911 Transmission Upgrades
G50 transmission with solid mounts ready for installation
Installation of late style five and six speed gear boxes can be an economical way to increase value and performance, as is converting four speed 911 turbos to five speeds also utilizing the g-50 series boxes.
Choosing the correct box is first: g-50’s are available with both open and limited slip differentials. The later being more desirable for track and serious street drivers. Of course, the limited slip boxes cost a little more,usually $600-1000. The best choice for the track is still the quaiffe or torsen differential. We can provide this upgrade for an additional $2500. If you plan on this option buy the open differential and save afew bucks.
Ther are several ways to install these boxes into 1972-1986 chassis. The factory installed g-50’s in 1987 and later cars. They redesigned the rear torsion bar tube to allow room for the extra length of the g-50 over the 915 model and the turbo four- speed. One approach is to splice in a tube new or from a donor car. You will need the tube cut out between the frame rails. We have aframe jig to weld the center section in. Proper location is critical for the trans mounts as well as the inner mounts for the trailing arms. You will also need the late style torsion bars,end caps and spring plates. Another approach is to convert the car to coil overs, eliminating the cost of the aforementioned tube update which will cost about $3,000. Coil overs installed are around $1500. Once the torsion bars are out of the way the center section of the torque tube is modified to provide the necessary clearance for the front of the g-50.
The best method for the update that we have found so far is to modify the g-50 to “bolt in”this is done by machining the bellhousing and the mainshaft. This, along with a modified mount will allow the box to bolt into your existing chassis, 911 or 930. We can modify your existing box for about $1500 or sell you a complete unit for $3500. Add about $750 for limited slip or $2500 for a quaiffe. One short note here about the g-50-50 which is the box installed into 1989 and later turbos: they have different (higher) gear ratios and are harder to find thus they cost a lot more.
The next issue to deal with is the fact that you have to convert your clutch and actuating parts to hydraulics. It is simply amazing that porsche used a cable until 1987. We sell a complete conversion as a kit. This will save you a pile of money and time. The kit is around $600 for the parts. Our shop will install all the parts for about $500.
The gear shift lever and mechanism can be had for about $400 and installed at the same time as the clutch modification at no extra charge.
Speaking of clutches, you will need a new set up depending on your horsepower output. A good set up for up to 350 hp will cost $1500. This includes the flywheel and all the necassary hardware. You can upgrade to lighter and stronger parts. Depending on your preference, this will cost between $1,000 – 2,000.
The trans swap also requires new trans mounts$125, longer engine to trans studs $40, special pilot bearing $95, and throttle linkage modifications $45. Also, the g-50 is lower and the rear sway bar you are using, whether stock or not, will not work. We sell bars with drop centers for about $150.
So depending on options, you can figure out the total cost from the above text. We will sell you the above with instructions and plenty of technical support should you decide to take this project on yourself. Of course, our shop is willing and able to provide the labor.
We will also consider your old parts for trade in. The entire conversion using the short box and parts above cost about $1500 in labor. Each car is different, axle condition and other needs will affect the final price. We will be happy to discuss individual needs and offer quotes.