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Old March 29th 2008, 14:59
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G50 Conversion project without cutting torsion tubes

Finally today I had the opportunity to put the 915 and G50 ('87-'89 model) next to each other and I thought you guys might find this interesting as well.

Axles/CV-flanges on exactly the same level:


Difference in length measured at the nose cone where it hits the torsion tube is then 3,5 cm.


Scenario when belllhousing is level, but when the G50 has had its bellhousing shortenend up to the first rib, so I have put it one rib backwards:


Difference in length is then a mere 1,5 cm:




So its still longer, but only a little, when you shorten the bellhousing (which may also implicate the need to have the input axis shortenend as well, which fyi requires complete disassembly..).

Other interesting fact was that the width from axle flange to axle flange is 25,0cm for the 915 and 24,8cm for the G50! So its virtually equally wide.
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Last edited by Wally; April 13th 2009 at 03:48.
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Old March 29th 2008, 19:10
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Hi Wally

So does this mean that your going G50? It also appears that the centre of the CV mounting flange is closer to the bellhousing once the bellhousing has been shortened on the G50.

Steve

G50 next to a Type 1 box.
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Old March 29th 2008, 23:41
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Great pics and information Wally.

Thanks

Sandeep
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Old March 30th 2008, 09:21
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Quote:
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Hi Wally

So does this mean that your going G50? It also appears that the centre of the CV mounting flange is closer to the bellhousing once the bellhousing has been shortened on the G50.

Steve
No, not going G50 just yet. The mag 915 is sooo much less weight that I would rather keep the 915. Only when it breaks (due to turbo drag starts or s/th like that), I'll probably need to switch.
Just exploring options

Yes, closer, but not in line, but that little would not be a problem at all with the CV's or axles.
Just want to show that if you would really put your mind to it, it would be possible to mount a G50 without cutting torsion tubes. Total extra length would be just under an inch compared to a stock type 1 gearbox. Most exhausts will allow for this, given you have the late model bulged rear apron.

I find it still very funny that even a high tech porsche G50 type gearbox, which was used untill about the end of the nineties, still fits directly (stud wise) onto a vw type 1 engine from the thirties :-)
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Last edited by Wally; March 30th 2008 at 09:25.
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Old March 30th 2008, 11:10
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Interesting info wally, I'm still going to have to do some serious cutting when going scooby and G50 though!
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Old March 30th 2008, 17:46
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Hi Wally

Are you able to give us weights on the 2 transmissions? What you said about VW Porsche sharing the same bellhousing bolt is very interesting, Porsche must have made compromisers with clutch size in the later years.

Steve
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Old March 31st 2008, 14:34
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Interesting info wally, I'm still going to have to do some serious cutting when going scooby and G50 though!
Well, I just pointed out the cutting is entirely due to that silly subahru engine...
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Old March 31st 2008, 14:43
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Hi Wally

Are you able to give us weights on the 2 transmissions? What you said about VW Porsche sharing the same bellhousing bolt is very interesting, Porsche must have made compromisers with clutch size in the later years.

Steve
Yeah, that is true and apperently possible as the stock G50 clutch size is 240mm and earliest clutches were 180mm IIRC. But you already knew that of course

Weight of the magnesium cased 915 was about 44kg without support beam and the G50 was about 25kg more heavy iirc.
The weight is due to the alu case and that HUGE ring and pinion of the G50. Size does matter when it comes to strenght in boxes is my understanding more and more. I think a Mendeola box for instance is about as heavy as it is strong. Bearing in mind it has only 4-speeds of course so it saves the weight of the 5th gear.
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Old March 31st 2008, 18:11
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Hi Wally

My Subaru motor came with a 240 mm clutch, I thought it might fit into the G50 bellhousing, no way.

Talking about stronger transmission, when I win the lottery I would love to fit one of these, the same people that make most of the gear sets for other manufacturers and are supposed to be stronger than Mendeolas http://www.albinsgear.com.au/pTransmissions.html

Steve
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Old October 13th 2008, 04:39
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Its been a while since I had thought about the G50 tranny, but recent developments in the engine department made me have a second look at the conversion.
The drag slicks I now use in the 1/4 mile do give extra strain on the 915. My best 0-60ft is now 1.76 with a 2200 lbs (1000kg) car with me in it and it might get even lower with less air and more heat in the tires, which I anticipate to come next year.

Strengthening the 915 can be done with a heavy duty side plate with 930 bearing from WEVO as well as a combined bearing carrier for both shafts in the tranny, also from WEVO.
Both measures cost quite some and then it would still be no guarentee that the 915 will hold for any length of time.
The G50 will give this guarentee almost certainly, although I am not sure if my old well-used G50 is any good. Synchros for these are quite expensive as well.
It may also take a lot of time to adapt the new tranny and clutch to a type 4 and its 20-25kg heavier which is a lot.
I still think its the right way eventually as that stupid stock 2 ltr engine with a turbo gave 345 Nm and 270 hp. The new 2,2 turbo with more displacement (10% more), much better flowing heads and a dedicated turbo cam (at least another 10%) might easily have 20% more torque, so about 415 Nm could be expected at 1 bar or 14.7 psi boost.
Drag race starts and over 400Nm is not something a 915 is designed to cope with. Its as simple as that imho.
So I can wait till the 915 destroys itself or I can try to save the nice rebuild 915 and use it maybe in my daily 412 in the future. Not a difficult decision anymore when you reduce it to these simple facts.

As the engine is out now and the new 2,2 ltr parts are getting slowly ready, so now is probably the best time to remove the 915 and start investigating the G50 installation.

First of all, the shortening of the bellhousing I see as mandatory for how I want the gearbox to be positioned in the car. I.e. not cutting the torsion tubes and loose structural strength, which neccesatates new pieces of even heavier iron strcutures welded in elsewhere.
A local company wants to help me machine off the first rib of the bellhousing
Also the VW Bus 228mm flywheel seems the best solution, so i will probably order the aforementioned KEP clutch. An annual throw-out bearing still seems the best solution for that. Then I don't need to order the G50 update kit for the original G50 hydraulic relase arm bearings, which still works with a pull type TO-bearing system anyways and that doesn't supports my 228 VW flywheel and pp push TO-bearing idea.
With the conventional 228mm pp I also think I retain the option to have a double clutch plate option for future power upgrades without using a super duper costly porsche aftermarket G50 solution with double plates.

Ok, so far only ideas and words but I' ll keep you posted.Any ideas/ alternative solutions are very welcomed as nothing is in stone yet..
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Old October 13th 2008, 16:42
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Found the shifter and shaft again





As you can see, its quite different from a 915 shifter and its operation.
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Old October 15th 2008, 02:02
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Wally, sorry to hijack the thread , but as a side issue I am going to change my ignition to sequential on my fi , and intend to use a dizzy with a magnetic pickup for the crank sensor ,i think you have already done this so have you any advice or suggestions on the subject
cheers jon
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Old October 15th 2008, 02:22
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Wally, sorry to hijack the thread , but as a side issue I am going to change my ignition to sequential on my fi , and intend to use a dizzy with a magnetic pickup for the crank sensor ,i think you have already done this so have you any advice or suggestions on the subject
cheers jon
Yes, that is a hi-jack indeed
I used a wbx 2,1 dizzy as a pick-up. It has a Hall-effect sensor. You can hook that up to the DTA, but be sure to use a shielded 2-core wire for this.
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Old October 21st 2008, 09:42
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Some pics when positioning the G50/01 between the forks. It seems that only some of the horizontal parts of the forks need trimming:





I decided to order an organic disk from Kennedy, G50 center, 228mm and spring centered. Flywheel will be a lightenend bus 228mm unit and for now a stock pp to do some measurements.
Plan is to mount up a dummy type 4 case to see what needs to be done to get the clutch engagement working. I hope to be able to fit an annular hydraulic throw-out bearing instead of the pull style arm that is in there now.
Anyone know what the most shallow universal hydr. annular TO bearing is on the market?
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Old October 22nd 2008, 08:46
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Hi Wally

I was going to use a Saab throughout bearing until I went full G50 clutch.

Steve



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