details, details: notation on COA unverifiable so far

I have a '68 911, Normal, soft-window targa, and trans type 901/74, s/n 9284103. On refurb, internals were noted:
Nurburgring gear set, LSD and 904 main shaft.

But the 901/74 notation from the COA doesn't correspond to anything in current documentation.
Can anybody shed some light here? Grateful for any guidance.

Existing thread from 2014 is linked here:
http://www.early911sregistry.org/for...g-to-find-info

Had an interesting email exchange with Richard Casto at Blue Sky, but netted nothing definitive:
http://www.blueskymotorsports.com/in...id=17&Itemid=6

As can be seen by the thread linked to this post the 1968 sondergetribe numbers and specifications seem to be an ongoing source of mystery due to the low numbers made of each of the available variants as well as lack of "mainstream" documentation. This is despite the fact that they seem to have been special order options across all models in 1968, at least according to the technical spec book.

I dont pretend to have all of the answers and respect the views and information from people like Gordon and Jon (Gled49 and Jon B) as they have had hands on experience with these as well as David's (Davep) database sourced information.

However over the years (with help from those named above among others) I have pieced together some data that may add some light into this murky corner.

I think that there were 12 variants of the 1968 sondergetribes based on 6 sets of ratio options and two different types of material they were made of although I have never seen any examples of some of those combinations. Also as in all (maybe most) things German and Porsche it is possible to identify them by the numbering system used. The little "Technical Specifications" book and other sources seem only to show 5 of these (perhaps for space reasons or perhaps that there were only a handful of each of the other 5 types made).

To decipher the gearbox number mentioned the first three numbers are:
9 for sondergetribe or as stated in the spec book Non standard transmission for 4 or 6 cylinder engines
2 in 1968 was for 5 speed box
8 was for 1968 Model Year transmission (although some were used in 1969 MY 911GTS's )

the next number (4 in your case) identifies the specification of ratios in the gearbox and the same number is used as the last number of the gearbox type number
0 is for a standard transmission or special option
1 is for Hill climb
2 is for airport rations
3 is for fast circuits and
4 is Nurburgring ratios like yours is
and as well as those there was 9 that was "ratio to order"

the next number is intriguing and where i THINK I know what the difference is but am not certain.
there is either a 0 or a 1 in this spot
what is clear is that 0 numbered cases are all 901/5x type boxes and 1 numbered cases are all 901/7x cases

so your 928 41 03 absolutely matches with a 901/ 74 type number and would be the third or fourth in the series (I dont know if the series starts at 00 or 01)

I think that the 0 is for (sand cast) aluminum construction and this is also for the 901/5x types and the 1 is for (pressure cast) magnesium construction aligned to the 901/7x series.

So I am very interested to know if yours is pressure cast magnesium or not.

The final two numbers are the series number for each type implying that less than 100 would be made of any one type although apart from the 91/54 series where I have series numbers up to 35 and the 901/52's and 928 9 ones (which dont have a type number) where they are up to 20, all the rest are only in single digit numbers

So, in summary, this is what I think the available options were and what they are with the examples I have recorded with 928 prefixes linked to a car in brackets:

901/50 92800xx AL standard transmission or special option (0)
901/51 92810xx AL Hill Climb (3)
901/52 92820xx AL Airport (9)
901/53 92830xx AL Fast circuits (0)
901/54 92840xx AL Nurburgring (19)
no type 92890xx AL ratios to order (2)

901/70 92801xx MG standard transmission or special option (0)
901/71 92811xx MG Hill climb (2)
901/72 92821xx MG Airport (2)
901/73 92831xx MG Fast circuits (0)
901/74 92841xx MG Nurburgring (6 but know of 2 other cars fitted with them but dont have numbers)
no type 92891xx MG ratios to order (0)

Davep may have some others in his database

I agree with much of what Hugh says. However I think that all of the 1968 transmissions were aluminum cased. The magnesium transition was in 1969.
So we have 4 series of 5 types with what I think may be the differences:
901/50-54 1968 Al case, 904 mainshaft, regular diff
901/70-74 1968 Al case, 904 mainshaft, LS diff (my guess)
901/75-79 1969 Al case, 904 mainshaft, simplified diff
901/80-84 1969 Mg case, 904 mainshaft, simplified diff
Note that the 904 limited slip would fit in the Al case, but not in the Mg case, so a new & larger LSD was required; as I recall, this was delayed.
There was a series of 901/52 in 1967 with a special serial range.
There were 901/54 in 1967 interspersed in the 902/1 serial range.
Grady Clay was the expert in this field, but sadly passed a few years ago.

It would be great to document this transmission more; with photos of the serial and the main case casting # 901.301.101.0R or 901.301.101.2R
I could help with the Kardex which might have more information. I'd love to get a scan of the COA if possible. This needs more research.
Dave

Dave
I deliberately did not go into the other years numbers because I thought that would confuse something that is already confusing enough - but you are correct that those special gearboxes did exist with similar or identical type numbers in 67 and 69.
On the difference being LSD I dont think that it can be correct - all 911R's had /5x boxes and I would have thought that most of those had a LSD although the kardexes I have on 911R's have absolutely no detail
on the other hand the /7x were on the 69 GTS's and T/R's and L's

here is a partial kardex of a car with a /52 box but definitely LSD (Tiovonen's Monte Carlo T/R rally car) Although It MAY be argued that that is on the kardex because a LSD did not come as standard in that gearbox??


i do agree with Dave that it would be great to document this more and also great to know what your one was made out of

Attachment 466265

and here is a /72 car (Herb Westin's trans am L ) also with a lsd on the kardex

Attachment 466266

Hugh, I do lean towards listed options not being part of standard equipment. So, if a transmission came with LSD as std equipment for the type, then it should not be listed as an option. That is, you only pay for the listed option once. I cannot think of another possible difference between the 5x series and the 70-74 series. I've no idea why this is not "common" knowledge 50 year after the fact. Somewhere all of this would have been documented at the time to guide assembly workers or guide the sales department.

I think those options were all listed in the “Sports Purpose” folder, 25 pages.
(Currently dont have access to my original and cant find scan).

But none are listed in the standard accessory option folders, of which I have all.

This one is 1970 edition
Attachment 466304


And here a bunch of very technical infos, regarding the various gear and transmission choices.
Source: Homologation group 3 - Porsche 911(T) - issued 1967 for 1968 Model Year onwards.

Attachment 466313

Attachment 466314

Attachment 466315

Attachment 466316

Karim, I agree that the options are described in the documents, but they do not link the type #'s or serial #'s to the options. Nor do they seem to link mainshaft and differential. So the documents do not really help to advance our knowledge very much.

Thx Dave..its technicially too complicated for me:p . I recall “Sports Purpose” had much more infos, ill try to get a scan.

Karim. I have looked in sports purpose before. It has suggestions for different transmission ratios and gives the specifications of different gear sets that are available, gives part numbers for the different pinion and gear sets but nothing to indicate type numbers or what case differences there may be
Dave
if you note the kardexes both /5x and /7x gearboxes shown above have lsd on kardex so i am convinced that that is not the answer. I think the case number of the OP’s gearbox or other identification of what it is constructed of may help here

Here are 4 gearboxes I know about: a 67, 901/53 LSD w/Nadella drive flange, #103xxx. 68 R 901/51 LSD w/Nadella, 9281xxx. 68 R 901/54 LSD w/Nadella, 9284xxx. 68 R 901/54 LSD w/Nadella, 9284xxx. All had 904 m/s, some had original gears, some had modified ratios. 2 of the R boxes had 906 pinion shafts w/ castle nuts instead of streatch bolt. All ALU cases. The R's Kardex don't list LSD's separate. Gordon

kardex has been ordered

case is aluminum

here's the COA
Attachment 466355

really appreciate all the info and feedback.