Is there some data out there on the 901 tranny differences between the years it was manuafactured?

Do all 901's have the same shift pattern?

They all have the same pattern.

6's have different gearing. I'm sure various years do as well. I don't have any info handy on that. 70-72.5 were tail shifters (check that final year) the rest were side shifters. Tranny remained the same but linkage changed.

911's had two versions (basicially... someone's going to get in here and flame away about 901/01's and 02's and so forth but...) The 901 which had the pull clutch mechanism (1966-1969) and the 911 which had the push mechanism (1970 and 1971) in 72 they switched to 915's

That's all I know and it's probably suspect at that

'73-'76 had the side-shift linkage (different shifter bits inside the case, and a different tail cover). '70-'72 had the tail-shift linkage. The 914/6 models had different gearing, and all of them were tailshifters. The shift pattern (dog-leg first) is the same for all of them.

Note that "901" is also used to designate the early 911 transaxles, which have yet another external linkage, and another tail (well, nose on the 911) cover. Gearing was probably different, too. This also used the dog-log first shift pattern. The 915 was the first gearbox in the line to use the "first forward" shift pattern.

I am doing a /6 conversion on my 1970 1.7L. Right now, I have been planning on a 3.2L conversion, but am concerned about the 901's ability to handle the horsepower (I still want to be able to use 1st gear). I am starting to lean towards the 3.0L CIS motor with 180HP.

It sounds like thos who have converted /4's to a /6 (2.0, 2.2, 2.7, 3.0, 3.2L) have had to change the gears anyway on the 901?

You don't really have to change the gears, you just don't use first and drive it like it's a four-speed. First is the weakest (forward) gear in the 'box, as it's only supported at one end. With the torque provided by most Sixes (at least the 2.4s and up), first is unnecessary, anyway. You can spin the tires in second with a 2.4. With a 3.2, I'd bet you could start up a steep hill in third w/o slipping the clutch.

The V8 guys often put in taller gearing simply because the V8 makes so much torque at such low revs, there's little reason to spin it as high as the stock gearing will do.

The 2.0 Sixes only had slightly different gearing, and I believe it was actually even shorter than the /4 gearing. That engine really likes to rev.

A table of the available gear ratios:
http://members.rennlist.com/chuxter/901&915ratios.htm

Some 901 boxes from 911s and 912s were four-speeds. Not many, though. And of course there were the "Sportomatic" transmissions, which were either three-speed or four-speed, I forget which. But those are a very different animal indeed.

From my readings, I think 3.2 is where you run into enough problems with the 901 to make a 915 conversion a better idea. The 3.0 engines seem to do OK with 901s that are in good shape, but from the sound of it the ones hooked up to 3.2 motors start having real problems...

--DD

I guess my decision will continue to "weigh" in my head. Although not everyone likes it, I really want to keep the that cool, funky shift pattern.

Maybe I will have to kick around the idea of a 2.0 or 2.2L with carbs or get hold of Mr. Raby for a big four. Monster horsepower is not my goal for this car (1970 1.7L). Heck, maybe I'll just go with a 1.9L rebuild of the motor.

I really feel like I would like my 914 rebuilt 914 to have around 160HP (180HP seems max with the 901...it was for Porsche). 140HP would be the low number for me.

Decisions, decisions...

No reason you can't keep the stock gearbox with a 3.0. Just don't expect to make hard launches with any regularity. It's the shock loading from popping the clutch and making rapid shifts that kills gearboxes until you get into really silly torque figures. In higher gears, you're not creating such high loads, and with the torque of a 3.0, you can use fourth where you'd need to use third or even second with the 1.7.

.........

I have a 2.2 liter 6 conversion and would like to change out some of the gears.
Does anyone know if the gears from a 911 trans fit into one from a 914, both being the 901?

Thanks, Craig

Gears from all 901 transmissions are the same (except for the number of teeth, of course !). You can take gears from any 4 or 5 speed 911 or 912 trtanny and they will fit. Actually, there are things you can't do, a third gear might not fit in the fourth gear location for example. Not sure this specific example is correct, but something to be careful about. On a four gear tranny, it 's the "first gear" that's missing. If you look at the shift pattern, it'l be obvious.

Second gear can't be easily changed, because it's part of the mainshaft. You either get a complete different mainshaft (probably 2 or 3 ratios over the years were put in second gear) or you get a 904 mainshaft, which is rare and expensive.

All 914 trannys had the same ratios. On 911s, they varied from displacement to displacement and model to model "T" , "E" and "S", plus custom racing stuff.

There's a lot of ratios available.

I have a 2.2 E engine, with a redline north of 7K. That means 90 mph in third gear. I currently have project on the backburner to shorten 3rd 4th and 5th gear.

HTH

Michel Richard

It all depends upon you......

How are you going to drive the car?

Our 901 lasted several (6 or7) years doing only track events with it until we started pushing the car hard enough to start destroying 901 boxes. We are usually gentle with them, but for some reason, when pushed very hard we ended up always breaking the teeth off of 4th gear. (never had a problem with 1st)

First will be a granny gear and useful only for getting the car rolling.

Yes you could start off in third and not slip the clutch much (up a hill even)...

We converted to a 915 box and haven't had a single problem (knock on wood)....

It just boils down to how YOU are going to use the car. 901s can last a long time if not pushed to the limits constantly.

We never changed ratios in any of the 901 boxes we used. It got to the point of destroying 1 or two a year until swapping it out with a 915 box....

Just my $.02

From 97 til 2001 I had a 3.6 l in a 914 with a side shifter.beat the hell out of it autocrossing and a few DE's not one problem !!! they handle up to 270 hp with out a problem as long as it is in good shape when you start. As far as I know the car is still runing fine up in Mass,only thing I heard went wrong with the car is that they painted it pale yellow!!!