Hey,

I just purchase a 914 - 6 with a 2.7L CIS engine (just rebuilt) and a 915 tranny (just rebuilt)

On the first drive the 915 gear box pushed alot of oil out the vent. It seemed to "crunch" going into 3rd gear. But it has a real crappy home brew shift linkage on it. Im going to replace it with the Wevos system.

My question is, when flipping the pinion gear in the diff to use this tranny in the 914, it there some other mod that is need to control oil flow?? Or can you just flip the pinion, set it up and be done with it.

Cheers

Enigma

Flipping of the Ring gear should have no appreciable effect on the oil level or venting. You may want to check to make sure the vent is pointed in the right direction. It should be facing the back front of the car in a 914, with the hole going away towards the bellhousing. I know it sounds strange, but they will hemorrhage a lot of oil if the vent isn't properly oriented.

If $2000 for Wevo isn't in the budget you can do a cable shift that works pretty well for considerably less. It isn't quite as good, but worth considering if money is tight.

edited- Thanks Paul

Here is a link showing all the work possible for a 915 transmission. In it he shows the clearancing he had to do "flip" the carrier.

http://www.914club.com/bbs2/index.php?show...751&hl=wevo

Great thread link Wes! Lots of good info.

This is not really accurate. The vent has a taper cut in the part that sits in the tranny. That taper needs to face away from the flying oil off the ring gear. Here is a picture that shows the stock 911 installation. The 914 rotates the other direction (shown in red) and oil would come out like a garden hose. The vent needs to be reversed 180 degrees or hole aiming forward.
Click to view attachment

Hey Guys


This is great information! thanks greatly!

Now to solve the 3rd gear crunch!

Any suggestions?

See what I get for being lazy, the 911 was closer than the 914. That's the first I've heard of changing the vent orientation when flipping the R&P. Makes perfect sense though. Nice Diagram. I checked my 914 running a 915 with flipped R&P and it is indeed pointed towards the bellhousing as Paul indicated.

It is one of those things you are told that must be, and now I understand why.

Is the 3rd gear crunch new? You might be low on oil, what with it spraying everywhere...

Well, its only got 25 miles on it since it was rebuilt, and to add further fog to the matter I just purchased this car. There really isnt any substantial historical info on it other than a local porsche tech rebuilding it.

It could be low on oil, but it crunched right away. Very diffcult to get into 3rd, when you do find it, you get that wonderful (!) crunching of gears sound.

If I can figure out if its the crappy shift linkage, I have no problem in buying the complete wevos system to sort that out. I just dont want to spend all that doe to find out the tranny is toast.

What do you folks think of reverting to the orignal 901 side shift? This car has a stock 2.7 Litre CIS motor in. Will the 901 hold it ok for the street?

Cheers

This is one of those questions where you'll get a lot of different answers.

Your motor has roughly 165 ft lbs of torque which by most accounts is well within the reliable operating range of the stock 914 transaxle on the street. Conventional wisdom is that they are quite reliable up to the 3.2L carrera motors which generate around 200 ft lbs of torque.

In reality there are 3.6L engine conversions and V8 conversions doing quite well with stock transaxles. Some care must be exercised at that level to prevent breakage, but contrary to popular belief they don't turn into dust. The bigger issue becomes the stock gear ratios at that point, but with a CIS 2.7L the stock ratios should be fine.

Ok Great info thanks. Is there a big difference between the 901 and 915 in ratios? Is this info posted somewhere??

I just broke down and ordered all the Wevos stuff. The tranny is still kinda under warranty, so if it still crunches after the shifter woes are sorted out, Ill pull the tranny and take it back to the guy. I figure since Im this far with the unit, I may as well push on and keep it. (flywheel, clutch disc, pressure plate etc) I really dont intend to leave the 2.7 stock anyways. I read a great paper on adding 9.3:1 pistons and 964 profile cams that give the motor some real snap. Hence the 915 tranny will probably stand up to that type of service better.

Cheers

These have some basic info that might help you understand the differences between the two...

http://www.roadglue.com/wiki/index.php/901_transmission

http://www.roadglue.com/wiki/index.php/915_transmission

It would be crazy to go back to a 901 if you have the 915 already. The nice thing about a 901 is that they are cheap, shift a little easier than a 915 and it's easier to fit a muffler behind one. It ends there though.

Either transmission costs a lot to rebuild. If you stick with a 915 it will handle the future upgrades. It's the torque that kills the trannies. High HP and low torque will work with either. Also the more cylinders you have will be easier on the tranny (given the same hp/torque) since there are more firing pulses and less opportunity to relax/load the input shaft and I believe why V-8's can run suprisingly long with a 901.

Re-gearing either tranny is expensive but if I was going to do it, I would certatainly only do it once using the 915.