there have been a few threads on decoding gearbox numbers. Most have been on the early ones; not the 915 ones.
However this is what I think i have gleaned from books, threads etc on the codes for 915 boxes.
There are 7 serial numbers describing the gearbox not including the type number.
the first three all mean something and the last 4 are the consecutive serial ones for that type and year.
so take 7 1 3 1234
7 is the code for a 6 cylinder car - ie 911
the second number is the gearbox type - see below
the third number is the year 3 for 1973, or say 9 for 1979
and the last 4 (1234 in this case) are the consecutive serial numbers of that type
My query, after taking a photo of my number which makes it much easier to read than i have been able to do in the past is about the second number.
My records show the following as decoding the second number:
0 four speed standard ratio
1 five speed standard ratio
2 four speed sporto
3 five speed optional ratios
4 four speed optional ratios
5 no record
6 no record
7 no record
8 RS five speed with oil pump.
I have always thought that my gearbox number was 713 1350. This is from reading the number on the box as i have never had confirmation from Porsche and it is not in my maintenance and delivery documents unlike the engine number, key number and chassis number.
It is a 73 E build in June 1973 with chassis number 1306- ie almost at the end of the run of 1366: and in fact just over 95% of all coupes by number were built before mine if using the production number as a guide. It has had standard 5 speed ratios in it as long as i have had it (nearly 20 years)
The production number (ie for 73 coupes of any sort built) is 89xx ie over 8900 coupes of the 9447 built that year.
Obviously a fair number were sportos and a lot were 4 speeds , probably 1500 by then were RS's with an "8" gearbox and there were a number of optional ratio gearboxes. However IF my number is 1350, and is a standard box, and it is original to the car which is what i understand, going from my production number if they were assembled in rough order and targas were built at about the same rate as coupes, it would mean that less than 10% (maybe about 9%) had "713" gearboxes - ie standard 5 speed boxes.
This seems to be in complete contrast to Australian deliveries for 1973 model year cars. Excluding RS and RSR's 91 cars were delivered here. of those 91 almost 50% (44) were 5 speeds, 40 were sportos and only 7 were 4 speeds. That has a lot to do with how cars were spec'd for Australia but it is a huge divergence.
what has be thinking is this photo i took of the number today. The number is badly scraped, as many are due to where they are placed and the type number (which would help here) is completely missing. However the numbers in the photo have made me question all that i have believed about this in the past.
Knowing the first number is a 7 and having a 1 in the series, even though a lot is scraped off, to me the second number looks much more like a 7 than a 1. I think it SHOULD be a 1 but i am wondering if i am correct or maybe IF the numbers i don't have a record for (5, 6 and 7) were actually used in some gearboxes?? in addition the apparent low number of 5 speed standard boxes (assuming they are used in roughly the correct order) also puzzles me. I am going to check my databse of Australian cars (where i have gearbox numbers) to see if mine is out of sync with them or not.
anyone have any thoughts?
Reply With Quote
Originally Posted by drmrfi
