G50 Rebuild

[TheMentat]

I've been searching high and low for a thread on rebuilding a G50. The documentation from the workshop and Bentley are silent on the later gearbox, and I'm trying to figure out what is involved, and if anybody around here has ever done it themselves.

Any pointers on threads or documentation to rebuild a G50 box from an '88 car?

[Jeff Alton]

What gone wrong with it Chris?

Cheers

[TheMentat]

It gets ornery at track events. In the latter parts of the day, I cant get half way through a session without third gear giving a significant grind on upshifts. It is definitely related to temperature.

To be fair, I haven't done an event since I replaced the gear oil with Redline (it looked like Royal Purple was in it before). With that in mind, it is likely now a non-issue.

I'm also just plain curious how it's done!

[Porsche944parts]

I have a nice set of gears and a lsd diff available if your interested.

[TheMentat]

Originally Posted by Porsche944parts

I have a nice set of gears and a lsd diff available if your interested.

now that's just plain evil!

And here I was thinking that I'd be less prone to "while I'm in there" reasoning with a tranny rebuild!

[Porsche944parts]

Just offering, Cause I was looking for the same answers and cant find them. I cant figure out how to correctly dissassemble the thing after you get the diff out.

But yea, I will be parting with the insides of the G50 if you need anything pm me. lol.

[KTL]

There is factory documentation on the G50. It's in the later manuals. I have service microfiche for the 87-89 models and it does a fair (I say fair, not good) job of telling you what to do. Also, the 993 manual has information on the G50 repair. The 6 speed of the 993 is of the same design as the 964 or the early G50 from the 87-89 911. I have an electronic copy of the factory manual that was available from a UK site for quite a while. Do a search on the web and i'll bet you'll find it.

dean and cstreit here have done a G50 build. So has John Walker. Ask some questions and i'm sure they'll give you useful feedback.

I have a similar problem on only hot days. This problem is typically worn synchronizer assemblies. I bet if you double-clutch it, the crunch can be avoided. That's what I do when mine gets crunchy near the end of a session. Or you could install an oil cooler........ But that only masks the real problem- synchro replacement needed

[TheMentat]

Originally Posted by KTL

I have a similar problem on only hot days. This problem is typically worn synchronizer assemblies. I bet if you double-clutch it, the crunch can be avoided. That's what I do when mine gets crunchy near the end of a session. Or you could install an oil cooler........ But that only masks the real problem- synchro replacement needed

That's kind of what I feared. Thanks for the info.

[Peter Zimmermann]

Originally Posted by TheMentat

That's kind of what I feared. Thanks for the info.

I have also done G 50 repairs, and can help, if needed, by possibly faxing pages from the factory manual. What you describe is most likely a synchro assembly that's worn sufficiently to cause your grinding problem.

[911quest]

Rebuilding a g-50 is actually a little easier then a 901 or 915 you don't have to full with shift fork adjustments, on the g-50 only shift fork to adjust is 5th. It takes alot of the guess work out of the transmission rebuild.

[irobertson]

Hi gents,

I am in the middle of doing a clutch and a general clean up and seal replacement on both my engine & trans. Part of this will be new gaskets for my G50.
The trans behaves well, so I'm not planning on a complete disassembly. I just want to remove the main case, put a new gasket on, the put it back together.
I have the rear case off and was able to remove the reverse gear and the slider, but now I'm stuck.
Looks like I need a puller to get 5th gear off the output shaft.
There doesn't look like there is much clearance to get a puller in there.
Is there a specific tool for this?
Not sure if reverse & 5th need to come off the input shaft to get the case off.
Any info would be appreciated.
Thanks

[jclporsche]

I'm not finding much help on the trans either. Have my engine out for rebuild, and just want to replace the seals on the in & out put shafts. I' thinking I can pull the input shaft seal without removing the shaft, but haven't tried yet. Anyone have any comments on that?
I'm also thinking about adding a ltd slip dif, the gear type (not clutch pack type). I don't track it, more of a daily driver. But want to eliminate the single inside wheel spin I get occasionally on power starts, especially on corners.
Thanks for any advice. You guys are always a great help.

[KTL]

Yes you can pull the input shaft seal w/out trans disassembly. But be careful when trying to extract because you can push it inside the diff housing. There is no "bottom" to the input shaft bore. It's a straight through hole without a step in it. So make sure your hook tools don't push it in too far.

But since you want to replace the diff, it actually wouldn't be a bad thing to push the seal into the diff housing. Then it would be free of the bore and you could cut it with a pair of snips. Removal of the diff is a piece of cake and since you want to replace the output shaft seals anyway, you are partly 1/2way there when you remove the output flanges.

If you change the diff, you have to reset the spacing/pre-load on the side bearings that are mounted on the diff. The preload is adjusted with varying thicknesses of spacers beneath the bearings.

[Dan J]

I agree with Tony, I think it's a very straightforward trans to repair. The factory manual is very good for these so I'd try to get it. You will need 2 specific pullers

[88911coupe]

Are the special "pullers" generally available...what's the cost or could you rent them?

[jclporsche]

@KTL: Thanks Kevin. That seems odd that it's in a straight bore. I would have thought there would be a bearing directly behind it. Must take a special tool to place the new one in square as well.
I'm still trying to decide if I can afford the new posi. The engine rebuild is taking its toll on my wallet. May end up just resealing it.
The magnetic drain plug had a lot of iron on it. But the trany was working fine for the last 6 years I've been driving it. I will probably have to back to it after I get my new power, I will probably find the weak link.

[KTL]

Buck,

One of the pullers is really long. It's probably not one that is commonly found. It has really long arms on it.

No special tool needed to seat the new input shaft seal. Just slide it over the shaft and tap it squarely into the bore. I think I used a length of PVC pipe to tap it in. Just make sure you push the inner diameter lips around the shaft so the lips sit properly against the shaft.

The material on the magnet is likely synchro material. Because if you don't have a limited slip (friction disc type) differential installed now, then that magnetic material could not be coming from the friction discs.

[Peter Zimmermann]

Originally Posted by 88911coupe

Are the special "pullers" generally available...what's the cost or could you rent them?

Contact your nearest shop and ask them when their local Snap On tool truck stops by. Check out their puller selection that starts with a "CJ" letter designation. They are usually called gear/bearing pullers, some come in sets, some can be bought individually, so measure your distances so that you'll know how long the jaw/arms need to be.

The pullers that I use for G50 work are additions to a set that my shop used for a variety of jobs. There are times, when working in tight spaces, when you must grind the puller arms to fit. Of course, any warranty is voided, but if you use proper grinding procedure you probably won't have an arm/jaw break.

[Jgordon]

I thought I read somewhere that the synchros were brass? Could be wrong.

[KTL]

Originally Posted by Jgordon

I thought I read somewhere that the synchros were brass? Could be wrong.

That's correct. Scroll down to the very bottom to see a picture and the steel type upgrade

California Motorsports Porsche G50 5 speed transmission section