[Trak Ratt]

Chris did you brake your 915 and are now looking for a cheaper replacement?
There is actually (3 or maybe more) trans in this group. The 901, 911 and 915 are peaty interchangeable as far as size and gear sets. Internal parts are different. Later 915s had higher final drive ratios so would also have a theoretically higher top speed. I believe the 901s have smaller clutches than either the 911 or 915. So if you retro with the 901 you would need to make sure the fly wheel and clutch matched the case. The 915 is “rated” for higher torque but the 901 and 911s worked with stock Porsche HP to 180+. The 5 speed 901/911 are also known to have a “weak” 1st gear. The real wild card is the 911 trans. Based on the 901, but with a completely different clutch setup including cable. There are plenty of 901s (teenr’s use a variant) around with big HP motors. The secrete seems to be; easy off the line, no power shifting, narrowish tyres