Have you seen a 915 tranny swap thread?, With pictures would be great. Options

[Twystd1]

OK,

I screwed up on another board and gave very incomplete data to someone.

I can't find a 915 swap thread using the search function.

I am looking for a thread that explains ALL of the issues with this conversion.

If you guys know of any thread on any board.

Please let me know. I really want to help this guy get it right.

Thanks fellas,

Clayton

[Twystd1]

McFly?




C

[Twystd1]

Z...

You ever done this?????????????

[914-8]

I'm doing some work on my 915 conversion right now, have it out of the car and apart, so I've become very familiar with it. What issue are you looking at? There are quite a few. None are a huge deal, but they do kinda add up.

You have to have a way to mount it and to shift it. There's the Vellios kit and the Wevo kit to do that. It can be linkage shifted, you need to have a customized shift bar to do that (the angles have to be right). Or it can be cable shifted, but I wouldn't personally do that, at least based on the discontent I've heard from a lot of cable shift setups. With a stock style linkage/bar setup, my 915 in my 914 shifts just like my 915 in my 911.

You need a custom/modified pulley system for the clutch cable. You have to flip the RP. You have to adapt axles, but there's a lot of ways to do that. My 915 is from a '78 and is electronic speedo, I'm not 100% sure about the earlier ones, but I think they are all electric, so in a 914, you need a new speedo. Since it's driven off the RP, you also need to machine something in the case to relocate the speedo sensor.

From what I can see, that's it.

The 915 is a very good transmission, capable of holding a good amount of power. The only semi-weakness is 2nd gear, and 2nd gears only weakness is when you powershift into it (shift quickly then apply full power very quickly) with a lot of HP (say high 200s to 300+). If you just take it a bit easy on the shifts into second, it lasts a long time. The only real upgrade you can do to it for a 914 application is the Wevo bearing retainer, which harnesses the input and pinion bearing shafts together.

[Twystd1]

Thanks for the info..

That is great data....!!!!!!!!!!

Part of the problem is that I am lazy... And I don't want to write a 6 page essay on how to do it. Just takes to dam much time.

The data you just gave was very helpful. I hope more data will be coming forward to help this fella.

Lets see how this goes..........

Clayton

[Hoss]

... I hope more data will be coming forward to help this fella.

Lets see how this goes..........

Clayton

Clayton,

You should ping Kevin (kdfoust) since he is in the process or has completed his 901 to 915 swap. He may be able to help you with the Cliff notes on that beast.

Cheers.

[Twystd1]

will do...!!!!!

Keep it coming fellas...


C

[Crazyhippy]

Nicely stolen from Renegade Hybrids webpage

The BIG Tranny Swap

915 or 930 transaxle in a 914 chassis? Decide for yourself.

By now, you have probably been well educated on the limitations of the stock 914 transaxle. If not, here is a quick recap...

1. Don't use 1st gear period.

2. 300 HP and 300 FPT are the streetable limitations.

3. Shock loading will kill the tranny in no time.

4. No speed shifting or excessive abuse.

5. Have your 914 tranny converted to a four speed with taller gears by Renegade if the following scares you!

If 300 HP is not even close to what you had in mind for your 914, well... you might want to read what it takes to go really big!!! Don't get me wrong... We have many customers that choose the upgrade after they have gone through a few stock 914 transaxles, but it take a pretty hefty contribution to the conversion God's to afford this conversion done correctly.

Let's first consider your transaxle of choice. The 915 is easily obtainable but it really only increases your HP and torque capability a little. I would push the 915 to about 400HP and 350FPT, before your odds of failure increase greatly. Plus, the stock 915 gear ratios are really quite short and very close together. For a V-8 conversion, your final drive (5th gear) puts your cruising RPM's at over 3000 at 70 MPH in most cases... and your first gear is so low that it is virtually unusable.

We do have a taller 3:10 ring and pinion available for the 915, which makes that tranny really excellent for a V-8 conversion, but the cost is rather high, and the availability of that custom ring and pinion is minimal at best.

NOTE: The 3:10 ring and pinion is no longer available... sorry. (9/1/2003)

By the time you invest in the 915 with the taller ring and pinion, a tranny rebuild, the clutch components, and all the other bells and whistles, you might as well consider the 930 turbo 4 speed trans from a 911 turbo!

The 930 is quite the excellent choice for the 914 conversion for many reasons, but there is a lot to learn before you race out and grab the first 930 you find.

First of all, the good stuff. 700HP and 700FPT are not a problem with the 930 trans. The stock gear ratios are just about perfect for a V-8 conversion. Tons of custom gears and multiple high performance upgrades are available. The giant 240mm clutch components are excellent for high HP applications that still require "streetability." The ring and pinion can be flipped to run in any mid engine application. ...And the list goes on.

The drawbacks are fewer, and most are easily rectified. With the following brief history lesson, you will see the pros and cons of this workhorse of a transaxle.

The first two years of the 930 turbo trans ('76 and '77), the length was one inch shorter than the years to follow. The early 930 chassis was very similar to the 911 NA design, because the trannies were about the same in physical dimension.

Porsche used a typical pull type pressure plate, like the 915, with a greater surface area, and that was quite adequate at first. However, with the rapid increase of HP in the turbo motors, slippage became an issue by the very late 70's. Because high performance materials available for the clutch disc surface were quite limited and rather temperamental, the only solution to getting more grip with smooth engagement was to increase the clamping force of the pressure plate. So Porsche added approximately one inch to the 78 and later bellhousings so that a thicker/stronger pressure plate design could be implemented.

This also made the chassis designers go back to their desks and look for some more space under the back seat for the bigger tranny. The compromise was to move the transaxle forward a bit, and skew the rear motor mount back a little, to accommodate the longer motor assembly. As Mike would put it... "It's like putting 10 pounds of crap in a 5 pound bucket!" It was tight.

In the years to come after the introduction of the early '76 and '77 930 transaxles, the 911 NA racers started grabbing up any early boxes they could find and installing them in their 911 chassis. The later '78 and up 930's, were to long to fit in the 911's so the box of choice was this first generation turbo trans. If you were lucky enough to find one of those two year only trannies today, you might find it to be quite tired and stressed.

Well, guess what? That short 76/77 early 930 box, is the only one that fits perfectly in the 914 with minimal increased axle angle. Since this tranny is not easily available, we have developed a method of shortening the longer (late model) bellhousings and the main shafts to accommodate the 914 mid engine application. But, there is a trick to doing this that can make this seemingly easy process a difficult mess.

Unbeknownst to most Porsche enthusiasts, the 930 came in three versions... not just two. If you look inside the bellhousing on a 78 to a mid 80's 930 transaxle, you will see the four bellhousing through-boltholes are not reinforced so you can see the exposed bolt pass through the inside of the bellhousing. This makes this second generation 930 a poor choice for the modification without welding a lip around the mouth of the shortened bellhousing once you have made the cut. If you have ever tig welded to a casting, you know that is a very difficult process.

The late model 930 bellhousings are a different story. At about an inch back from the stock bell, there is a rib that circles the mouth of the bell and the through-bolts are covered by the updated casting within the bellhousing. This provides the lip that is needed to securely locate the tranny to the adapter plate. Here is the catch... The newer the 930 tranny, the more the price of the core.

But wait... There is more! A lot more.

The flipping of the 930 ring and pinion is quite the miracle if done correctly. Not only do you heavily modify the internals of the case, but you also have to add extra support adjacent to the main shaft which is evident just below the guide tube inside the bell. There are very few Porsche tranny technicians that even get close to doing this process correctly and can maintain the high HP and torque capabilities. Let's not forget the electric speedo modification to relocate the electronic pick up after the ring and pinion is flipped.

Enough about the tranny... How about everything else! It's easiest to just give you a list at this point... and I am quite sure I will leave a few things out!

You have the Renegade clutch components with a high performance pressure plate, custom flywheel, Kevlar clutch disc, custom pilot bearing, throw out bearing, and hardened ring gear.

Then you need a Renegade custom cable shift kit that usually runs around 90 inches in a 914. It's a particularly nice unit, but if you would like to finish off your interior around the gate shifter, a custom center console is recommended.

Then you have the Renegade custom pivot wheel and cable extension assembly, which allows the stock 914 clutch cable to be used with the 930 tranny. This usually attaches to the 930 clutch arm-broached finger-omega spring-bracket assembly, that never seems to come with the tranny when you find one. All of this stuff is strictly Porsche, and is very hard to get.

How about axles? You will need Renegade custom length axles with 930 inward CV's and 911 (very rare) 4 bolt and two roll pin outward CV's. Your stub axles are also 911, but they need to be the larger diameter face with the 4 bolt and two roll pin provisions, but still have the 914 axle spine. Don't forget to have the rear hubs drilled to accommodate the five studs for your five lug conversion. We do it all.

Since the 930 has no ears on the rear housing like the 914, a custom Renegade rear trans mount bracket is the next on this list. The stock 914 rear tranny mounts are really unsafe at this point, so a pair of modified 911 sport style motor mounts actually work really well.

Your stock speedometer is cable driven, but your tranny has two wires sticking out the side of the case. It's time to get a new 911 style electronic speedometer.

Some good news! Your current adapter plate will work as long as you have the thicker style... AND, if you have used a gear reduction style starter on your conversion before your tranny upgrade, it will still fit and operate correctly in the 930 starter pocket.

The damage??? Are you sitting down? You will spend over 10k on the tranny and related transaxle conversion parts, and that does not include ANY of the V-8 engine conversion parts! That is for just the tranny and all the related systems that make it work in the 914.

Back to the 915, you might save about $1000 at best over the 930. It's not worth it. Go for the 930 if you plan to do it at all.

Don't get me wrong. If you consider your 400+ HP 914 car, with the complete 930 tranny conversion, can out perform cars at 5 times your investment, this is quite a bargain. We have sold a ton of upgrade kits and 930 turbo trannies through the years with not one of our customers wishes they still had the 914/901 tranny.

On the other hand, if you can keep your motor down under 300 HP and 300 FPT, and your driving might be considered a little on the conservative side, the 914 transaxle might just be the box of choice.

If you have any questions or comments, please feel free to contact me in the office Monday though Friday. Thank you!!!

- Scott

BJH

[Joe Bob]

Z...

You ever done this?????????????

Nope...I think a 915 exchange is a waste of time. 930 or G50 if you are gonna go to the trouble. The 915 has it's weak points and they are many.

I would keep a 901 over a 915 anytime.

[Twystd1]

Thats very interesting Mike.

Care to give us a little more info?

C

[Twystd1]

{EDIT}

It's Aarons fault I double posted.... dam kid.............

C

[914-8]

As far as transmission choices, I think it depends on what you are intending to run it behind, what power/torque you are going to run, where you are starting from, what your goals are and your budget.

[dr914@autoatlanta.com]

Having both a 914 issued from the FACTORY with a 915 transmission and one next to it with an aftermarket 915, I would NEVER have anything but a 901 in my 914-6 (of course this has nothing to do with the V something conversions)

We worked a long time to make the 915 shift as perfectly as possible in a 914-6 and retain its original look. To begine with the wevo intrudes upon mounting ANY muffler on the car so it is out! The vellios is an old casting and has to be massaged with a little machine work for a more precise shift. Using it also means an electric speedo and pickup cut into the side cover as when the ring gear and pinion is swapped the pickup has to go on the opposite side. We experimented with moving the clutch roller assembly sideways for best operation but dumped it in favor of our custom made aluminum part that allows a pull clutch, eliminating the roller assembly while still using the 915 helper spring assembly and pedal 911 pedal cluster with helper spring. These are necessary for a reasonably pressured clutch release. The 915 also has to be spaced down as not to hit the trunk floor, and 914-6 transmission mounts are used. The shifter is another matter: Jim Patrick makes his own shift kit that is a serious departure from any factory piece, but we use a conventional setup that includes all bolt in parts and two parts fabricated from factory parts. They include a stock factory short shift (NOT aftermarket SHORT SHIFT!!!!!!) 70-72 tunnel bar, front 70-72 shift adjustment collar welded to the end of a 73-76 tunnel bar, and a rear 73-76 bar perfectly straigtened to 39 ''. The cv axles are the stock 914 ones and bolt right in with no modification. This setup bolts perfectly into the vellious 916 transmission conversion, and shifts the best we could EVER achieve, allowing one to shift very quickly and precisely at track speeds. This setup also necessitates the use of the rich johnson bulkhead mount as the so called "quick six" mount does not allow for the shift rod to be removed without lowering the engine!!!!!
Conclusion: Clutch works very effortlessly, transmission shifts smoothly and quickly, the electric speedometer is accurate, and the original 73-76 914 transmission and shift linkage is still superior!

[Joe Bob]

Thats very interesting Mike.

Care to give us a little more info?

C

Well first off the shafts flex, the intermediate bearing can oval out and second gear explodes....WEVO makes a shaft/intermediate plate that ties BOTH shafts together....the 930 and the G50 have that from the factory.

[bondo]

What's it take to put a G50 in a 914? Doesn't seem like a very common swap, but I don't know the details. All I know is that it has to be run upside down because the R&P can't be flipped. Are the ratios decent for a V8?

[Crazyhippy]

G-50 factory ratios are ok... not perfect, but not bad. the 930 has some great v-8 ratios, and the v8 has enough tq to cover the gear spread w/ ease.

BJH

[bondo]

G-50 factory ratios are ok... not perfect, but not bad. the 930 has some great v-8 ratios, and the v8 has enough tq to cover the gear spread w/ ease.

BJH

Which has the taller top gear? The T-56 in the car my V8 came out of had a nice 1600 rpm freeway cruise. (and it could still pass without downshifting into 5th) (IMG:style_emoticons/default/biggrin.gif)

[Aaron Cox]

talk to mugs 914....

he put a g50 in his race car....

the sucker is long.. and with a cable shifter.. slightly protrudes past the bumper....

oh.. and you gotta run em upside down from what ive read

[Crazyhippy]

G-50 factory ratios are ok... not perfect, but not bad. the 930 has some great v-8 ratios, and the v8 has enough tq to cover the gear spread w/ ease.

BJH

Which has the taller top gear? The T-56 in the car my V8 came out of had a nice 1600 rpm freeway cruise. (and it could still pass without downshifting into 5th) (IMG:style_emoticons/default/biggrin.gif)

Not that tall... and i have to look to see which is taller stock. Enough motor and a 930 trans @ 7000rpm is faster than a mild mod GSXR750 (IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/confused24.gif) (IMG:style_emoticons/default/clap56.gif) (IMG:style_emoticons/default/happy11.gif)

3K rpmish will get you from Vegas to Hollywood in just over 3hrs too (IMG:style_emoticons/default/unsure.gif) (IMG:style_emoticons/default/thumb3d.gif)

BJH

[GeorgeRud]

There's a fellow (Derick) that has a 904 recreation he's working on (P904@shaw.ca). He has a 930 box with the Vellios conversion for sale for $8500, a good price in my opinion considering the steps you have to go through.

Dr. 914s comments on the 915 conversion seem quite right on. I used the Vellios conversion on mine, and had similar experiences. The 915 does shift nicely now, but I used a 915 shift tower, custom made linkage from metric sized metal tubing, and a nicely converted transmission. All the items can be taken care of pretty easily, and even the clutch cable works OK. I used the 90 degree adapter from Patrick to change the orientation of the pulley to horizontal.

A billet side plate with a mount for the electronic speedo sendor would be a nice part, but I used the standard one with a machined area between two stiffening ribs to mount the sender.

The Vellios tailpiece seems to take care of the spacing, as my transmission fit without any clearance issues. I also used the WEVO transmission mounts to help the shifting, and a Rich Johnson front mount.

I used an early (1975) 915 transmission, so I had the course splined output shafts already. I simply had to swap them for the 914 ones, and the axles were taken care of. I have been slowly assembling the necessary parts to go back to the larger CV jointed axles, but that's for a future project.

Another minor point is that you have to come up with some way of switching the backup lights as the 915 doesn't have the required boss on the side. I mounted a microswitch to the transmission, and an activating lever on the shift rod itself.