OK Gents heres the ? what the diiferance between 901- 914 -915 I seen a tranny yesterday that had the # 914.XXX.XXX I thought they were all 901 and 915

901 is for a 911
914 is a 901 set up for a 914 (flipped R&P and sideshift)
915 is for a 911

Here's a brief rundown of production (AKA, "street") transaxles:

901 (and 902): 1964-1968 911/912, chill cast aluminum case. 1969 911/912, mag alloy case with larger differential. Both 4 and 5 speed versions. First production Porsche transaxle with jointed axles instead of swing axles. 2nd gear fixed on mainshaft.

904: 901 chill cast case, 2nd gear not fixed on the input shaft, ring gear flipped for mid engine use. 5 speed. (Yes, there was a "street" equipped 904 available on order.)

905: 1968-1971 Sportomatic version of the 901, 4 speed

911: 1970 & 1971 911, mag case, pull type clutch. Both 4 and 5 speed versions.
Known to be weak in the area above the front bearing races. 2nd gear fixed on mainshaft.

914: 1970-1976 914, mag case, ring gear on opposite side from others for mid engine use. 5 speed only, gear ratio differences for the 914/6. 2nd gear fixed on mainshaft. Versions to 1972 were "tail shift", 1973-1976 were "side shift", a simpler system with fewer components, and less prone to wear.

915: 1972-1977 911, mag case, several minor variations. Both 4 and 5 speed versions. 1978 and up, aluminum case, internal improvements as time went on.
Final drive ratios varied in production. Later versions had electric speedometer drive components. The 911 Turbo used a reinforced 4 speed version of this transaxle. Factory oil cooling was available.

916: 915 transmission, modified and fitted for mid-engine use in the limited production 916.

923: 1976 912E version of the 915.

925: 1972-1983 Sportomatic version of the 915, 4 speed.

There were various racing versions of all the manual transmissions.

The Cap'n

We often call our transmissions "901" gearboxes because the 914 transmission is based very closely on the 901 version. That's where a lot of the confusion comes from...

--DD

What's the designation of the 911 trannys after 77?

so a side shift #914.xxx.xxx tranny would be ok in 1970 914-6 ..would it make it better ? or should i just leave it alone..the one in the car is a tail shift...Thanks for all your help

"915"

The Cap'n

the shifting would probably improve a bit with a /4 sideshifter, but the gearing would be off.

plus, if you replace all the shift bushings on a tailshifter, they can be made to work quite nicely ...
Andy

The 914/6 had a different tail shifter setup than the 914/4. Because of gearing differences, it would be better to convert the 914/6 tranny to a side shifter than to use the 914/4 side shifter tranny as a replacement unit.

The Cap'n

Thanks to all GREAT INFO...MAN I LOVE THIS PLACE

andy, so how many 914/4 side shift gear variations are outhere? seems like the stock gears ratio's would more or less be fairly common/similiar, except maybe with a package option... where there optional ring gear sets?

mike

1

but he was talking about putting a /4 sideshift in a factory /6 car. the factory /6 tailshifter tranny has different gears than either of the two /4 version ...

Andy

Yep... what andy said
no stock -4 gearing options were offered.

but anything is possible as a modification
brant

opps... my bad, i see now you where origanally refering to the 6/(915?)... but you answered my question. all 4's (901's) had the same gearing, right

mike

STOP! Read my earlier post! The /6 DID NOT HAVE THE 915! It had a tail shifter 914 (901 derivative), but the shift mechanism was different from the /4 tail shift components. All the /4s (914, a 901 derivative) had the same gearing.

The Cap'n

Yikes. Kind of confusing.

The 901 is the box part, the 914 part number is seen on the end cover...this is the part that enables us to put it into the 914.

The stock /6 is a unique tail shift set up, but since it is based on the 901 box, it can easily be converted to side shift using the side shift goodies from the stock /4

The gears in the /4 boxes are all the same stock.

The gears in the /6 boxes are different from the /4 gears as /6 gets tq and likes rpm at different spots than a /4.

Clearer? I can take pics if ya'll still need. I have the parts from all mentioned.

I thought the 914.xxxxxxxx part #'s only came on the sixes????

Nope, look at your tail cone on your tranny, it will start with 914.

I think you're thinking of the VINs.

Is there a part number on the case? I could swear I read somewhere that the sixes had a different part number. The VIN's are definately different.

You are right, Ted. The /6 cases, although identical to the other 901 cases, have a part # that stars with 914 rather than 901. Sorry for the confusion on that one.