What Gearbox can fit my 74 2.7????

[madmanzippy]

Hi all, Have to admit I have just been a long time reader of this amazing site and now my beloved 74 2.7 has started to cause me serious problems. I am not sure of the gearbox it has in it, i believe it is pre 70's as it is 4speed with the reverse being left and forward. The other day I went for 4th and the lever got stiff as i changed, I got home with only 1st and 3rd left available. I disconnected the shaft (inside the car) and the gear lever moves freely, so this must mean the fault is a fork or something. As gearboxes are so pricey here for the 911 I was wondering if a 6speed boxer one would fit? What options do I have? I don't mind having to make an adapter plate. Anyway it has been a bit noisy on I think the final drive for a couple of years over about 70kmh so would at least need a recondition on its current gbox.

Any wisdom would be very much appreciated.

Thanks
Nick

[Oh Haha]

While certainly possible, installing an "updated" gearbox will cost some good $$$

There is alot of work modifying the chassis to accept them.

Why not see what exactly is wrong with your gearbox? It may as simple as needing to adjust the linkage or replace the shifter bushings.

Did you move the gear selector rod while it was disconnected from the shifter linkage?



Lastly, where are you located? Pelicans are worldwide and I'm sure one us would be willing to help you with a diagnosis.

[Bill Verburg]

Originally Posted by madmanzippy

Hi all, Have to admit I have just been a long time reader of this amazing site and now my beloved 74 2.7 has started to cause me serious problems. I am not sure of the gearbox it has in it, i believe it is pre 70's as it is 4speed with the reverse being left and forward. The other day I went for 4th and the lever got stiff as i changed, I got home with only 1st and 3rd left available. I disconnected the shaft (inside the car) and the gear lever moves freely, so this must mean the fault is a fork or something. As gearboxes are so pricey here for the 911 I was wondering if a 6speed boxer one would fit? What options do I have? I don't mind having to make an adapter plate. Anyway it has been a bit noisy on I think the final drive for a couple of years over about 70kmh so would at least need a recondition on its current gbox.

Any wisdom would be very much appreciated.

Thanks
Nick

A '74 should have a 915 gearbox. They came in both 4 and 5 speed versions. While an earlier 901 or even a later g50 5 or 6 speed could be fitted it is going to be very expensive to do so.

I'd take it to a shop that know Porsche and 915s, you will be best served by rebuilding what you already have or replacing it w/ a 5 speed version, these are going to be the cheapest and best options for you.

[RWebb]

there are some updates & strengthening things you can do - I like the Mg cased 915s -- not as much as a typ 911, but...

Grady has posted on the dam seal - you can search using those terms - also find the best tranny thread

5 speeds are better than 4 - $$ issues are up to you

post the # on the bottom boss of the trans. case

address the CVs& shifter bushings at the same time

[madmanzippy]

Thanks all. I thought i would check as I have done swaps with various other cars over the years and it hasn't been too bad.

I did disconnect the gear lever from the shaft. this then allowed the gear lever to move freely, however at the gear box end it was still all stiff. This car is a bit of a mix I think as it has two vin plates. I know it was originaly a 74 911T but the previous owner said the body was shot and picked up a rolling 79 shell ex Japan.
Numbers on the box I wrote down ages ago are 911/00 and 7010154 not sure if this gives any idea on what it is.

I am in New Zealand so parts aren't too easy or cheap to come by and as for mechanics I only know some of the performance or mainstream guys and you need to mortgage your house to just walk into the workshop. So if there are any Kiwis out there willing to help me or do a cashy let me know, I am in Mangawhai but could always meet in Auckland.

I would love to do it myself, but absolute hectic life currently (and this car is my daily driver) I think It would be best to work alongside someone who knows what they are doing so it could be sorted quickly.

[madmanzippy]

Thanks all for the replies.
I have done some investigating with disconnecting shafts and testing where it is stiff which is why i think it is the internals of the box.

I have swapped a number of g/boxes on other cars over the years and it wasn't that hard. I am located in New Zealand and the only places I know of for servicing Porches you need to mortgage your house to enter the workshop.

Some numbers I got from the box ages ago are: 911/00 and 7010154. I know this car is not original as the prvious owner said it started life as a 74 911T then due to rust it was reshelled with a rolling 79 shell from Japan. Nice thing is the vehicle certifiers have allowed both vin plates to remain on the car so I have at least some traceable history. So if anyone can let me know what this box is, it would be much appreciated

My life is absolute madness at the moment and with this car being my daily driver I don't have the time to use this opportunity to learn from. However I would love to find someone that would work on this with me and show me how it's done, as I believe you get a lot more satisfaction out of doing it yourself rather than just throwing it in the shop. So if there are any Kiwis that are keen for a private job let me know. I am in Managwhai but don't mind travelling to Auckland.

Or I could be open to someone sharing shipping of some bits and pieces from either UK or US.

Thanks guys

[Grady Clay]

The transmission is a 4-speed type 911 from models 1970 and 1971 available on 911T, E & S (usually 911T). It is the 154th 1971 model.

That is a relatively easy transmission to work on. It is virtually identical to the 901 from 1964 on 911 and 912. It is also almost identical internally to the 914 transmission.

To get you back on the road soon, repairing your transmission should be simple. Search Pelican on keywords “901”, “transmission”, etc. as many have been repaired.

If you need internal parts, good used pieces should be available (even by air from the States). I can’t imagine the duty on “used transmission parts” to be too much.

We can help you through this ‘step-by-step’.
EDIT
We will have the only Porsche Transmission Expert in the metropolis of Mangawhai, Northland, New Zealand.


Once back on the road, we can help with the decision to replace the existing transmission with something more fun.

What engine is in the car?
What plans do you have for ‘improvements’ or another engine?

Best,
Grady

[911st]

So it sounds like might be a 901 box. Your car came with a 915. Thus ether one should be and easy change over.

No reason to go beyond a 915 box for a 2.7 unless you have something freakish planed like a twin turbo.

Some prefer the gear layout of the 901 box. It is also lighter and may or may not have better gear ratios for a modest HP motor.

I suspect you have a mechanical speedo. I am not sure which years have this but probably a 72-77. Not sure.

I would stay away from the 72 915 box. I think it had the shaft seal on the inside which meant you pretty much have to take the box apart to replace it.

There are also different CV flanges. I suspect they changed with the 78SC.

Also, there was a rear differential gearing change around 77. Good for freeway cruising, not so good for off the line acceleration.

I believe you will need to change the flywheel to go back to a 915. Your flywheel might have value to a 914 guy building a 914-6. The 73 or newer 915 shifter is different to. Probably a different clutch cable set up to.

Thus, probably a 73-75 transmission might be a best option if you want to update to a 915.

Maybe someone that knows transmissions could double check my points.

[RWebb]

'73 915 has some detriments -- check the best trans. thread before buying anything

if you get a 915, the '76 or '77 may be best, followed by the '75 - all can be strengthened if you hot rod the motor

I prefer the road racing shift pattern and light flicking gear changes in the 901 & 911 boxes -- NZ has the perfect uncongested road system for such a shift pattern, unless you never take the car outside of Aukland or Christchurch or something weird like that...

is the car kept & driven near Mangawhai?? I'd never use a 915 on fun roads, unless they are all 3-4 shifts (high speeds) & I've never seen that in NZ, tho not familiar with your area.

[Grady Clay]

This is what makes Pelican so much fun (and valuable for everyone worldwide).

Mangawhai, Northland, New Zealand - Google Search


Mangawhai, Northland, New Zealand - Google Maps

I can sit here in Denver and fix a type 911 transmission in Mangawhai with the help of experts everywhere.

I suspect we can find every part necessary and ship as Christmas presents to our fellow Pelican.

Since the goal is to repair a ‘daily’ 911, I suspect it will be an early summer (South of Equator) Christmas.

Best,
Grady

[RWebb]

more info for you:

Best Year for a 915 Transmission?

somewhere there is a table of 915 changes - apparently I did not save that thread

[911st]

If me and I wanted to go back to a 915 with the lower rear R&P, mechanical speedo, and correct CV mounts for the year, I would be looking for a 74/5 box.

Here is the meat from Webb's link that I am basing this on:

Originally Posted by randywebb

...

1972,3,4,5 will give you 7:31 CWP ratio

1976,77 will have 8:31 CWP ratio

1972 has the input shaft seal installation flaw.

1973 (april on) has an improved input shaft seal installation -
although effectively still a fixed guide tube.

1974 has the removable guide tube - for bench top input shaft seal
replacement.

1972,3,4,5 will give you a cable drive speedo

1976,77 has electric speedo - can not be retro fitted with cable
speedo without significant parts.

1972,3,4,5,6,7, are all magnesium, 1977 (915/61) are also available in
aluminum, with the case material being the only variation.

Sometimes overlooked when installing a 915 in a 901 chassis, is the
main shift tube. At a glance, they are similar, but the 901 component
is 15mm longer than the tube used for 915. It's trapped in the car
once the transmission is installed, so needs to be exchanged prior to
engine install.

Regards

Hayden

WEVO
__________________
Technical Director
Windrush Evolutions Inc.

...

However, a good used l901 5 speed should slot right in the place of your existing, be lighter, might be cheaper, and might have better gear ratios and be faster. FWIW.

Good luck.

[Matt Monson]

The 4spd 911 mag box that's in there now has some really goofy ratios in it. It's A, HB, S, Za if memory serves. That 2nd to 3rd shift is probably no fun at all.

Zippy,
How and where do you drive this car? I might be game to toss a gear or two your way and join on Grady's Christmas party depending on if I've got some spares that would be a good match for your needs.

[madmanzippy]

All I can say is, WOW thanks guys. Your offers and parting of wisdom is re assuring. I do find the 2nd to 3rd shift a bit to wide, however over all i quite like the 4spd as it tends to not allow too much loss of traction due to too much torque yet gives you a great 3rd gear for NZ roads. I try and keep out of Auckland driving however I do get to enjoy the drive between home and Auckland regularly.
I am currently building my garage at the moment and we are shifting into our new place in a couple of weeks time, which I am still rewiring, building a kitchen and painting, this is why I say my life is hectic. I think I may just have to borrow a car for a few weeks, this will allow me to get the family into the house, then worry about the car. It will also give me time to source a few parts, cause the box will be open it seems crazy not to give it a birthday.

As for future plans for it: The warmer weather is kicking in and I have got new window rubbers for it, I want to pull all the glass and give the car a respray before summer. The body is in good condition, just a bit of a tired paint job. The engine seems good at the moment and it checked out well when I bought it 2 years ago so for now I will just keep on looking after it and enjoying it till needs must. I will keep my eyes out for a good 3.0L + engine as the 2.7 is a tad under power and just seems like it's a bit flawed.

[911st]

Pic's?

[Grady Clay]

I agree. Some good images from Mangawhai are desired.

Critical here is how your type 911/00 was installed in your ’74 chassis. Are the clutch operation parts exactly as a ’70-’71? This is critically important as the type 911 transmission has a transition from type 901 push-type clutch to the 915 pull-type clutch with some unique parts. These are two-years (’70-’71) only.


Can you find a serviceable ’68 or ’69 5-speed 901 transmission locally?
These have the parts to convert your 4-speed to 5-speed and get the most desirable gear ratios (AFMSX) for fast travel between Mangawhai and Aukland (looks like a great road).

Among Matt, I and others, I’m sure we can get you back functioning soon with your 911/00.

While your ’74 originally had a type 915 transmission, the type 911 can easily handle your 2.7, even in hot-rod form. If you change to a 3.0 and larger, I recommend converting back to a 915. The above recommendations for a mag-case about ’75-’76-’77 are correct.

Please post your garage progress.
We all have the same lust for more garage space.
I’m in the same process.

Best,
Grady

[madmanzippy]

Hi all,
Well it has been a long time since I have posted or anything. In fact this is the first time in a year ish that I have visited pelican.

After the box issue, we had house issues. We had a house moved onto our section and it got wet and went horribly wrong and involved lawyers and threats and stress at the same time as I was starting my own business. So to say the least I have been a little busy. My poor baby got thrown in the garage and not quite forgotten about, more like, one day I will fix it.

Well the time came the other day to give it a good run. After taking it for a good blast around some unsealed roads (as best I could with only 1st and 3rd), it is going to get done. However I would prefer to just buy a box from the states and ship it and fit it. Although I probably could repair it myself, I spend too much time getting the business going to worry about this.

So I am asking if you guys know of any good boxes for sale that would be suitable. As there are so many wise people here it is better than trying ebay and gambling with what I end up with. I may even entertain the thought of motor and box if it is a great deal. Or even a whole car????

Anyway if someone is willing to sell me a gearbox with some good ratios for twisty hilly roads would be ideal.

Thanks for reading and I appreciate any help.

Cheers
Nick

[madmanzippy]

Sorry for never getting back with photos. Here is a link to a site that has some great pics of the place. It is a place with a permenant population of about 1600 but has 10's of thousands visitors over the peak holiday season. Nice spot to relax when you can.
Flickriver: Photos from Mangawhai, Northland, New Zealand