mxracer21cb

Hey,
I have a 1968 911 L sportomatic. What transmission from what porsche could I switch to turn the sportamatic into a full manual? What tranny does everybody like and seem to be bullet proof? Thanks a lot

PS the engine is a 2.0 6 cylinder

thanks
chris

Noel

I've heard of 915 trany conversion for that car. The 915 is a very reliabe tranny and you could find a used one fairly cheap. Very strong but fragile. It will not tolerate fast shifting, but last 100K+ miles when maintained properly.

mxracer21cb

Noel, thanks a lot. How much could i get a used one for and then how much would it cost to have it rebuilt? Do you know of any more aggressive trannys i can interchange with the car?

LukeSportsman

For a 2.0 I would go a for a deep geared mag cased 915 with a 73 or later shifter. What type of pedal cluster do you currently have? A 901 is a lot cheaper, but most parts don't cross over and you'll need to learn the dog leg shifter. If strength is of concern and a little weight won't kill you, I'd stick with 915 and this would allow for more upgrades in the future.

Probably have to change out crossmember. I would obgrade to later crossmember and this has been covered before. Then you can use the much more affordable mounts.

The ideal setup, I would think would be a 7/31 close ratio geared 915 with a stock clutch setup. I would stay away from a lightweight flywheel if for street use in a 2.0. If go to later 915 you get less gear, heavier Al case, and have to upgrade the speedo to electric. I have no idea if you'll have to upgrade the speedo in all case anyway since I unfamiliar with your setup.

LukeSportsman

I would consider John Walker's shop to rebuild mine.

If you want aggressive and stay with a Porsche setup...just open Excellence for advertisements. Several options with dog tooth'd and drilled gears. Close ratios designed for just your power/weight setup.

If you want to go crazy, and I would remove the 2.0 also at this point, would be sequential shift Mendeola transaxle. 5-6 speeds without a clutch on shift....$15k plus fabrication, but owe it would be IMSA cool and unbreakable.

Seriously, a 915 that is mod'd will provide a great trade off of money/weight/performance/ease of installation and support.

mxracer21cb

thanks luke, so what how much am i looking at to get my hands on a 915 and rebuild it. What parts would i also have to change up to match the 915 and how much would that run me? Thanks a lot, im a 17 year old rebuilding this car and am not very familiar with porsche trany's any help or advice is appreciated.

LukeSportsman

Chris,

What are your intentions for this car? By the way, great choice of cars to restore for a 17 year old.

I've never converted a sportomatic, so take all advice with hesitation from me. There is always great tech advice offered here and a little more action in regards to 911's on Pelican.

1. Check for flywheel differences? I would think that you'd need to change over to a later 915 designed flywheel/clutch/pressure plate setup. Get NEW flywheel bolts. You'll need two special tools: 8mm and 12mm internal wrenches from say NAPA or the like ~$25. You might want a flywheel lock tool ~$30.
2. You will need a new throwout bearing assembly ~$115
3. You will need a cross member and two later style mounts ~40 each on mounts, talk to some shops and look at classifieds for crossmember...search for converting early to late crossmember. Early mounts are quite expensive and not superior.
4. Obviously the 915 tranny that could be sourced from several people, the likes of UncleZak's or a Vertex if rebuilt is prefered ~$1500.
5. Don't believe unless SERIOUS racing is in your immediate plans that a limited slip diff is in your plans or needs with 2.0 ~$1200.
6. 73 or later shifter....look for used. WEVO is $1k+ and rebuild the bushings which is not expensive and relatively inexpensive.
7. Shop manual $1-200 used...out of print for early cars. Check swap meets
8. If your willing to buy parts, John Walker is a very honest and helpful person with more tranny knowledge in his one finger than me.
9. Pedal assembly: call some shops that do conversions. G50 conversions need a whole different setup and may have older setups available. Of course part warehouses that break Porsches will have these parts, but tend to ask more.
10. Proper cables and ends
11. axle ends will likely need changing/upgrading couple hundred new, probably sourceable gently used.

Ask more questions and spend time on the forums. These are great fun and I think as the years pass, the trouble and cost will be offset by the appreciation you learn. Your buddies will have faster Civics, but they will be torn up and passed by in just a couple years. You have a time capsule!

r911

Note the drive flanges on a 915 will not fit the CV joints on a '68. You cannot change the trans. drive flanges and cannot change the CV joints on the half-shafts. It is a hell of problem to make this work. A machine shop can do it - but they aren't cheap.

LukeSportsman

How about using some of the "dune buggy" guys? They seem to make conversion axles for all types of arrangements. Look in Sand Cars or VW type magazines for some references. I'm sure someone can do this...look at some of the "Kit Car" industry (they are not all flakey these days).

pjc

This modificaton has been pretty common in the UK but written communication with Bruce Anderson some years ago suggested it was too expensive for folks to do it the USA. If you intend keeping the car then it seems a worthwhile exercise (if you can't live with the Sporto system) but if it is 'just another car' and will be swapped in in a few years could be a waste of money and you may be better off waiting to spend your bucks on something more worthwhile - particularly if you have to pay a shop to do the work.

PJC

r911

How do they adapt the drive axles in the UK? Is there a source of ones that have splines to fit his half-shafts, but flanges to fit the newer trans.? If so, he could think about the $$ and trouble to import them.

You also might try posting this on Pelican. I know a couple of racers have done this mix and match thing with certain trannys and engines.

My project is to put a 911 type trans. (1970-71 ones, sometimes called 901 tho the p/n begins with 911) onto a 3.2L engine and put it all in a 1973 911. I spent a lot of time finding out how hard it is with a true 901 trans (up to 1969). In contrast, the 911 trans. will bolt right onto the later CV joints. So I hope I've saved you a few hundred hours of frustration -- that's what I spent on it probably.

mxracer21cb

thanks for your input? what is the name of the manual tranny that is on a manual 68 911? Shouldnt they half shafts fit those? Is that the 915 or 901 or something else?

thanks again

r911

901 - up to end of '69
911 (often called 901) - 1970-71 -- stronger evolution of 901; has same output flanges as 915
915 - 1972 to about 1986, stronger, heavier than earlier ones
G50 -- different synchros, stronger, heavier than 915

spyderman

hey, just noticed your thread, and thought id share some of my advise,
firt off, i would deciede what you want to do with this car? is it a somewhat stock restoration? if so dont go with the 915 trans, there are too many mods that have to be made, and they arent worth doing if yoou are planing on doing a stock, or mildly moddified restoration. stick with a 901 trans that originally came with the car. it is a much eaiser and less expensive swap, and you can use original equipment parts. Ive noticed that sometimes the guys on this sight get kinda wacky with the advise they give, and really dont think about what the owner of the car is trying to accomplish. ive done a few sport-o to manual conversions, and there not hard to accomplish but if your just restoring it, and not building some crazy race car, then i would stick with the 901 trans instead of the 915.

r911

also there is an Al piece that strengthens the 911 trans. I don't know if it for the 901 also. Steve Wiener does that work, I think - and he has posted on it.

Another item to consider: why give up the road race shift pattern? Are you commuting in the car in stop & go traffic? The early shift pattern is superior for open road use....