915/61 vs. 915/63

[wtmeyer]

Can someone tell me what the difference is between /61 and /63 915 transmissions? These were used on the 911 SC. 78-79 for the /61 and 80-83 for the /63. Is it different gear ratios, R&P or trans case?

[maxnine11]

from the shop manual:

the 78/79 uses 915/ 61
the 80/81 uses 915/ 63
the /63 differs from those in the 1978-79 models only in the modified 2nd gear ratio.

915/ 61 2nd gear = 18:33 = 1.833

915/ 63 2nd gear= 18: 32 = 1.778

max

[wtmeyer]

Thanks, Max. That was just the information I was looking for.