1983 Porsche 911 SC Targa

Wednesday, April 25, 2012

Transmission Maintenance

There are four transmission seals that I replaced – the input drive shaft, two output drive shafts, and the gear selector shaft. The seals must prevent gear oil from leaking out and allow the shafts to rotate freely. I also changed the gear oil. The throw out bearing fork came in my clutch replacement kit.
Old worn out parts that were replaced - clutch spring, oil seals, clutch release fork, and jack port covers.

New clutch release fork installed in the transmission bell housing.  I had to file down some of the casting flash at the top and bottom of the bore to get it to fit.
Because I am keeping the transmission in my EV conversion, I cannot eliminate all of my oil use with this car, but usage is greatly reduced because the oil in the gear box is not changed nearly as frequently as oil in the crank case. There are AC electric motors capable of going without a gear box (direct drive or fixed gear). They are used in most commercial electric vehicles. AC is cost prohibitive to most home hobbyists converting their own cars. The DC electric motor I selected has a wider torque band than the gasoline engine, but not wide enough to eliminate the need for a transmission. I expect to use 2nd gear to accelerate up to 45 MPH (70 km/hr) and 3rd gear at greater speeds. The reverse gear will also be required. In addition to being more economical, the DC motor will have more torque available at low RPM compared to AC electric and gas engines – peak torque is available from 0 to 2500 RPM.

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