Boxster transmission on 914 anyone?

[junjun11]

Hello pelicanites. I am in the very early stages of experimenting with an adapter kit that will mate a boxster 5-speed transmission to a type 4 (914) engine. I started this project because I am very unhappy with the original tail shift tranny on my '72 914. I upgraded to a side shift transaxle but still i am not satisfied with the "feel" of the gears engaging.

Photos show the mock-up of this setup and hope to advance this project, if time permits, in a month's time. I already have the correct pressure plate & clutch disc and the next thing to do is to fabricate the customized flywheel.

The purpose of this project is to eventually come up with a working "adapter kit" which I can sell since boxter 5-speed trannies are becoming quite abundant & affordable. I also plan on fabricating a flywheel that can be mated to a non-EFI porsche 6 engines since they the same mounting holes/pattern on the type 4 engines... Comments, suggestions are highly welcome...

[Dave at Pelican Parts]

Where is the starter? I believe that on the Box, it goes on the engine side. On the 914, it goes on the transmission side.

--DD

[junjun11]

Hi dave, it will be located on the tranny side. A portion of the tranny will have to be cut out to accommodate the starter. A spacer-bracket will have to be fabricated also so that the type4/flat 6 starter sits as far out from the tranny as possible so as to minimize its intrusion into the tranny.

Right now, the most feasible location I see is on the 12 o'clock position. As mentioned prior, this is on it's very early stages of the project and a lot of "experimentation" has to be done. So i have prepared two 5-speed trannies as candidates for this project..

The boxster S transmission seems like an easier tranny to work with because a lot of the parts from existing 911 models can be utilized. But unfortunately, only the 5-speeds are very accessible for me.

I am taking the measurements of the flywheel this weekend and take it to the machine shop after.

[infraredcalvin]

Looks like you'll have to cut out the trunk to fit that in. A bit of an overkill for a type IV, but if you can make work with a high hp 911 engine, that might be a good alternative to a 915 or 930 box.

[infraredcalvin]

Slow internet/double post, sorry...

[Nostril Cheese]

Its a lot easier to just re-work the stock transmission to have a cable shifter.

[lorenzoscribe]

Nostril Cheese,
Some time ago, I found a cable shift do it yourself website for the tail shift 914 using a shifter head from a Mitsubishi Eclipse, a couple of push pull cables and some fabbed brackets. The citation is Porsche 914 cableshifter DIY.

Is that the cable shifter you are referring to, or have you seen something else. I would be very interested in alternative ideas on cable shifters.

Larry Steckel
1971 Porsche 914.

[Dave at Pelican Parts]

In more recent decades, people have used a Boxster cable shift setup. I think the cables are even pretty close to the right lengths. Might be an easier alternative in some cases.

--DD

[Nostril Cheese]

Originally Posted by lorenzoscribe

Nostril Cheese,
Some time ago, I found a cable shift do it yourself website for the tail shift 914 using a shifter head from a Mitsubishi Eclipse, a couple of push pull cables and some fabbed brackets. The citation is Porsche 914 cableshifter DIY.

Is that the cable shifter you are referring to, or have you seen something else. I would be very interested in alternative ideas on cable shifters.

Larry Steckel
1971 Porsche 914.

It's just geometry and a lot of measuring. I've seen a variety of different approaches.

Use the cable ends off the stock Boxster cables and have some cables made up to the length you want.

[Mike Bellis]

Boxster cables are the perfect length. I use them on my 5 & 6 speeds in the 914. Boxster shifters are cheap.

[db9146]

Originally Posted by Mike Bellis

Boxster cables are the perfect length. I use them on my 5 & 6 speeds in the 914. Boxster shifters are cheap.

Mike, what 5-speed or more interestingly, what 6-speed are you using in a 914? And behind what engine?

Please elaborate.

[Mike Bellis]

Originally Posted by db9146

Mike, what 5-speed or more interestingly, what 6-speed are you using in a 914? And behind what engine?

Please elaborate.

I have an Audi 1.8T with a 012, 5 speed or a 466 Getrag 6 speed. The 012 is the same as a Boxster 5 speed from most years. The 466 is a 2005-2008 Cayman S /Boxster S 6 speed. They have the same bolt patterns which work on Porsche or Audi engines.

I run a Boxster 5 speed shifter for both transmissions. I did clearance it and add a short **** kit. I use Boxster cables for the 5 speed and Cayman S cables for the 6 speed.

They both use the same slave cylinder with a WIlwood master cylinder up front.

The 012 has 100mm flanges and the 466 has 108mm flanges.

Read my build thread for more info.

http://www.914world.com/bbs2/index.php?act=ST&f=2&t=187914

[lrodri64]

Junjun
Have you thought on a Subaru gearbox?

[junjun11]

Hi everyone. Well, i did eventually get it to work here is what i did: (also note that this was for a 904 replica)

1.) Fabricated and adapter plate

2.) Fabricated a flywheel to work with a Mazda/ford starter because the boxster bellhousing wasnt deep enough to take a regular starter. The mazda/ford starter had it's gear offset to the edge of the starter body, hence clearing the shallow boxster tranny profile.

3.) Used a clutch disc and pressure plate from a 92-98 Audi A4. The boxster setup is a DMF and the Audi's was an SMF so it worked well with the custom flywheel.

4.) Had to cut out a notch on the tranny because as mentioned by Dave, the starter on the TYPE IV is on the tranny side.

5.) Utilized boxster axles (shortened). Aparently, the boxter stub axles have a 40mm OD. Both cars actually used same rear wheel bearings!! So it just slipped right through.

6.) Utilized boxster shifter and cable along with the tranny.

Pros:
-Boxster-like precise shifting. Hard to miss a gear.

Cons:
-Gearing not compatible with the TYPE IV. Had to reduce tire size significantly.
-Boxster tranny was much larger than the 914 tranny. So it had clearance issues on the frame.
-Starter orientation is on the wrong side.
-Lots of custom fabrication

Was it all worth it for the purpose of better shifting: Driving experience, YES! Car shifts like a dream. Cost? NO! but then again, that is always the case with R&D. As mentioned, it would be best to pair it with the 6-cyl, up to the 2.7 engine. If it's for the 3.0 and 3.2, better to go with the Boxter S tranny.

I will end up using a custom cable shifter on a tail shift tranny since the Boxster tranny was too big for the 904 frame.

[totle]

Very nice project.
Please update with more pictures.
I have been looking at this myself. My plan was to take off the bellhousing on a 911 transmission and cut part out from the boxster transmission. But this has just been in my mind.

Will be nice to see how you solved the starter.
If you placed the starter on top, will it then fit under the 914 ?

Looking for updates. Very interresting. The boxster transmission can take more power than the 901, and they are very cheap (same as audi/vw)

[larrym]

what's the likely actual cost for the entire conversion ??

your kit delivered USA, trans ($400+ on ebay), misc parts, plus labor?

i'm hard pressed to understand there is a profitable market for this (not unlike Bott's 916 kit)

[junjun11]

Originally Posted by totle

Very nice project.
Please update with more pictures.
I have been looking at this myself. My plan was to take off the bellhousing on a 911 transmission and cut part out from the boxster transmission. But this has just been in my mind.

Will be nice to see how you solved the starter.
If you placed the starter on top, will it then fit under the 914 ?

Looking for updates. Very interresting. The boxster transmission can take more power than the 901, and they are very cheap (same as audi/vw)

Totle,

I cut a notch on the boxster tranny. At first, i cut a really large chunk because i wanted to use 911 starter. But the boxster's transmission body is much larger than the 915/901 which didn't allow the use of the also large 911 starter. As the saying goes, i should've measured 10 times and cut once. Hence i resolved to a "top-mount" starter from ford/mazda..

As for the 914 application, i honestly think that it will hit a portion of the trunk floor panel. My application was for a 904 replica. But it looks like it will also clear it if i positioned the starter at a different angle as shown in this 914 conversion, although it uses an S tranny, which is very different from the stock boxster's:

https://grassrootsmotorsports.com/reader-rides/503/

So sorry i haven't posted photos yet because the ones I took are crap. I will try to post good photos.

Originally Posted by larrym

what's the likely actual cost for the entire conversion ??

your kit delivered USA, trans ($400+ on ebay), misc parts, plus labor?

i'm hard pressed to understand there is a profitable market for this (not unlike Bott's 916 kit)

Larry, I haven't actually looked into selling a kit because my purpose was to fit it in my project. But just to give an idea, here is what i spent: (just from rough memory as this was a project that took almost a year to work on).. keep in mind also that much of the cost was on trial and error so i had to factor that in:

Adapter plate = $300
1992 to 1998 Audi A6 Clutch disc and pressure plate (valeo) = $250 +/-
Boxster tranny = $200
Machining (shortening) of boxster axles = $80 to $100
Custom flywheel = $80 to cast the rough profile, $100 to have it machined.
Used ford/mazda starter = $100.

The one and only reason that I ended up shelving the project is because the top-mount starter hit the frame of my chassis. But if this was for a 914, i surely will go for it because as you know, the 914's shift is like shifting with spaghetti noodles, even the side-shifter ones are not much better..

As mentioned i did get everything to run on the stationary chasssis on jack stands(engine running, shift, clutch, starter) but i didn't have the chance to get the car on the road. I also feel that the type 4 and the boxster tranny are mismatched because the TYPE 4, 2.0 engine has a much shorter stroke than the boxster's.. but i think that could've been compensated with smaller tires, i guess.

by the way, I might still have the flywheel dimensions if anyone wants that. and i will also try to get the adapter plate dimensions on paper so i can post it here.

I will definitely put photos up.

[totle]

Any updates?

[Miguel K.R.]

Originally Posted by junjun11

Totle,

I resolved to a "top-mount" starter from ford/mazda..

https://grassrootsmotorsports.com/reader-rides/503/

I haven't actually looked into selling a kit because my purpose was to fit it in my project. But just to give an idea, here is what i spent: (just from rough memory as this was a project that took almost a year to work on).. keep in mind also that much of the cost was on trial and error so i had to factor that in:

Adapter plate = $300
1992 to 1998 Audi A6 Clutch disc and pressure plate (valeo) = $250 +/-
Boxster tranny = $200
Machining (shortening) of boxster axles = $80 to $100
Custom flywheel = $80 to cast the rough profile, $100 to have it machined.
Used ford/mazda starter = $100.

By the way, I might still have the flywheel dimensions if anyone wants that. and i will also try to get the adapter plate dimensions on paper so i can post it here.

I will definitely put photos up.

--------
Hello, can you please send me the flywheel dimensions. And do you have drawings with dimensions for the adapter plate ? (I have seen them in the internet but with low quality and it is almost impossible to read the dimensions).

As I am in Europe I am going for a Jaguar X-type starter, which is similar to the Mazda/Ford 6 cylinder starter, which I guess is not easy to buy here. The Jaguar starter for the Diesel engines works counter clockwise ( I guess that is what I need for the Porsche 993 engine) and is stronger with 2.1kW than the petrol/gasoline models which have 1.7kW.

I was considering to make new gears for the starter, to match the gear of the flywheel of the 993 engine (actually instead of the dual mass flywheel I am planning to use a Kennedy Engineering Products flywheel).
Is there a reason why you made a flywheel instead of making the gears for the starter ?

Thanks in advance for your help

Miguel