914 to 915 trans conversion?

[dweymer]

Is it possible to convert a 914 sideshifter to a 901 for a 911? What would be needed? I have 3 complete sets of guts, almost all useable, and they are way cheaper than a 915, and can handle the hp/torque of my stock 2.7. I am not going to ax or drag launch so 1st should last.

[PorscheGuy79]

Donnie, I got one idea to make it work but...well lets say it takes a bit of cutting and welding.

[Grady Clay]

Donnie,

I use a type 911 in my 914-6s. Easy stuff.

Yes, a 901/911/914 can handle a 2.7 on the street if you don’t abuse it. If you decide you ever want to autoX, build yourself a short geared 4-speed or convert to a 915 (expensive).

Exactly what are the three transmissions you have? I can guide you through the process of combining the right parts. Can you post images if we need?

Best,
Grady

[dweymer]

Grady,

I have one complete 914 5 speed, sideshifter, one complete 915(with internal issues) and the internals from 2 sideshifts. Yes on the images.

[Grady Clay]

Donnie,

I recommend you do a partial disassembly on the 915 and photo-document its condition. You may decide to use it, or sell it as complete or in pieces. Regardless, having good photo documentation will help you with your decision and allow a buyer to confidently pay you for good parts.

From the other two side-shifters, what is missing? Can you diagnose the condition (wear, rust, damage)?

Certainly in the Orlando area someone has all the 901 transmission tools. Find them – I’ll speculate there are several.

What access do you have to local Porsche salvage? The most difficult part about used transmissions is the extreme variability in condition. If someone I didn’t know in Florida offered me one for free if I paid the shipping, I would hesitate. Within 15 minutes shop time, it can be determined if further consideration is warranted, even to just pay shipping.

That skill is something everyone on the Forum should have. It takes no special tools to do the basic inspection, a 13 mm combination wrench will do.

Best,
Grady

[dweymer]

Grady,

I dissassembled the 914 myself, and assessed the parts:











I had a BWM/Porsche tech look at some parts to help me learn good/bad on the syncros, sliders, and dogs. I have the fork jig ordered.

[dweymer]

On the sideshifters everything looks good except 1 slider. I know the 915 needs 1-2 syncro, probably the slider and possibly dogs as well. It was run on low fluid so I assume the driveshaft intermediate plate bearing is bad from running dry.

[Clay Perrine]

I have all of the parts that you need to convert the trans. I went the other way and put a 71 911 trans in my 914.

Want to make a straight up trade for all the 914 side shifter parts? I will even pay for the shipping.

[dweymer]

Grady,

From looking at the PET it appears I would need the following:
901.301.031.12 end plate
901.332.209.12 flange (2)
901.302.132.11 shift selector
along with the misc seals.

Clay, so you will trade a sideshift end cover, sideshift shift selector and pulley, and 2 flanges for the following, and pay shipping
901.301.031.12 end plate
901.332.209.12 flange (2)
901.302.132.11 shift selector

If so that's a deal, PM me.

[Grady Clay]

Slow down guys. There is a lot more to this to install a 914 trans in a ’74 911.

One of the biggest issues is the ring gear needs to be reversed and re-set-up. Not a small task and requires the Factory R&P tools.

As you discovered the axle flanges are different. I suspect you are correct but I haven’t researched the P/Ns.

Clearly you need the three shift rails, the shift shaft, shift pivot, nose piece, engine mount & spacers and more. At least the speedometer drive will interchange.

You will need to drill, tap and reposition the breather.


Clutch operation is another big issue. A 215 mm clutch is very marginal with a 2.7 engine - basically unsuitable. You can convert the 914 transmission to the 2.2 (’70-’71) 225 mm clutch similar to the 2.7 clutch. That takes repositioning the clutch release bearing arm pivot, finding all the 2.2 parts (including the differential side cover), and different clutch cable and clutch shaft in the pedal assembly. The 2.7 flywheel will work but you need the ’70-’71 disc, pressure plate and release bearing. The TO bearing guide tube needs to be from a 2.2.

The shifter will have to be changed to ’71 and earlier.

There is probably more that I don’t think of at the moment.


Everything considered, this is not an easy or desirable conversion.

I think you are far better off using your 915 or finding an appropriate replacement. You have good trading stock. I wouldn’t do anything until you assess the condition of your 915.

Best,
Grady

[Clay Perrine]

Originally posted by dweymer
Grady,

From looking at the PET it appears I would need the following:
901.301.031.12 end plate
901.332.209.12 flange (2)
901.302.132.11 shift selector
along with the misc seals.

Clay, so you will trade a sideshift end cover, sideshift shift selector and pulley, and 2 flanges for the following, and pay shipping
901.301.031.12 end plate
901.332.209.12 flange (2)
901.302.132.11 shift selector

If so that's a deal, PM me.

I don't know the part numbers from memory.

You need the end cover. The shift rods that attach to the forks. The guide piece the end selector, and the drive flanges.


I will gather the parts up out of the parts bin and take a picture of them for you. I should have it tomorrow.


Also, Grady is right. You will have to flip the ring and pinion, and move the tranny vent. If you don't move the vent, the gearbox will empty itself of oil within 3 to 5 miles of driving. You have to have new bearings for the differental when doing this.

If you want to pay to have the tranny shipped to me both ways, and for the parts, I will do the conversion for you. I can even install bearings, syncros, or any other parts you want during that time.


The clutch parts are not going to be cheap. The 914 guys want the flywheels for 914 /6 conversions, and the rest of the parts are getting more expensive every day.



I encourage you to think this through before you decide. It might be cheaper to rebuild the 915. It might even be cheaper to sell the 914 tranny, and use the money to rebuild the 915.



And Grady, I have seen a 3.6L 993 motor (and a few Chevy v-8 cars, and one 928 V-8 powered 914) use a 901 tranny from a 914. The clutch is not the weak point. The stress will make the bearing holes enlarge in the case and the intermediate plate. This allows the backlash on the gearset to get larger and larger until it strips off the teeth. The clutch is the last thing that fails.

[dweymer]

I had not thought about the clutch issues...
Agreed Grady...time to open another box.
Clay, need any other 914 trans parts?

Funny how fast one can change his mind when guided by knowledge, and people who have been there, done that.

[Clay Perrine]

Donnie,

I am always on the lookout for 914 parts. The side shifter parts are more sought after, and that is making them more expensive. I have a box full of gears and such, but I can always use another trans, or even parts.

Do you still want the pictures of the conversion parts?

[dweymer]

Probably not at this point. I was hoping, aren't we all, this would be an easy swap! Well I have the insides of 3 sideshifters, and one case.