1975 915 Trans R&P ratio

Jim Schrager · 12-27-2008, 07:53 AM

Does anyone have the 1975 Porsche Spec book handy?
I need to know if the R&P for a 1975 is 7:31, as it is
in 1974, or 8:31 as it is in 1976. This data will
appear on the Trans Spec page of the small format
Porsche published Spec Books.
Many thanks, Jim Schrager
Sports Car Market magazine
jimschrager@compuserve.com

BURN-BROS · 12-27-2008, 09:31 AM

1975 should be the 1st year of the 8:31 rp.

from rennsport system's site;

"The 915 appeared in 1972 with a major upgrade in strength, compared to its predessor. The first ones didn't shift as well as the later ones due to some improvements in the shifter and syncro's. 915's were made with magnesium cases from 72 until 77. Some of them had aluminum final-drive cases in 77 before the entire gearcase was made from aluminum in 1978. 915's used 7:31 ring & pinions until 1975 when they switched to the stronger 8:31. These later ring & pinions are the preferred item for racing or high-horsepower applications and the later 915's had stronger differentials and mainshafts. "

Steve@Rennsport · 12-27-2008, 12:21 PM

Hey Jim,

Aaron is right,...

BURN-BROS · 12-27-2008, 01:05 PM

Quote:

Originally Posted by Steve@Rennsport

Hey Jim,

Aaron is right,...

LOL...actually you are right. Merry Christmas!

Henry Schmidt · Henry Schmidt's Garage

Aaron and Steve are correct with one caveat: Porsche had/has a special division that allowed a customer to order any number of custom parts. R&P was one of those special order options.

Jim Schrager · 12-28-2008, 06:56 PM

Many thanks for the responses, it looks like 1974 is the last year of the 7:31 R&P.
I appreciate those who took the time to send a post.
Best regards, Jim Schrager