GT40's with Porsche G50 Trans - Pics needed

[Big-Foot]

Hi,

I'm in the process of having a G50/03 built for my upcoming GT40 build.
This is a 1991 with the longer tail-cone - single donut mount.

I've been told that all I need to do is mill off the donut mount and it will work in the chassis. As it turns out, the donut mount is also the support for the shifter shaft so it can't be cut off entirely.

Does anyone have any pictures that they can share of the rear sections of their cars with G50 (both early 87-90 and late - like mine) that they could post?? I would really like to see what I'm getting myself into here.

Also if anyone has an earlier cover they would like to sell - that would cure the problem as well..

Thanks for your help!
(edit) - I attached a couple of pics.. There is a bearing and a seal that are to be pressed into the end of this housing where the shifter shaft sticks out. There is also a pair of balls (detent balls?) that are installed inside this housing that the shaft rides on..

[Fran Hall RCR]

The short tailhousings are sometimes hard to come by...lots of Porsche guys use them when retrofitting the g50 variants into earlier 911's .

Machining off the extra mount is totally acceptable..

[Dean Lampe]

Does the trans just hang off the back of the engine? Are the engine mounts strong enough for that?

[Big-Foot]

Hi Guys,

Okay - In the interest of helping other saps such as myself figure out how to do this properly, I have spent the time to create an illustration of the problem and I hope that we can do the GT40 community a service by weighing in on this thread with pictures of how others have mounted their G50's as well as how this can be accomplished without the purchase of a different end cover or transmission.

Please take a look at the following images.
The first is of a staged operation on a 91 and later G50 end cover
The second is a drawing of the earlier G50 end cover.

Note that the shifter shaft in the later one will stick out a good deal further than the earlier one. Just "whacking off" the excess shaft is not as easy as it would appear. Cutting off the additional housing material removes the bearing and seal mounting surface and I believe it may also encroach on the area that would have the detent / alignment balls.

[Fran Hall RCR]

Dean,
the trans is hung from the engine adapter plate which itself is attached to the chassis with two 5/8 Grade eight bolts,the adapter plate takes the trans load not the engine mounts..
There is also an extra provision for the high power track guys to attach two extra supports should they feel so inclined.

[jmracecar]

Randy, great drawing sequence, perfect. That is exactly what I was trying to communicate to you with all the separate images, but not this clearly.

If we cut the shift rod opening short, we would also want to cut the rod short, or use the earlier style. It is cheap enough from Porsche, unlike the cover. The shorter rod 950.303.109.05 lists for $122.14, however Porsche dealers have no clue when a given part will come in from Germany. It could be next week, or next year, for any given part ordered any given day. You can order the same thing once a week and see different delivery results.

The earlier cover is around $1000 new, as we discussed, so this is why used ones are so darn scarce.

staged operation on a 91 and later G50 end cover

Where you say 91, we should say 1990 & later.

Now, for future use & other cars, if we do in fact have room to run the 1990-1994 end cover as is, then we have room for a 993 6-speed trans instead of the 5-speed. They have the same overall length, the key packaging difference being a bulge of the sixth gear into this mount area. The net length is the same, and the round mount for a Porsche ends up in the same location.

Also note the 2 bulges in the early style cover, which are still present in the later style cover, will still be there after machining. If that makes any sense. The machined cover would look more like the earlier one than first appears in your sequence drawing #3.

[Lynn]

Here are some pics for you:

1) G50/52 that has been modified............These 3
2) G50/50 nose side view.......................are shown in
3) G50/50 nose straight on.....................Porsche position
4) G50 mounted in my Sabre (highlighted for clarity)

Lynn

[Big-Foot]

Great info!! Please keep it coming!
In the top image that Lynn posted that shows the modified cover, it appears that it may have the earlier model shifter-shaft seal installed.
Lynn - do you have any other pics of this?

Also - From another post I found this;
Porsche Transmission Questions

Originally Posted by Kalun_D

"On the nose cone, it looked like a guy had just cut off part of the triangular extension for the doughnut mount, and simply shortened the gear shift selector. ""

There's a seal in the very end of the case and behind that there's a roller slide bearing. So when you hack the back off the case you have to machine the shift shaft bore to two different sizes, for the bearing and the seal. Luckily it's made to do this , whether intentional or not, the bore is smaller behind the oringinal location of the bearing/seal, so all you do is open it up to the bearing/seal size further back. The unmachined bore about 14mm dia ID, the bearing is about 16mm OD and the seal is about 20mm OD. I don't see any real reason to go to side shift unless you have some different clearance issue. Lots of the G50's have been run with rear shift, unless the 50- 50 or the 50 -52 is longer even with the nose hacked off.

Joel - I'll be calling you soon.. I have another bus. call to make first.

[Lynn]

Randy,

I don't have more pics of a modified nose. I only had the one for reference, but managed to get all '87-'89 units.

If you go to Road & Race: Parts Charts > Grp III-Transaxle, they have a pretty good set of break down parts charts for Porsche transaxles.

I think you'll find that the ball & spring for the shift detents is up in the transaxle and not out on the housing for the external rod. I haven't double checked it, but that is what I recall. I also think you are spot on concerning the seal for the modified nose (that must have been floating around in my noggin somewhere because that is exactly what I was thinking the solution could be; then I noticed your comment and the picture that shows just that, I believe.)

Lynn

[Big-Foot]

Great info Lynn - The Group-III link is a good one with a lot of schematics of these Porsche gearboxes.

I just spoke with Joel. He checked the part numbers for the seals on both the early and late covers and found them to be the same.

Fran - If you're still reading this thread;
Can you tell us how much clearance is needed in your RCR40 chassis for the shift-rod and housing?

This will give us some idea as to how much will need to be removed from the 1990+ housing and shifter shaft.

Posting the same question in another way to be more clear;
I guess what I'm looking for is how much clearance there would be between the body/chassis of the RCR40 and the end-cover and shift shaft of a standard 87-89 G50 transmission.
If there's only 1/4" clearance between the early cover and shifter shaft to the chassis/body - we would need to cut more off of the later assembly to function properly.

If any other manufacturers want to chime in here with information, please do so...

[Big-Foot]

Lynn - Understanding that there is some sort of knuckle clamped onto the end of the shifter-shaft which will add to the total length of the transmission as a unit, can you tell me how much room there is on your Sabre to the body-work / frame? This will help me guage how much I need to remove from the end of the shifter-shaft on my transmission.

Thank you..

[Lynn]

Randy,

First to answer your question directly, there is 4" between the end of the adapter on the shift shaft to the plane of rear body work. That said, if the shift shaft were extended, it would come out of the middle open section in a MK I tail and just clear my license plate frame (I think.) Now that that is said, the realy limiting factor is the down tubes of the exhaust, for me. As it is, in 1st gear, the head of the ball connector on the end of the in-out cable just contacts the driver's side down pipe.

Unfortunately the picture below (blown up from over all tail shot) is the best depiction of this that I have. And while I am a little embarassed to show the shift shaft setup (early) it will show the "knuckle."

[Big-Foot]

Lynn - Absolutely FABULOUS!!!!
Thank you Very much!!!

[Lynn]

Randy, you are quite welcome.

FYI for those wondering what the electrical device on top of the shifter is:

This was my first attempt at a neutral sensing switch for the EFI computer; there is also a brake type switch just before the clutch slave cylinder. (These two signals are "OR" ed together in the computer to tell it that there is no load on the engine and to provide just enough fuel for proper idle. This way the EMS can differentiate between idling along- say in traffic - vs just sitting with engine idling.) The micro switch arm with roller was supposed to ride on the bolt head that holds the adapter onto the shift shaft. Unfortunately, it kept hanging up and rolling the switch arm into a circle.

I have since relocated it to the right (pass. side) of the transaxle, on the same plane as the bell crank/linkage and enclosed it in a box. This lower position moved it from the heat of the exhaust and the box protects it from rain, etc. I fabricated a plunger arm that has a right angle with a nylon roller that rides between the twin lever arms seen descending from the adapter. This configuration has proved to be much more robust.

Lynn

PS: I have this same picture with the bell crank/linkage angles and dimensions if anyone is interested. PM or email me and I'll be glad to send it; I have a zip file with a bunch of pics and info on this setup that I have sent to others.

[JulianBW]

Here is a photo of a G50 fitted to a Chevy 350 in my GTD.

This G50 has Quafe internals so I am told?

Julian

[Pete T]

I have a copy of the Porsche PET6 in .ZIP format if anyone is interested. I would have posted it here but the file is too big. It's 126Mb. With all the questions about transaxle parts etc. this could help many. This is the Porsche parts catalog that covers all models from 356 to current, except race cars, up to almost present. I'm not sure what year it goes to because I haven't installed it yet. I have PET5 installed now and it goes to 2001. If there's a place here where I can put it let me know.

Pete