I am seeking information on converting my 914/6 901 transmission to a 915 transmission. The reason I am considering this is I have replaced the 2.0 motor with a performance 3.5 911 motor.

Any direction and advice would be greatly appreciated. [b][/b]

You most likely need a shop
The ring and pinion have to be flipped and about 5k worth of parts plus the trans rebuild and purchase

AND it makes the car feel heavier. DON"T DO IT!!!!!! (we have two here with the 915 gearbox installed and hate driving them ! Just making a linkage for that gearbox is a chore

The only game in town left for the conversion is Martin Bott / https://www.bugat5speed.de/en/

Quite a few people have done his conversion and reported good success. Rory might be able to chime in with a more professional option than me. @rgalla9146

I have a 915 Carrera with the old (NLA) Wevo kit set up by Peter Dawe. It felt like a good 915 should. It does have a heavier feel than a 914 trans but that’s to be expected. It was behind a Dawe built 3.6 in a 914 racecar. Now it’s going in my 3.4 flared car.

I have a flipped 915 just under 10k miles on it rebuilt through Renegade Hybrids. PM me. Brett

I have a Martin Bott kit that Eric and PMB put together.
The car felt more solid and heavier than a 914/4 prior to the 916 trans. Afterwards, minimal perceivable difference.

After the 916 trans it just shifts right. The 914 trans was good but I went through a couple of rebuilds of that before the swap.

I used an electronic speedo and late SC actuation for the clutch.

Definitely worth it , in my opinion, but not cheap

Sounds fun!

I am running a performance 3.2 on a 901 trans for the last 10 years and it is doing fine (~280hp). I do have a 915 swap ready to go just incase, but have been waiting to see if I really need it. I have tracked it a few times (just HDPE) too with no issues. I think if its a street car your probably OK with a 901 (just don't abuse 1st gear) if a doing heavy track then alternatively you can do a 915 or 901 upgrades. We have a thread in the paddock in regards to 901 upgrades.

Hi Brett,
Is the trans for sale? If so is it an aluminum or magnesium case? What do you mean it is flipped?

Peter also built my motor and has done extensive upgrades on this street 914/6. Unfortunately he and Keith of Powertech are too busy to tackle this project right now.

Hi George
I need to replace the clutch at this time. I have never been happy with the performance of this clutch. It tends to slip under hard acceleration. Not sure I can find a clutch that will work with the 901 trans that would be acceptable. I have somewhat babied this transmission because of the HP and Torq of the motor

The transmission is for sale but not formally posted as of yet. It is flipped, meaning ring and pinion, and was used with a 914 application. In other words the expensive part was done already and Renegade used people who know how to do it properly. Magnesium and believe it is a 1972. Gearing seemed really good and would work well will 911/6.

I’ve been running the Martin Bott kitt for several years now. Bought the kit from Martin, but all the other conversion parts were purchased and installed by Patrick Motorsports. PMS also sells the Martin Bott kit. Worth every penny.

Oh. I also have the tranny Mount, clutch and pressure plate and cable shift shifter that would go with it .

Be sure to check out the members vendors section for more info on Martins 916 kit. http://www.914world.com/bbs2/index.php?showtopic=102988

Trans and engine are in a different orientation from a 911 to a 914. Parts need to be flipped or moved to work between the two.

My 3.4 l twin plug (290 RWHP with open exhaust) has a 901 trans. It survived 23 years of club racing and now is a street hotrod. As my indy shop once told me - you can rebuild a 901 box many times for the cost of a 915 conversion. My gearbox has the billet intermediate plate and I think this isa good idea for high hp engines. As said by others, Don't abuse 1st gear and you should be fine. Another plus for the 901 is the racing shift pattern. With some good aftermarket linkage bits from Tangerine Racing it shifts very well.

If your pushing close to 300 or more HP, you can use a 901/914 gearbox and start out in second and use O for third and X for 4th and flipped H for 5th for less than half the price of a 915, but you only have a four speed trans. I’m using this combination with HD axles from renegade with my 914 v8 conversion. Works great!!

The original poster is sort of locked into building a good 915/916 box for his car. You don’t have Peter build you an engine and then “baby” it.

I’m upgrading my 3.2 to a 3.6 with my 916 trans. Love this trans!! The pull clutch with the omega spring is also much nicer than the KEP setup for a 914 trans.
Like I mentioned worth every penny and I have 5 useful gears. The above info about my v8 setup, was just to mention there are other options.

If you PM me I might have the solution you are looking for??? If
You want to pay for a core 915, then pay for the flipped ring and pinion, tranny Mount, shifter, clutch and pressure plate, yes it will be much more than a rebuilt 901. If you reach out, and we talk, you might find I might make a deal for you..

This is a rear view of the real deal 916 transaxle, which is what the Martin Bott kit = 99% identical in form and function. They also use aluminum instead of magnesium. I prefer aluminum for the stop and go of street driving, and a bit of club racing...but probably save about 8 to 10 lbs using mag.
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Thanks for the tip. I checked out the site and this is starting to look more involved than I expected. The information provided by Martin Bott is very very good and appears he has all the necessary parts for the conversion. However, these posts are from 2010. If I decide to move forward I will need to find out if they are all still available.

@Justinp71 I did a quick look and search for the paddock thread you mentioned, no luck. Do you have a link to it? 901 upgrades...

300 hp might work for a street car that is taken “easy”
The race box cut off happens at 200hp
That’s when multiple rebuilds of a 901 become cost effective with the 915
200 at the wheels when driven in wheel to wheel racing, red line 20x/lap

Is this using a cableshift on the tail end of the trans? If so, won’t fit a normal muffler.

The Martin Bott kit is a close copy of an original 916.
Converting a 915 to a 916 using these parts is best left up to an experienced
Porsche transmission specialist.
A quick list of necessities.
'Flip' the differential. Entails moving the ring gear to the other side of the pinion
shaft and adjusting differential carrier bearing drag and backlash. Special tools
and experience required.
A gearshift support bracket (supplied) has to be installed inside the trans.
This requires locating, drilling and tapping three 8 x 1.25 holes to attach
bracket. Later aluminum 915s might require welding to provide bosses to mount
the bracket.
You have to choose how you want your speedo to operate. Early
915s drove the speedo through a flexible cable just as 914s do.
Later 915s had electronic speedo drive.
You may have to choose an alternate muffler to clear the back cover of the
trans. Or space the original banana muffler back ~1/2"
You'll have to fabricate clutch linkage. Many ways to skin that cat.
You'll have to find a 1972 911 shifter to keep your 914 tunnel carpet stock
or go with a '73> 911 alloy shift tower.
You'll have to fabricate at least one shift rod depending what shifter/trans/joints
you choose.
And much more I'm certain.
I have driven mine (behind a 3.2 SS) but teething problems with the engine
and the trans and time constraints prevent me from offering
a valid impression.
I've wanted it for a long time and will have it this spring.

Patrick Motorsports sells everything you need to install a 916 trans in a 914. Shift rod, clutch cable adapter, etc. They also sell the Martin Bott 916 kit. This kit has issues out of the box. The Parts have to be clearanced and machined to work properly. I’m running an 86 trans with 108mm flanges, electronic speedo, LSD, etc. As mentioned I had to space the headers back a 1/2” to clear the backup light switch for my M&K muffler. I’m also using a 911 Jwest Rennshift. JWest was kind enough to sell me the parts to convert the 914 rennshift to a 911/915 rennshift. I personally tried Wevo, stock 915 shifter and special one year only 72 915 shifter and IMHO none shift better than the JWest 915 shifter with the 916 trans. I’m also using the later 911 pedals with clutch return spring. This works great with the 915 omega spring.

@NARP74 This is the one I was thinking of-

http://www.914world.com/bbs2/index.php?showtopic=354969

I think for the OP if you have the means then a 915 is a safer bet, if you will be mostly driving on street can probably get by with a 901.

@Sirandy are you still running a 901 on your 3.6?

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Great advice Marty! Love that "real deal 916"
I have the Martin Bott 915 built and basically ready to go, just can't bring myself to take the car off the road. I know it will end up taking more time than expected in the end and I just like driving it. One day.
Cheers!

Maybe some day....

18 years and counting ...

Martin has an online store. https://www.bott-parts.de/getriebe/umbauteile/?p=1
But I would email him direct. Sometimes he offers discounts.
In his kit, he does require a piece of your 915 trans to modify. I had to work with a guy in New York to buy the special part and core charge until I returned the part out of my trans.
info@bugat5speed.de
I think it was this part.
Click to view attachment

Thank you for responding to my thread. At this point I am not sure what direction I want to go in. Based on the cost for the conversion and the inability to have a qualified shop do the conversion in a timely fashion I may just stick with the 901. The reason I reached out is I need to change the clutch and thought this would be a good time to do the conversion. If I do decide to move forward with the conversion I would prefer to use an aluminum case 915.

The 915 trans conversion is a bit of a project and almost every part differs from the 914 trans. I’ve you currently have a good 914 trans, getting the car on the road and then doing the 915 conversion later wouldn’t be the worst thing in the world.

@Mepstein - I absolutely agree; if I embark on that project, it will definitely be after the 3.6 is in and everything else is totally sorted. But I have thought about it.

That would be smart for now. I wasted money on two expert 915 local Porsche shops that could not make my Martin Bott 916 shift correctly. When your ready, IMHO I would ship your trans and 916 kit to Patrick Motorsports and have them build it. They also resell the Martin Bott kit. They also sell the shift linkinkage, clutch parts, etc for a turn key setup. Unless you know of a shop that has done it with references, then I would stay away from them.

If Peter wasn’t so busy, he’d be the go-to shop on the east.
I just bought a G50 from a good friend of Peter’s who is pretty much his transmission protege. I’ll be up there next week and ask him if he’s done any. We build 901/914/915 but send the g50/964/993 etc. to him.

Here is a Genuine 916 trans for reference

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