1 engine & g31 transmission. Water-cooled intercooler
Last edited by chuck21401 on Thu Sep 05, 2024 9:30 am; edited 1 time in total |
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Cedric
Joined: 27 Aug 2004
Posts: 2721
Location: Sweden
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| Posted: Mon Aug 05, 2024 6:09 am Post subject: |
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While on the subject we need to give Magnus rat rod gearbox some words of encouragement, so he keeps his gears on the inside. His G16 n/a dogleg box still lives somehow, with over 500Nm of torque, pretty remarkable what that gearbox and 20mm shaft have done without stripping something. Of course it wont last forever, but still pretty darn crazy what a 70s gearbox for a 125hp car can do
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1980 924 Turbo
www.instagram.com/garagecedric/ |
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chuck21401
Joined: 20 Feb 2005
Posts: 561
Location: Annapolis, MD
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| Posted: Thu Sep 05, 2024 9:24 am Post subject: |
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Today I heard from Kevin at Catellus Engineering that my transaxle is ready. Looking forward to seeing that delivery truck pull into the driveway.
Will start another thread detailing the adventure involved in pulling the existing transaxle and installing this one. I have a feeling that I'll need some guidance from fellow board members. Plan is to put 12" tall cribbing under the wheels (with jack stands for back up). I'm hoping that will be high enough off the ground. The first picture is the completed transaxle on the stand; the second one is from during the assembly process using the CMS bearing retaining plate.
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1981 Porsche 931 w/S1 engine & g31 transmission. Water-cooled intercooler |
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