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How wrong can a G50 gearbox be?


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I decided to take apart of my G50.00 and see what's going wrong with it, it was 'just some grinding gears' sort of things...

First thing opened the side cover, the diff is quite dead. So I guess it's going to be very bad. Ring gear is quite worn out too, So a new output shaft with new ring /pinion gear + diff set would be the starting point. I think I also need a pinion depth setting tool, see whether I can modified something out of a universal pinion tool.

MEJYSX_o.jpeg MEJYXM_o.jpeg

 

Took the rear casing out, 5th and R gear seems alright, but that as far as my luck goes.

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A special puller is needed to take the 5th gear out. So picked up a vintage puller from a local antique shop, cut/polished the claw until it's thin enough to go between gear and the middle casing. I was told it's going to be a hard pull, but not really. Seems like if the puller shape is correct that's not too bad with the help of a heat gun. The puller did get destroyed after the pull, I guess I made it too thin.

MEJYQN_o.jpeg  MEJYQF_o.jpeg MEJYQI_o.jpeg

Took the 5th/R gear set, synchro and centre casing out. The 1st/2nd is a bit of difficult job. I think I suppose to take the gear holder out first and then pull the gear out on a vice. But I feel like its safer to pull the gear out first with the holder still in place. This was a hard pull, There are 2 races in the 1st gear, one for the bearing and one locked the gear. I cant find a way to pull them separately, eventually I bought a 15 ton puller for the job. Once the first gear out, 2nd & synchro is a lot easier.

MEJZM3_o.jpeg

 

The 2nd gear synchro ring was in bad shape, worn from the side not the top. Seems like something related to the clutch fork / fork shaft bearing / throwout bearing. I guess the clutch wasn't disengaged completely and resulting this, but I might be wrong. Judging from the fact that the ring still has the pointy top, I started to believe that steel ring with different angle may actually be better than brass ring. But I guess at this point I'll still go for brass ring. The dog teeth on the 2nd gear and sleeve was rounded due to the ring failure as expected, so new gear set and sleeve would be needed.

MEJYQ2_o.jpeg MEJYQ8_o.jpeg MEJYQ6_o.jpeg  MEJYQ5_o.jpeg MEJYQ3_o.jpeg

 

Finally get the gear holder out from the bell housing, some more bad news here, the output shaft bearing failed too, possible due the the worn diff / ring gear, they generate vibration and eaten up the bearing, or the other way around.

MEJYPE_o.jpegMEJYPB_o.jpegMEJYP7_o.jpeg

At this point the price for part list is approaching £5000 I guess, consider I paid £12000 for the car (cheapest 911 3.2 on ebay at the time, well, cheap for a reason). Seems like going for a used G50 box would be a better option than rebuilding this. But I still need to get the 3rd/4th gear out to see how bad it is and make the final decision. Also, G50 does seems quite tolerable with worn parts. I mean I drove some car has worse shift than this, but the condition inside the gearbox turns out to be not as bad.

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Posted (edited)

Agreed - great write up. Do you have any idea how it ended up that way? You may find this useful 

 

Edited by Roy M
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Very interesting, a subject close to my heart :angry: Keep the updates coming.

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Posted (edited)
54 minutes ago, Roy M said:

Agreed - great write up. Do you have any idea how it ended up that way?

10 pervious owners should be the main reason. I guess somebody did a money shift once.

It's 130k mile still with its original clutch.. In fact everything was original except one side of the front wing, so the car may be in an accident but no record, but that shouldn't related to the gearbox problem.

The clutch pressure plate has about 1.5mm left, but the clutch fork shaft was eaten by the needle bearing quite a bit, and the throwout bearing was quite loose. When the car in rest in neutral I saw the gear lever shake a bit, so I guess clutch doesn't disengage properly, that's part of the reason if not the main cause of this. From what I can see, the gearbox has been like this for a while before I picked it up, and some metal debris get in between the synchro ring and the gear cone, resulting the ring doesn't sit properly when engaging. The inner side and back side of the ring seems to have a coat of black stuff, not sure its some kind of coating from factory or just metal debris 'cooked' into the brass surface. Also there was some black residual inside the gearbox everywhere, so I guess it may be overheated once, or the transmission fluid gone bad or something.

 

The bottom line is, it has some problem for a while and never been treated properly. All things mixed together and the end result is like this.

That the what the 1st / 2nd synchro ring looks like now. some of the 'black coating' is washable with 'pink stuff' kitchen cleaner, so its less likely to be factory coating. If someone can show me a brand new G50 synchro ring that'll be great.

 

MEKET8_o.jpeg MEKETA_o.jpeg

Edited by sazabi2001
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1 hour ago, Roy M said:

You may find this useful 

 

That post is one of the key source of information I had. I have been researching it for quite a while. But he got a different problem and different way to sorting things out. TBH, not a lot of information about working with G50 on the internet, especially G50.00 from 87-89.

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54 minutes ago, Phill said:

Very interesting, a subject close to my heart :angry: Keep the updates coming.

Update would be slow. From the day I opened the diff cover plate to what you see now has been almost 3 month.

 

I can only take 1 thing out every 1-2 weeks. Not a lot of information about G50.00 is one problem. I have the Bentley manual, but it doesn't have the G50 section, I have the 964 manual its different with G50.00 in some key things, like the location of race and thrust washer. Another thing is I don't have the full access of VW / Porsche tool, so I have to find a way around it. Everything I take something out I need new tool, either I wait for ebay shipping it from outside UK or I modify it out of something. I mean I spent more time on tools rather than the dissembling the gearbox right now.

 

MEKFZC_o.jpeg

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11 hours ago, sazabi2001 said:

That post is one of the key source of information I had. I have been researching it for quite a while. But he got a different problem and different way to sorting things out. TBH, not a lot of information about working with G50 on the internet, especially G50.00 from 87-89.

Agreed. Loadsa 915 but not a lot of IB G50. I’ll be bookmarking this one. 

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This is a really interesting read and would be a great resource for others, so please do keep posting 👏

It's amazing how shagged a gearbox can be and keep working.

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