901 & 902 transmission

[porschedreamer]

hello porsche gurus,

whats the difference between the 901 & 902 transmission? is there a 902 transmission or is actually the 901 transmission but designated as 902 because its put in a 912

[AirJose]

Come On! Is a good question. Please someone let us know.

[tonykof]

ttt

[914Ghost]

I'm not sure about this- but I'll take a guess.
The 901 was 4 or 5 speed depending on options and the 902 I think was only available as a 5 speed unit.
Also, the 901 was the tranny used in 914's, 902 only came in 912's?
Someone should know. One is as good as the other as far as I know.
I also would like the facts.
Bob O

[Sweetheart912]

OK, here is my stab at it. Other than the name (901/902), the most singular difference in 901/2 transmissions are ratios (see charts below). Over the last 40 years, Porsche used 9xx design sequence numbers to describe their cars. In 1963, Porsche called the new six cylinder model coupe a 911, but retained 901 for the model designation. Porsche called the four cylinder coupe a 912, but retained 902 for the model designation. The model designations were primarily for part identification categories, including transmissions.

The most significant difference in early gearboxes (prior to 72) & later models, I could find, was that in 911 and 912 5-speed transmissions (type 901, 902) second gear was integral with the main (input) shaft. This necessitated changing this shaft to the 904 type shaft before the second gear ratio could be changed. This was changed after 72 in the type 915 so that first gear is integral with the main shaft, thus making second thru fifth ratios easily changed. There were also minor external changes between early & late boxes, and 901/902's; but were mostly differences in mounts (interchangeable) & types of bearings & seals. Early 901/02's used Nadella half shafts & later 901/02/15's etc used Llobro half shafts.

Note 911 & 912 shared some common gear boxes (901 & 902). You will see the gear ratios & ring & pinions listed. The 902/06 was the most desirable and was sought out by SCCA racers for many years to get the 6:29 R+P that coupled with a few gear changes on a 904 type shaft, particularly a W gear for 4th, & you had a real respectable race gearbox.

This list is the recurring sets of the standard gear boxes in factory books. There were also some “special transmissions” with 901 designations during this time period, but they were strictly racing versions or European performance versions for 911's (Autobahn Polizei). They were not offered to the public and it is pretty remote one of these would be in any of our street cars.

Rather than a commentary, each of you can look at it and draw your conclusions about what is in your car. I listed the 911 boxes thru 74 for further comparison.



912............................................... .................................................. ....912
1965-69* 902/1 11:34 18:34 22:29 25:26 28:24 7:31
(5-Speed) 902/02 A F M S X
902/05
1965-69 902/0 11:34 19:32 24:27 28:24 - 7:31
(4-Speed) 902/01 A H Q X
902/04

912............................................... .................................................. ....912
*Late 69 902/06 11:34 18:32 23:28 26:25 29:23 6:29
(5-Speed) A GA O U Z

912E.............................................. .................................................. 912E
1976 (5-Spd) 11:35 11:33 23:29 26:25 29:21 7:31

911............................................... .................................................. ....911
Up to 901/0 12:34 18:32 23:28 26:25 28:23 7:31
7/26/65 AA GA O U Y
(5-Speed)
1966-69 902/1 11:34 18:34 22:29 25:26 28:24 7:31
(5-Speed) 901/02 A F M S X
901/07 or 29:23
Z
1966-68 902/0 11:34 19:32 24:27 28:24 - 7:31
(4-Speed) A H Q X
1969-71 901/06 11:34 19:31 25:26 29:23 - 7:31
(4-Speed) 911/00 A HB S Z
or 29:22
ZA
1970-71 911/01 11:34 18:32 23:28 27:25 29:22 7:31
(5-Speed) A GA O V ZA
1968-69 905/00 15:36 19:31 23:28 26:25 - 7:31
(Sporto- 905/01 C HB O U
matic) or 27:25
V
1970-73 905/20 15:36 20:31 24:27 28:24 - 7:31
(Sporto- 925/00 C I Q X
matic) 925/01

1972-73 915 11:35 18:33 23:29 26:25 29:22 7:31
(5-Speed)
Trans
73 915 11:35 18:32 24:27 28:23 - 7:31
(4-Speed)
1974 915/06 11:35 18:33 23:29 27:25 29:21 7:31
(5-Speed)
1974 915/16 11:35 20:32 25:26 29:21 7:31
(4-Speed)
1974 925/02 15:36 20:31 24:27 28:23 - 7:27

This list & my observations may not be all inclusive to the last little detail, but hope this helps with the mystery. Cheers.

[porschedreamer]

I bow to you! - HAIL Sweetheart912

[Sweetheart912]

Thanks. Some additional trivia I found on the sequence numbers. When Dr Porsche started his company in the 20's, he simply numbered each design project he had with a number, beginning the sequence with 001. Every job was then sequentially numbered to include the Panzer tank design, the KdF wagen & many others. The 356 was actually design project typ 356 & as such became the "name" of the car. Replacement parts were designed & tracked by project design numbers. I reckon this is good Teutonic logic. The exception was the 911. It was actually design project 901 but Porsche was sued & tied up in the courts by Peugeot. It seems the French claimed world rights or some foolishness to the number 901 for automobiles. Naturally, the time was still considered post war & the French won the case & Porsche was forbidden to use 901 as a car name. Butzi Porsche transferred the 901 work to the newest project design number available which was 911 for naming purposes, logically followed by 912. The parts though were kept in the original design project sequence. My guess is because they already had the parts lists worked out & in pre-computer days, that was a LOT of onion skin paper & white out work. The rest is history. I think design project 913 was a truck, then came the 914. Production didnt always match design though...for example 904's & 906's were designed & put on race tracks before the design sequence number 901 (911) made it to production. Over the last 40 years, Porsche used most of the 9xx design numbers to describe their cars, though one or two recent models are better known by name rather than their 9xx code, for example the Boxster (986) and the Cayenne (955). Thought you might be interested.
Cheers.

[ettsn]

Good info, although let me add a few things:

Peugeot owned the copyright to all three-digit vehicle models numbers with the central digit being a zero. That copyright elapsed, and thus allowed for cars like Ferrari's 308, for example.

The Cayenne is not 955. It's 9PA. The 955 in most of it's part numbers designates that part is not built by Porsche (or sourced through normal Porsche channels). All the VAG (VW) sourced parts in the Cayenne carry the number 955.

-Paul

[bluehawaii]

does the 912 , 911 1965 thru 1969 interchange?

[bluehawaii]

Are the transmissions the same( 911 ....912) year 65 thru 69?

[djpateman]

There were a lot of type 901 & type 902 transmissions. Some were 4 speed, and some were 5 speed. The early ones were aluminum case, and later ones were magnesium case. There were several types of output flanges, notably the Nadella and the Loebro types, and there were a few sizes of the latter. I think the 912 only used the type 902 series, but I know the 911 used both type 901 & 902. There were quite a few combinations of gear ratios available in the different types. To answer bluehawaii, no, not always.

[bluehawaii]

ok ...thanks,,
I have a 66 912 with a 4 speed...it has the # 902/0 stamped on it...I think it is original. Anyways my 2nd gear grinds unless I shift it perfect. I think the @nd gear synchro might need replaced. Wondering if I should get another tranny until I can rebuild this one or just get this one rebuilt. I am on a budget and live in Hawaii....(outer island).so it is a little challenging.

[Jaems]

The 902/0 was for the US and was a four speed in 66 for the 912.
The 901/** was for the original 911 in 65. The later 65 911's used the 902 series. The basic 911 used the 902** until the 68 Model year. The 67 911S was the only model to use the 901/ case until 68.

In 67 the factory changed from the Nadella to the Löbro type flanges. The early Löbro flanges can be installed on the early 902/901 transaxels to take the early CV's. The 69 because of the longer wheel base and different bolt pattern. will not work or the CV's on the earlier cars..

[WFBowen]

I'll post these charts again for those who might be searching....

[cseely]

Just wanted to know if a za 29:22 will fit for the 5th gear on a 1966 912. just need a better final gear and lower rpm. thanks for any help. it will replace the 28:24.

carl seely

[Matt Monson]

yes, all 901 gears are cross compatible.

[Brett Voigt]

I am doing a Jake Raby kit rebuild for my 69' 912. Hopefully should get a bit more HP and torque out of it. Just curious if anyone knows how much power the stock transmission can withstand before it needs to be upgraded?

[keitho64]

Brett

I have a 1969 901 gearbox behind a 2.7 6 from a 1977 911S. The 2.7 is running webers, early headers and mild cams. I am not sure of the HP but I imagine it to be north of 175-180HP. Someday I will put it on a dyno. The car has been like this for a few years without any problems on the 901. I never do hard starts with the car but I am not a lazy driver.

The 901 has been flawless for me. Unless you are building some wild horsepower / torque monster for drag racing I would expect it to hold a strong 912 motor.

[WFBowen]

Ditto what Keith said - the early 911 racers used the 901 gearboxes with some pretty powerful engines. And, don't forget that the 914-8 guys (basically the same gearbox) have used the 901 with mild to wild small-block Chevrolet motors for years, although the few I have spoken with don't push things too hard off the line in 1st.
Bill

[Jaems]

The original shaft of the 901/902 was a little too small and a few failed with the end broken. The factory came out with a beefed up version as a replacement. They were only replaced if yours failed. Some of the 901/902 still have the smaller weaker shafts.

The 901/902 part numbers, as stated were never changed from the original designations. The lawsuit was for the car designed numbers not the parts.

The 912 was originally designated as the Type 902. All parts that pertained only to the 912 will have the 902 prefix to the part numbers. Otherwise they will use the 901 part numbers. The 911's will use only 901 prefixes for parts.

So the 902 transaxle will have shorter top end gearing than the 901 transaxles, do to less HP and Torque than the 911. However, any of the gearing ratios are inter changeable between the 901/902 with the exception that the 4 speeds have to remain 4 speeds.