Transmission number?

[BK911]

Trying to decipher a tranny number.
Anybody know the difference between a 771xxxx and a 711xxxx?
What does the "7" mean?

From here:

901 Series Porsche Transmission

Shows:

901, 902, 905 and 911 types

AAA/AA BB CDE NNNN

A = Type (i.e. 06 = 901/06)

B = Differential Designation, 12 = ZF LSD, missing = no LSD

C = Application, 5 = 4 cylinder engine, 7 = 6 cylinder engine

D = ?

E = ?

N = Sequential Serial Number (i.e. 0001, 0002, etc.). Some models did not start with serial number "1"

Thanks!

[Peter Zimmermann]

711xxxx
7 = trans for 6 cyl engine
1 = 5 speed std ratios
1 = 1971
xxxx = consecutive build number


771xxxx
7 = trans for 6 cyl engine
7 = not a choice per my references
1 = 1971
xxxx = consecutive build number

[djpateman]

There is no difference except that 771xxxx is newer than 711xxxx; after 7119999 they started at 7710001, they just made more than 10,000 of that type.

[Peter Zimmermann]

pate; what did the factory do, when changing to the "7", regarding type, i.e., 5-speed, 4-speed, Sporto, etc.?

[djpateman]

Peter, I don't really understand your question.
This is the type 911/01 with A-GA-O-V-ZA gears, and applies to both 1970 & 1971.
If you build more than 11,000 transmissions of one type in a year and you have only 4 digits for serial #, then you need a second series; so 710xxxx becomes 770xxxx and 711xxxx becomes 771xxxx. The 770 and 771 series just appear late in the model year. No physical changes.
Dave

[Peter Zimmermann]

Hi, Dave. Sorry for the confusion. I found the more complete list in the Spec Book (page 62), and it appears that Porsche abandoned the 2nd digit info code per the 7"1"1xxxx number, and used a "7" in the 2nd digit to cover all the late transmissions. Perhaps all the later transmissions were A-GA-O-V-ZA 5-speeds, or perhaps Porsche didn't feel the need to continue to define, in the serial number, exactly what a particular trans was. Or perhaps they saved enough 711 serial numbers to cover special builds and Sportos. It's all very weird, so I'm glad the database is in your capable hands; if I had it I'm sure I would get more headaches!

[djpateman]

Pete, no problem, and I like trying to get these details straight. Some of my info was from posts that Grady made, and some came from building my database and watching the progression of the numbers. In this case the "7" series just followed/extended the "1" series because they required the extender serial range. This was not unique with the transmissions either. Here is the list of 1970 911T engine numbers:
911/03 6100001 6103000 ROW
911/06 6103001 6103230 ROW Sportomatic
911/03 6103501 6104547 ROW
911/07 6105001 6107999 North America
911/08 6108001 6108374 North America Sportomatic
911/07 6108501 6109955 North America
For both the 911/03 and 911/07 engines they underestimated the ranges they would need when they set the pattern up, and had to add an extended range for both types. They almost ran out of the extended range again for the 911/07. For 1971 they changed the pattern a little so as to avoid needed two serial ranges for one engine type.

[Kiwi John]

Hi This has probably been covered elsewhere, I have a 901 box , 5 speed , but the crown wheel is turned over ( so it is running on the other side of the pinion) giving it 5 Reverse Gears !!! The numbers on the case are #901/ 01 7700 982 ( 1970 2.2 5 speed ? ) But , with 5 reverses ……The case looks mint , no other changes . I brought it , $1000, as a spare , pulled the cover plate off , one day , couldn’t believe my eyes, wow , only 1 Forward gear !! Thanks Kiwi John

[Matt Monson]

Originally Posted by Kiwi John

Hi This has probably been covered elsewhere, I have a 901 box , 5 speed , but the crown wheel is turned over ( so it is running on the other side of the pinion) giving it 5 Reverse Gears !!! The numbers on the case are #901/ 01 7700 982 ( 1970 2.2 5 speed ? ) But , with 5 reverses ……The case looks mint , no other changes . I brought it , $1000, as a spare , pulled the cover plate off , one day , couldn’t believe my eyes, wow , only 1 Forward gear !! Thanks Kiwi John

Someone must have used it in a mid engine racer, like a formula Ver, or similar. It’s totally reversible. You’ll need someone to reset the ring gear backlash and preload, but it’s a straight forward return to stock.

[Kiwi John]

Hi, Matt, thanks for your reply . Yes , that was the answer I came up with . Doesn’t look as if it has had a side shifter on it , at anytime. A handy cheap find, as an extra, if required. Cheers