902/1 Trans Questions

[spinmd]

I've got a very nice 902/1 transaxle, serial # 222127, 14/65, AFMSX gearing, and was hoping I could get some assistance with it. Here are my questions:

1. Is there a way to tell if this was installed in a 911 or a 912?

2. Does it matter? That is, are there any quality differences between the 911 and 912 versions of the 902/1 trans that would make it unacceptable for install in a '69 2.0 911E

3. Will I need to change the CV flanges to fit this into my '69E?

4. Is changing out the CV flanges a simple job of removing the center bolt, sliding 'em off, sliding on newer (108mm?) flanges, then bolting them in?

5. I believe this is a non-simplified differential and should be good to go without any differential mods. Correct?

6. What can I expect from the different 5th gear, X (28:24) vs. the Z gear (29:23) of the original 901/13 tranny that came with the '69E?

Thanks,

[Grady Clay]

I've got a very nice 902/1 transaxle, serial # 222127, 14/65, AFMSX gearing, and was hoping I could get some assistance with it. Here are my questions:

1. Is there a way to tell if this was installed in a 911 or a 912? No, not without going back to the original CoA. I don’t know if PAG/PCNA can reverse lookup numbers. Your number 222127 doesn't fall in the Spec Book range 220001-221721 901 to July '65, 234001-238942 4-cylinder, and 130001-131571 6-cyl.

2. Does it matter? That is, are there any quality differences between the 911 and 912 versions of the 902/1 trans Not if you put it in an ’68 and earlier car.
that would make it unacceptable for install in a '69 2.0 911E only if you can find the relatively rare axle flanges used on a 901/13 and convert the differential to the later updated simplified differential from a ’69.

3. Will I need to change the CV flanges to fit this into my '69E? Yes, and more.

4. Is changing out the CV flanges a simple job of removing the center bolt, sliding 'em off, sliding on newer (108mm?) flanges, then bolting them in? No, not in this case.

5. I believe this is a non-simplified differential and should be good to go without any differential mods. Correct? No, There aren’t any Porsche axle flanges that fit both the non-simplified (’65-’67) differential. I suppose you could have them made - $$$$$).

6. What can I expect from the different 5th gear, X (28:24) vs. the Z gear (29:23) of the original 901/13 tranny that came with the '69E? The X-5th is about 20 mph/1000 rpm (3000 rpm = 60 mph) with standard diameter tires. The Z is 8.07% taller ratio (2775 rpm = 60 mph) with the same tire.

What is amiss with your ’69 transmission? It is probably easier to re-gear your ’69.

Best,
Grady

[304065]

902/1 is what I have in my '66.

Punch AFMSX into a gear chart, you can see that it's different than AFMSZ or even more, AGAOVZA from '70 on. The additional torque and HP of MFI gave the '69 longer legs.

[spinmd]

Wow! And bummer. Thanks Grady and John! So, it looks like I've purchased a tranny that won't work in my 69E without spending some big bucks. I purchased it as it appears to have been completey rebuilt by Ross Motorsports (Indiana) and still has the rebuild tags with the "Add Oil" note on it. But, perhaps it might be only valuable to tear it open and use/save the gear sets for a 901/13 that needs some attention.

Right now, I'm collecting parts to put my '69E back together and made the wrong assumption that this tranny would be a better substitute than the modified 914 tranny which it has now (who really ever looks at the ribs on the bottom of a tranny anyway)?

Just curious Grady... why would I want to revert back to the simplified differential? Is it because that is the only way this tranny would fit in my E?

Thanks,

[Grady Clay]

Ron,

The simplified differential with the upgrade (armature, roll pin, etc) is the best choice of the open differentials. Better than the non-simplified.


Do you have a 901/13? If so, what is wrong? What do you know about the 902/1 rebuild? What new parts?

A 902/1 has the non-reinforced (12 mm threads) “F” input shaft/2nd gear. The 901/13 has the reinforced 14 mm threads) “F” input shaft/2nd gear. I would dismantle both transmissions, gear the 901/13 AFMSX with the reinforced shaft and update the simplified differential. I would put all the best or new parts (bearings, syncros, sliding sleeves, engagement dogs, etc.) in the 901/13.

A potential difficulty is if you find a non-serviceable ring & pinion gear in the 901/13

I would carefully photo document and measure everything in the 902/1 Then assemble for protection but not to run (you can leave the pinch bolts out of the forks and leave it in two gears.) Cover everything with really heavy gear oil. Mark the transmission with a tag and paint stick.

If/when you sell the 902/1, you and your buyer will be well served with real numbers, good high res images (in focus) and he will want to inspect and rebuild himself.

This combination will get you the best (and original type) transmission for the least money for the 911E. The 902/1 would be appropriate to keep with the ’65 engine. I would also try and score the complete set of Solex 40PII for it.

How far apart is your ’69E Coupe? How close to original – or not - are you shooting for?

Best,
Grady

[spinmd]

Hi Grady! I really appreciate your insight as I've been following your posts and knowledge for some time. I have absolutely no experience opening a tranny or an engine, but bought a few trannies and have two complete '69E engines I'm hoping to gain some experience on -- a bit scary though. I completely disassembled the E in '85 and had it resprayed and then I put it all back together; it's now in pieces again waiting for a more thorough restoration. I do have experience in typical mechanical things like removing the engine/trans, R&Ring the clutch, carbs, suspension, brakes, etc.

My E is pretty much a totally original, rust-free (other than the edge of the driver's sill), California car, however, the engine & trans are not COA stock. A valve blew in the late 80s and I made the mistake of selling the blown engine since I was young, the cars weren't worth much then, and I didn't know any better. It's now got a 1965 engine that ran quite well prior to removal but when I bought the '69E someone had already swapped out the trans for a modified 914 trans. Other than the 914 trans, I've got the new '65 trans and two other core trans that I need to take a look at the model/serial to see what they are (one has a bent drive/input shaft). I'm almost 100% positive that I DON'T have a 901/13.

I'm shooting to get my '69E coupe back to complete original (other than the engine/trans). It has had no mods other than putting in Euro lenses and black horn grills. Its got the five deep dishes, original seats, Koni (wedge-pin) replacements for the Hydro pneumatics, turbo tie rod update, etc. I don't have the door pockets -- who does? . The repaint was done in original burgundy base coat/clear coat but needs to be redone -- I don't recall the Porsche name for their burgundy.

I don't know much about the 902/1 rebuild. It was shipped to me packaged bolted down in a wooden crate, with the 'toe tags' showing the gear ratios, rebuild date (last year), and the 'add oil' note. The input shafts (clutch and shift coupling side) are taped, the speedo drive is taped, and the accelerator/bell shaft is taped. The gaskets are brand new all around, it's completely clean (shines), and the bolts look new. One tag says Ross Motorsports and it came from Indiana. I believe RM used to be well known for Porsche work before closing up shop. I bought it to either match up with my '65 engine and sell as a set; use it in my '69E as is (which you've noted will not be feasible); or gut it for the gears, synchros, etc., to put into a 901/13 since I am hoping the internals are either new or very good condition.

I've got the dual fuel pump for the '65 but was running 40IDAs. I've been on the lookout for original Solex carbs but haven't put too much effort into it since I haven't ascertained whether having them with the engine will help increase the resale value vs. the cost of obtaining them. I also have a burgundy (painted purple by PO) '71T Targa that I'm considering putting the 40IDAs on once I get the '69E engine up and running with the MFI. These are all projects that I want to get to ASAP but I've got home remodeling, landscaping and numerous other 'to dos' that are looming in front of me.

Since I'm a bit concerned about destroying a transmission with a failed rebuild, I'm considering hiring it out. I don't have any specialty tools but am willing to buy what is needed if it won't cost an arm and a leg. It's getting difficult to find skilled folks that can do a proper tranny rebuild (especially in Iowa) and I've always thought it would be something good to learn -- my father-in-law says it's easy; but he's never opened up a 901 before.

If I gut the 902/1 for its internals, would an empty case have any value to keep with the '65 motor? It looks like I've got a lot of reading and learning ahead of me. Too bad there isn't a book on tranny rebuilds like Wayne's engine one -- that's going to be my bible when I crack open the E motors.

[Grady Clay]

Ron,

You won’t have any difficulty with a 901 transmission rebuild. The very few special tools are easily made and not too expensive. There is already a lot of detail posted. We can guide you through every detail. One important issue is your being able to take really good images. This will allow us (at distance) to use the “practiced eye”. You will NOT have a ‘failed rebuild’.

The R&P is another story. That takes expensive specialized tools and high skill.

I recommend you go on a web scouting expedition for a complete, good used 901/13. Sooner or later you, or someone 70 years from now, will install the original type. It might as well be you and sooner while they are reasonably available.

With a 901/13, all you need is an “X” 5th gear to achieve the AFMSX ratios. That gear pair is readily available good used and inexpensive. It may turn out you already own one in one of your cores. Same with the simplified differential update. I’m pretty sure it is in your 914->911E transmission.

What is the condition of your 914 transmission in the 911E? Do you know what is inside? Is your original 911E parts or 914? The usual reason for this conversion is the original simplified differential destroyed the 901/13.

I recommend you get, make or buy the basic 901 transmission tools. Set up a work area and buy a roller shelf dedicated to transmissions.

The first projects are to carefully disassemble and document your core transmissions. This will let you see how easy this is and hone your skills. It will also let you document the condition of all the parts.


OK, change hats.


With all the information and help of the Forum, you won’t have any problem rebuilding the 2.0E engines.

From your descriptions, you have one reasonably running original ‘69E engine and one complete spare (condition?). Before you do anything, perform some diagnostics. You can do a cylinder leak test on non-running, out-of-the-car engines. Other include sump plate inspection, inspect inside the valve covers and chain covers. You want the best information possible before you light into disassembly or continued use.

If either or both engines inspect OK, you may be able to find someone with a similar chassis and work a deal to get his car running and test and run-in your engine(s).

An important feature of putting an MFI engine rebuild back in service is to know that the MFI will work when you first attempt to start the engine. I recommend you keep your running engine running and get every little detail of the MFI and ignition in perfect condition. Take it off and preserve it for storage. Now install the ‘other’ MFI and ignition and repeat the process. This lets you have known good and proper functioning components to use trouble-shooting.

I would keep one engine properly running continuously and the rebuild the mechanicals of the other.

You are going to find some rebuild parts difficult to buy. Generally speaking, if you can buy NOS parts that you will possibly need and not pay exorbitant prices, you will be well served in the long term.

Another important track is to buy many salvage-level period cars – if the price is right and you can store/preserve them. Porsche didn’t build many cars in this era. PAG/PCNA has chosen not to fully support them with new production spare parts. The ‘aftermarket’ is still OK for some items.


Change hats again.

You now have a complete ‘65 engine with Webers and some Solex parts. You also have a ’65-’66 transmission with a fresh rebuild. It is your decision to keep them or sell. I suspect some would give their left n$t for them now. On the other hand, you can slowly complete them in all detail. You then have something far more valuable or can use them yourself in a ’65-’66 chassis. There are pros & cons to either.

Do all this in balance with job, house, family and a life. Everything in balance.

I hope I’m not being too preachy. I have been doing this silliness since before these cars were new. I did this professionally for 23 years. Sorta like your local Porsche ‘bartender’, family counselor, business & career advisor and Porsche tempter.

Best,
Grady