Which gearbox would you recommend?

[Jim Richards]

If you were looking for 912 used as an occassional driver / fun car for running around, would you choose the 4-speed gearbox or the 5-speed?

[craign]

Jim,

5-speed, every time I drive it I wish I had that 5th gear.

Craig
69-912

[Duke]

Every 912 should have the 5 speed. You will need this for any driving in hilly or mountainous terrain.

[C. Clark]

Were I live in the mountains of Mendocino a 6 speed has crossed my mind several times, but alas a 5 will have to do.
Chas.
69/912 coupe

[dimps8]

5 SPEED IS GREAT. EVEN THOUGH YOU NEVER USE 5TH AROUND THE STREETS OR MOUNTAINS ETC, THE 5 SPEED RATIOS ARE CLOSER THAN THE 4. MAKES FOR A LOT OF FUN!!!!

[Jim Richards]

Thanks all for your views on this tradeoff. It sure seems pretty one-sided in favor of the 5-speed. I've seen some nice looking 912's for sale that have 4-speed gearboxes and the sellers seem to ask the same price for their cars. Should they / do they sell at similar prices to 912s with 5-speeds? What would be involved in swapping/converting a 4-speed to a 5-speed, and what would be typical costs for this? As you can see, I'm trying to decide if it makes any sense to buy a 912 with either transaxle and modify it to 5-speed if it already isn't, or just limit the search to 5-speeds. Thanks again for all your help!

[Griznant]

Switching from one gearbox to the other is really quite simple. Drop the drivetrain, unbolt the trans, bolt up the other box, and reinstall drivetrain. Could easily be done in a weekend with average mechanical ability and a few common tools (except for the 12-point socket for the CV bolts, which you will need to order).

It is the same box, just without one gear. No real physical differences externally.

A used 901 5-speed box can be picked up for $350-$500 in good condition.

I have the 4-speed in my '69. I have not driven it yet (have experience with the 5-speeds in others) but the only thing I can see benefiting you on paper is the closer 1-4th ratios. They share the same top gear, so you won't cruise faster, or at lower RPM unless you change the actual gearing itself.


Later,

G

[Green 912]

Jim, for the planned use a 912 4 or 5 speed will work well. As Griznant stated, the final drive is the same for both. The early C.V. bolts are metric hex. Some racers love to use the late 912 differential as it has a lower ring and pinion gear ratio 6/29 rather than 911s 7/31.

One thing to remember, the 912 (902) 5 speed is different than the same year 911 5 speed. If you use a 911 box (901) then the ratios will be different depending on the box used.

Find out which box is in the car if the 912 has a 5 in it. Some 911 5 speeds have much taller ratios than the 912 5 speed. With a too tall 5th gear are reduced to 3 speeds at the track. First is too low for any track and 5th will have no pull. With no planned track use almost any gearbox will work fine.

I use a 902 5 speed for Summit and a 901/ 15 with a lower 5th gear for tracks like Watkins Glen, Mid Ohio and VIR

[Rick Becker]

Jim, another vote for the 5-speeds. I changed my '68 Targa from a 4 to a 5. The closer ratios are a big improvement on grades. On the 4 you need to wind it up in first before shifting to 2nd to keep in the torque band. The ratio comparisons are on the 912 Registry Specifications page:

http://www.912registry.org/faqs/origspec.htm

Hope you find a great one.

Rick B

[BMC912]

I know when asked to choose most people will say that the 5 speeds are better. But consider the answers to the following questions:

1. In a 0-60 race which is faster?

2. When highway driving in top gear which gets better gas milage?

3. A 912 equipped with which transmission will have a higher top speed?

4. Long term, which transmission is more reliable?

If you answered "always and only the 5 speed" you would be wrong. Most people do not realize that the first gear and the last gear in both transmissions are exactly the same.

This means that the top speed is the same for both the 4 and 5 speed.

This means that the highway gas milage is the same for both the 4 and 5 speed.

Then there is the interesting disadvantage of the 5. To get to 60 mph you need to shift into third. The 4 speed can do it with just two gears. Look at the curves in the drivers manual, the 5 speeds are going to get beat.

Another disadvantage of the 5 speed is that it's additional complexity makes it less reliable.

Finally, the 5 speed shift pattern Porsche chose for the 60s cars is very unconventional. 1st gear almost appears to be an afterthought. (Porsche corrected this problem at a later date). A quick movement from 1st to 2nd is something that takes a lot of practice. Coming back to first is even more difficult. On the other hand the forward gears of the 4 speed are the very conventinal "H" pattern. This pattern is still used today in most standard transmissions, including most 5 speeds.

[atlporsche]

as I remember, with first on the 5 speed being down and left, it was an "occasional" gear, and many cars have done this...particularly race cars, which only used first gear at the start of a race.

I could be wrong...

sjd
in seach of the link.

[BMC912]

I agree with "altporsche" that race cars have put 1st in this location. However, if the location of 1st to the left was optimal than why didn't Porsche leave it in that location? Instead they changed to the H pattern for the first 4 gears when they made the 915 gearbox. I am not aware of many modern mass produced cars, with 5 speed transmissions, that have first in the lower left corner location.

Most 912 drivers are not at the track every day. They have the need to get out into traffic or accelerate from a stop light. A good 1st to 2nd transition maybe useful for these purposes. The 912 is not the most powerful car and we need all the help we can get.

Finally, in the typical SCCA autocross you do not use 5th gear. But there are occasions when you need to go back to 1st on a tight course. Looking for 1st next to reverse is a little tricky.

[Efrain68912]

I imagine that when Porsche switched from the 901 to the 915 transmission that they put first in the conventional spot because Joe Average 911 owner found the traditional pattern more convinient.

[dferlauto]

All that said, there is one thing that is indisputable...If you like to throw your car around from time to time that close ratio makes all the difference in the world...Going deep into a corner only to find that your gears are too tall for that perfect downshift really bites.

[BMC912]

I agree with dferlauto 100%. If I had to choose between a well designed 4 speed and a well designed 5 speed, I would always take the 5 speed.

The real question is was the 5 speed 901 a good match for the 912 and was it significantly better than the 4 speed? If you are truly objective and look at the pluses and minuses it would be difficult to conclude that it was significantly better. But I am also sure that honest people can disagree about this conclusion especially when personal preferences come into play.

[69 Soft Targa]

Hello
Good points made. My recollection is that the dogleg 5 speed is the racing pattern. 1st is for launching only / exiting the pits. The "conventional" 5 speed pattern of the 915 was a nod to the convenience of the customer in stop and go traffic. The negative about the "conventional" shift pattern? Well... I've heard some stories about the dreaded missed downshift. Dropping from 5th to 2nd just doesn't do an engine a damn bit of good.

Cheers

[barlowdo]

4speed vs 5 speed. Hmm - which is better, as I recall trucks have close to 16 forward gears. Now if you like rowing thru gears that seems to be the way to go.

Did Porsche ever make a 5 speed Sportomatic ? As I remember it was only available in 4 speed. I wonder why ??????

I have a 5 speed in my car now but would not hesitate putting the 4 speed I have sitting on the bench in my car. Reason being I hate climbing out of the 86 Jeep Cherokee and into the Porsche only to reorient myself where 1st gear is located.

-Don

[Rick Becker]

We have 3 stick-shift cars in the family, with three different 5-speed patterns. Speaking personally, I really prefer the Porsche racing pattern, even if it's more work in stop-and go driving. The four-gate pattern comes in second. The other has 5th above reverse, ugh!

Rick

[barlowdo]

Which engine would you recommend?

If you were looking for a Porsche used as an occassional driver / fun car for running around, would you choose the 4-cylinder engine or the 6 cylinder engine?

[Jim Richards]

Great follow up question. My wife says our 993 has too much power for her. So, for her, either a 912's 4-banger or an early 911T's 6-cyl would be plenty. I like the power I have with the 993...I guess I'm spoiled.