Porsche 915 trans installation

[Wally]

Hey guys,
Does anybody have experience with the installation of a 915 trans in a IRS pan?
I have a 915/12 transmission (4-speed) which I would like to install one day (to be followed by a 5-speed, when money allows). I've read the tech article on the 901 installation, but think that this box is 'sligthly' different.
For one, the length. I've placed the 915 next to a irs beetle trans and the length from the driving flanges to the nose cone is much, much longer. The length from the flanges towards the bell housing seems equal to the bug trans.

Since the length towards the nose cone of the trans is so much longer, it requires cutting up the torsion housing to make way for the tanny. Therefore you must use a coil-over shock towers as your rear suspension. Although a lot of (cutting and welding) work, it seems relatively straigtforward.

My big foreseen problem will probably the CV joints: Beetle is 9 cm diameter, bus (T2) has 10 cm diameter, both with VW splines to fit the beetle/bus axles, but the 915 has 11 cm driving flanges and the Porsche CV joints uses porsche (not VW) splines, at least so it was mentioned in the tech article on the 901 installation.
Has anybody tackled this already (preferably with parts that are not only available in the States...) ?

And: would I need a 911 pedal set-up assembly or can the bug pedals be modified like with the 901 set-up (tech article)?
What are the differences with the 4-speed shift/linkeage as opposed to the 5-speed shifter/linkage parts?

Hope to hear from you all with any or partly information.

Walter

(burn rubber, not oil)

[chigger]

Michel Ghia had a good article on his site. I am installing a 901/911 five speed and I believe it is just about the same as the 915. I can't say for sure as I haven't seen a 915 trans. The trans fits up tight against the torsion tube, but the rear mounts which are the important ones are in the right place. The front mount had to be make up. The trans shift from the bottom instead of the top like the bug so a hole has to be made in the bottom of the pan. A thing Model 181 shift rod was bent with the S at the very end to clear everything. A Scat dragfast shifter with modified gates, shifts all the gears so I think it will work OK as the car hasn't been driven yet. I drilled and tapped the bus CV pattern on the big Porsche CV drive flange. The result is quite satisfactory. The Bug CVs are too small. The clutch linkage wasn't too bad either. I just redirected the bowen tube from the top of the trans to the bottom with a custom tube mount kinda looks like a mirrow image of the bugs. And now for the bad news. The clutch arm you use depends on the engine and trans you use. I am not happy with that part of the modification. I may just go with a slave cylinder. Over all I didn't think it was all that hard to do. Expensive!!!! Hope this helps.

[kiwivw]

Hi Guys,

I'm currently in the middle of my 915 installation. I decided to chop the torsion center out and will be bracing the top with box steel (probably 1.5"). I will of course now be running a coil-over setup (thinking of SPAX from the UK at present with helper springs to soften the daily drive). I'm also installing 944T trailing arms (i'm still researching the CV issue :( ).
With the center torsion housing removed the CV joints on the trans seem to line up with the the trailing arms.
I also made mounts that i welded to the trailing arm housing underneath, these will then use universal bushing to mount a front transmission mount.
I ended up purchasing a 911 shifter and shaft (with i wil lengthen to suit). As far as clutch pedal, i will be modifying the existing VW one.
For a lot of this information and design considerations i used the articles you have mentioned plus Rich's site http://www.ricola.co.uk/

[Wally]

Thanks guys for the helpfull info and comforting remarks about the installation. I will try the measurements once more, before hacking up the torsion housing.

Could you forward me the site of Michel Ghia ?

Walter

[Alex]

You will find it in the links section of the main site.

Alex

[typ4boy]

ahhh the good old 915 box in irs bug pan, allmost like 901 till it comes to cv joints. well this is what i did, bearing in mind i use 944 trailing arms.g box end remove the cv drive flange (if its an early type with 930 size cv,s) and replace it with one from a 914 box, goes straight in then you can use 914 cv because this has the same inner size fitting as bug driveshafts(which i use) then brake end use the 944or type2 size cv because this all so has the same inner size as bug drive shafts. regards Lee www.laperformance.co.uk

[Wally]

Type4boy,
This is brilliant info !!!! I think a lot of us will be very happy with your solution of using the 914 flanges and sharing this info with us.
I also use teh Alu 944 (turbo cup) trailing arms which indeed have bus CV's size flanges. I also had to use the bus axles, since my arms are about 10 cm each wider in track...They fitted!

Do you by any change have -1,00 mm (at the crank) connecting rod bearings for a 50 mm standard 2 litre type 4 application?? (one of my other 'little' problem)

Many thanks again,
Walter

[chigger]

I knew that the 914 CV drive flanges would fit the 915 trans, but after a year of looking, mostly Ebay, I gave up and went a different route. I am using a 901 clutch arm with a 914 flywheel for a T4 engine. How have the rest of you adapted the clutch arm? Mine drags a little. It may require the install of the engine to fine tune.

[typ4boy]

chigger what box have you got if it is early type its apush to release, as opposed to vw pull to release. simple either way junk the hole cable assy and convert to hydro i used every thing off a type 25, wedgy, vanogon what ever we call them. rergards Lee.

[ricola]

Hi Lee,
I want to convert my 915 to hydraulic operation but being a rhd chesil there is very little room for an extra m/c.
Any ideas? Do you have any pics of your trans install? I've seen your site and the Volksworld article but not much trans detail in there...

Rich

[chigger]

Mine is a pull box just like the bug. The clutch arms comes out of the bottom of the trans instead of the top. I can't sell it as it has been modified and won't fit a Porsche any more and the pan won't fit a bug trans any more. And there is too much money tied up in it to quit now. Anyway it keeps me from going crazy at my dead end job. One of these days I will get a digital camera which takes pictures big enough to tell what you are looking at and post some pictures.

[typ4boy]

hi rich,i used a type 25 clutch master cylinder, placed it next to the brake one and used a bug brake rod and welded this to the clutch pedal then routed a copper pipe to the type 25 slave cylinder. we welded a bracket to the frame horns for this then . the t25 master cylinder is quite small and fits next to the 944 master cylinder ive used but mine is an 03, maybe more room than torsion pan?. currently building another GL car based on 79 torsion pan bug with late 915 box with its own oil cooler which is taxing as the oil cooler is right where the frame horns are, but doing a photo rebuild for the web site, installation will be as 03 if you require more info rich give us a call ,regards Lee.

[ricola]

Cheers for the reply Lee,
I'm sure an '03 has more room up there, but even more room is freed up as your car is LHD. My problem is that there is a chunky Chesil box section where I would have to cut through and also the extra m/c would be stuck between the brake one and the centre tunnel and I'm not even sure there is physically enough space!
I saw some pics on One on One's site of a cab with a new box welded in and the brake m/c was moved over but doing that much work with the body on the pan is too much work with no acccess to plasma cutters etc etc.

Rich
PS Look forward to seeing your new build up!

[Wally]

Hi guys,
Since then, I've changed the 4-speed for a 5-speed with type number 915/40.
I sorta assumed that it also had the (too) big 110 mm driving flanges. NOT !! This one has 100 mm drive flanges with 8 mm bolt holes, so the type 2 CV's can be easily used!
I was much surprised, to say the least, but very happy. We are one step further down the road...
Thought I joint the info with you.
All the best,
Walter

[chigger]

Could you post the type make and model of Porsche trans with the T2 cvs. It would make things a whole lot easier. Thanks.
From the posts on this and other forums I think there are alot more Porsches in europe and probably a few models we don't have here in the US.

[Richie]

Hi Walter,

So you found youre flanges, and complete with a gearbox! Congrats!

Cheers,

Richard

[Wally]

Thanks Richard,
Chigger, all I know is that this is a type 915/40 trans and that is is used on 2,7 ltr models, from 165, 175 to 210 hp, model year around 1976. I'am almost certain that there will also be boxes with the same type and from the same year that will have the 'wrong' flanges.
I haven't been able to identify the years that have the 100 mm flanges or the 110 mm flanges. Just keep your eyes open I guess.
Good luck,
Walter

[kdanie]

There doesn't seem to be much consistancy when it comes to drive flanges on Porsche trans'.

I have a 902 5 speed from a '69 912 (not a high HP car) that has the large (110mm?) 930 size flanges, I have a 914 5 speed with the small type 1 size flanges (as expected), I have a set of what I think are mid-late 70s 911 flanges that are 930 size but are NOT the same as my 912 flanges!

The 914 and 911 flanges on my bench are shorter by about 1/4" than my 912 flanges, the seal area on the 911 and 914 flanges are different lengths but the seal rides in the same place. If I were to install the 911 or 914 flanges in my 912 trans, the drive splines would not be fully engaged and may strip when I dumped the clutch.

I keep hoping to find some 100mm (944/type 2 size) flanges, I guess I'll keep looking. Who knows how many sets I may end up with!!

ken

[ricola]

I have a 915 froma 911SC, the mid year version with electronic speedo but not the external oil cooler. It came with type 2 sized CVs...
Makes the whoel Porsche rear end conversion much easier!
Rich

[typ4boy]

hey rich, while KIT was @ my shop the other day checking out my new 915 install we had a long disscusion about hydro clutch in rhd we came up with a possible solution. where the cable conects to in the tunnel why not make some sort of arm and rod attachment that would take it out into the frame head where you could mount a cylinder we think this would work and sorts out the rhd problem with hydro clutch, hope this helps regards Lee L.A.P

[ricola]

Cheers for the suggestion Lee, but I have my radiator up front so no room. Somebody mentioned that they had seen a car in Ireland that has this solution so it can be done...

I'm trying to find out how Russ Fellows has his done as looking at a pic on Paul Cooper's site he now runs a hydraulic set-up.

Rich

[hot66]

Originally posted by ricola
I saw some pics on One on One's site of a cab with a new box welded in and the brake m/c was moved over but doing that much work with the body on the pan is too much work with no acccess to plasma cutters etc etc.

Rich
PS Look forward to seeing your new build up!


Hey, thats my cab :D :D

Hydraulic clutch & 944 m/c & servo :D

[typ4boy]

rich i understand but your rad is not that close to the bulk head is it ? think you might have got the wrong end of the stick. the clutch cylinder is very small it would be in the same position but on the left hand side as you brake master cylinder hope this helps regards Lee L.A.P

[ricola]

Thinking about it I may be able to squeeze an m/c onto the front of the framehead, clearance would be very tight with the radiator though, there really is very little space with the fans etc etc. Would be a nightmare tuning the pushrod length!

Lee, did you mean having the clutch master in the position of a LHD brake master? Not sure how you would get a rod from the clutch pedal across like that without having a bent rod. I will be very tight for room everywhere soon once my wishbone suspension/steering rack and cooling pipes are all mounted...

Rich

[1956oval]

I don't know which side of the pond your on but over here lotsa my customers are coming in with hydraulic throw out bearings that expand to disengage the clutch. I haven't looked for them so I really don't know where to buy them yet. Most of these customers are racing sprint cars with american V6s and V8s but I see no reason one couldn't be adapted. They require drilling a hole in the bellhousing for the line that feeds it. Its a slave cylinder and throw out bearing all in one. They are being used by ford and chevy in P/Us and passenger cars. I know the Cavilier we had used one. just install it and don't pull the plastic clips as they are made to break apart after the system is bled and used.

[ricola]

The 915 is a pull type clutch, as far as I am aware there isn't a variant of this type of bearing that would work. Besides, ti si easy to fabricate a linkage below the trans with a regular slave cylinder...

Rich

[Wally]

In order to make room at the nose cone side of the trans, I probably have to cut out some piece of the central torsion housing where the torsion bars are fitted in their splines...
Would it be possible to use the shorter torsion bars of the swing axle models and relocate both the pick-up points outward, thus creating room for the 915 nose cone and retaining the torsion bar set-up?
Anybody thought of this before? or done this?
Thanks,
Walter

[ricola]

You are right, I have heard of this being successfully done before, but never seen it...

Rich