901 Tranny: 914 vs 911

Any one know of a real functional difference between the two? I understand that the gearing is different and possible differences in shifting, tail vs side. But, are the internals different? Obviously, the 911 was rated for more hp/torque.

i.e. Would you use the 914 - 901 in your speedy? Buying anything with "911" attached to it costs a bit more and I've seen the 914 trannies selling for less on the web.

If want numbers then... how about with a Type IV with 120-140ish HP/Torque.

Wil

Angela knows these things best and I think she's explored this topic before in one of her posts....

Other than the shifting, reverse pinion gear flipped and gear selection I think a 901 is the same regardless of whether in a 911, 912 or a 914.

Angela??

Agreed. Pretty much the same. Early 914 901's are tail shift which aside from the ring and pinion to flip, makes them an early 911 transmission. No problem with those torque figures. That's going to be pretty easy on the transmission.

angela

Oh, you know what, the mounts at the tail shaft end (to the car) might be different. Internally the same, but the rear case could be different. The side shift is definately different so the rear shift may be also. On the side-shift the transmission "hangs" from a casting at the topside. On a 911, the transmission sits on a cross mount.

angela

Angela,

Are these the differences?...

First 911 then 914 tailshift.

Wait. Is that second picture a tailshift or sideshift? I assume those rear 914 mounts are the ones that 'hang' the tranny.

Wil

Looks like later 74 (or was it late 73) side shifter. Although that was better shifting trans in the mid-engined 914 suspect it is more difficult to adapt the a Speedie. It probably sells for a few more $ too since early 914 owners liked to swap it in. (I had a 1.7L '72 914 - and aside from rust bug, I loved the handling).

The second transmission is a 914 side-shift. Its the big "eared" casting that I'm questioning. I don't know if it is also present on the 914 tail shifters. Hmmm... Wait, I think I know where to check.
angela

I've read several article on 914 owners updating the tail shifter to the side shifter. The mounting of the trans (via the ears) seems to be identical as "all" they need are the shifter,cable and later motor mount pieces to do the conversion. Good article at Pelican -

http://www.pelicanparts.com/techarticles/914_shift_improve/914_shift_improve.htm

Angela...

its a tail shifter..same as on my 72 914. I have a side shifter on my 73 914. They both mount the same.


Michael

You're right, Michael. 914 tail shifter. The last tail shifter 901 we had out was from a 911 - looks different. My bad.

This is a 911's 901 transmission (this is the shifter I was picturing that a 914 had - DOH).

Oh, by the way, there's one of these on the Pelican BBS site for $450 right now.

angela

Angela,

In the photo in your last post, it looks like the tranny has the aftermarket billet intermediate plate. Do you know if this really helps the 901 (other than replacing an old, worn part)? Does this support the shaft any better to help alleviate the problem of the first gear outboard of the bearing, or are you still just stuck with not hammering the throttle in first?

I would think that since these cars are lighter than the 911 the boxes came in, you should still be able to drive aggressively (depending on the torque you're putting behind it), as long as you tame the dump-the-clutch urge.

How does the 901 hold up in your car?

Thanks,

Bob

The 914 guys swear that the billet intermediate plate greatly improves the transmission life span under very hard driving (and yes, you're right that one is equipped with that). The V8 guys use the billet plate or make the 5 speed a 4 speed using 2nd thru 5th. Don't know how that works...

The 901 is having no problems in our car. We take it easy on first gear but give it a hard run thereafter with no issues. The first time I gave 1st a flogging was at the Kit Car Performance Day. Probably should have practiced that a few times before attempting fast 0-60 launches. Went up completely in smoke the first time - tagged the rev limiter TWICE before I got to 2nd. Whatta dufous.

Though spyders are lighter than early 911's, this car has more power than the early 911's. It also has wider tires (except for RS or RSR cars). Newer tires are also stickier, so really, it does pay to be a bit cautious.

angela

Angela,

Thanks for your comments. Can you provide some more?

I have two 901 boxes; a

Oh you know what, Bob? I forgot to mention this - 71-72 transmissions are rather valuable. They were unique to those two years, use the larger clutches and for someone restoring those very collectable years (arguably the most valuable of the long hood cars), these command a pretty penny.

That might make a big difference in choosing the one that you use.

angela

There are two 911 clutch systems, pull type and the push type. Its easier to just go by years, rather than push versus pull because it all depends on how you are looking at it. The the throw-out bearing snaps together with the fingers of the pressure plate in the middle. Both types clutches work off a cable, but their pivot points are really different as are the clutches which is the part that makes one "push" and one "pull". As I've never worked on a 70-71 type, I did a little research to educate myself and hopefully helps you...

I found a really cool thread on the push versus pull type in a 901. It includes a few diagrams that make this a lot more clear and is explained by someone far more knowledgeable than myself. The fellow on the thread named Grady Clay is the beat-all, end-all, porsche guru. If this guy doesn't know the porsche answer, it isn't worth knowing. Further he explains himself really well.

http://forums.pelicanparts.com/showthread.php?s=f0c58df3c52f835239146fa98edd0831&threadid=343838&highlight=901+clutch

Just fyi, the 915 input shaft has different splines than the 901 shaft so those clutch parts are not interchangeable (at least on the earlier 901's - your 71-72 may be a match). The lightest porsche factory clutch that money can buy is a 215mm "S" clutch. But for power, I would suggest going with the 225 71-72 and use an OEM porsche clutch or a KEP. Probably other good ones too, but I've used both of those and been very happy with longevity and performance.

angela

Angela,

Thanks! You

Bob, regarding the RS pressure plate - that could be rather valuable. I've never seen one, so I wouldn't know it from anything else. But Grady Clay on the Pelican BBS site would know. There should be part numbers stamped on it.

We had the "S" clutch in the spyder originally. I loved it. When we went up to the 3.0, I changed out to the 225. With the 3.2, I still have a 225, but now its a Stage II from KEP. Easy to drive but is definately heavier than the "S". That "S" clutch is around $800 complete new... Have no idea what an RS one is worth!

Also, I mistyped above, 70-71 is your box, 72 is 915. You already know that, just clarifying my above statement. Gotta apologize, I've been getting up at 3am to ride my bike and sometimes I'm just not quite firing on all six cylinders...

angela