Hello 986forum! Here's the DIY oriented thread I posted in general discussion. Feel free to discuss the more technical aspect and specifications of the swap in this thread.
Find yourself a donor. I found an audi a4 5speed manual transmission. Quattro will not work. Some VW passats will work too. S model boxsters can utilize a 5 speed transmission - but require a lot of modification, e.g. axle flanges, mounting hardware. There are forum members with 3.4 996 engines and 97-99 5 speeds. The swap I performed is practically a direct bolt up for 97-04 2.5s & 2.7s. It can be done with S models, or 3.4 etc.
Drain oil from old transmission, remove axle flanges- they are not compatible with 2.5/2.7 axles. But- interestingly audi flanges should be the same as S model chasis axles.
Remove Boxster transmission.
With boxster transmission removed, switch out axle flanges and swap all hardware between the transmissions.
Putting the Porsche flange in the Audi transmission.
Re-assemble
note: If you do not have M12x1.5x70mm (999-072-008-09) 'G' bolt location picture, it would be recommended to order and install
http://www.pelicanparts.com/techarticles/Boxster_Tech/37-TRANS-Drop/images_small/Pic4.jpg The boxster transmission has a stud in the case, whereas the audi does not. G bolt did not come with my car.
Total cost: $200
Results: Shorter, more aggressive gearing. First gear takes off like a bat from hell. Highway cruising in 5th is slightly more efficient compared to G86/01 5spd Boxster transmission.
Ratios:
Final Gear Drive 3.889
1st 3.778
2nd 2.176
3rd 1.429
4th 1.029
5th .838
(Similar ratios to G86/00 97-99 boxster, albeit shorter)
RPM Chart: (calculated with 255/40/17 tires)
