[Grady Clay]

Bobby is right on.

This is one of the few simple issues that Porsche did that doesn’t pass the engineering laugh test. No offence intended as they did so much else well.

Porsche had historically put the transmission serial number and type numbers stamped in the rib just behind and below the differential area. This was reasonably well protected from pavement abuse. I think this was true from the pre-war VW era.

For the ’71 model (and it may be true from late ’70 models, but just pre-July ’71), the later version of the Type 911/01 and variants had a nice boss cast under the differential area for the serial number and type number. This was very well protected from road abuse. This was the last use of the type 901/911 but continued through ’76 with the different) 914. Some ’71 914-6s had the later 911 casting.

Starting with the ’72 915, Porsche forgot everything they learned and put the transmission number, transmission type and LSD designation on the clutch cable support under the differential. This is the LOWEST point on the transmission and 99% of the numbers have been ‘scraped off’ by contact with the pavement. It was such a poor design that the clutch cable support broke off, fixed with a separate part.

No one is laughing now because it is very difficult to determine the actual type number of a 915 without dissemble and impossible to recover the transmission number without very expensive forensic attempts.

The good news is you can tell all the important ‘facts’ only with simple inspection and disassembly of the transmission. Nothing you wouldn’t do in a normal service and repair.

If anyone is concerned about their transmission sequential number (7TypeYearxxxx), LSD indicator number (12) and transmission type number (915/xx), get your CoA from PCNA and make it correct.

Same issues with a 930.

Your local State Police might be convinced to apply their forensic magic. Our ever diligent FBI is too buisy chasing phantom spooks to bother with lowly Porsches (told this first-hand several times recently).

Best,
Grady