Inspecting a 901/911 Gearbox after disassembly

[jluetjen]

OK guys, I've got a couple of 901/911/914 gearboxes which have been taken apart and cleaned. What and how do you inspect? For example, one of the boxes I never drove -- how can I inspect the syncros to determine how much life is left on them? Wear on the teeth? What's normal and what requires replacement? The objective is to use the best parts (to save budget dollars for other things) and replace the things that need it. Ultimately I'll be using a mix of gear sets along with a new rebuild kit and a billet intermediate plate (and potentially diff cover) to build up a race gear box.

Thanks!

PS: I'm doing this project now -- so please don't suggest that I wait for Waynes new book!

[Grady Clay]

John,

Get your camera in action and let us see what you have there.

How far apart are the transmissions?

Best,
Grady

[jluetjen]

Hi Grady;
"How far apart are the transmissions?" - 2 out of 3 are completely apart.

Aluminum 901 Box: Still in the car where it will stay for the foreseeable future until I get my engine completely built.

Mag 914 Box: I never drove this box so it's condition was a complete unknown. The case and intermediate plate have been completely cleaned and stuck up in the attic. I have not removed the gaskets from the intermediate plate and case to allow me to mic it in the future. I'm tempted to mic and and write the masurement on the case for reference. The gears have been degreased, wrapped up for now and stored in order in special box for my gears.

Mag 911 Box: This will be my final gear box. I drove with this box once and it shifted wonderfully. The case and intermediate plate have been completely cleaned. The gaskets are still on them for now although I'm not sure how meaningful the measurements will be since I'll be replaceing the intermediate plate with an billet aluminum piece. I plan on reusing the bearings from the existing plate if possible. The gears have also been cleaned and filed.

The final gear ratios that I will be putting into the box (a mix of gears from various sources)...

1st: A (11:34)
2nd: GA (18:32)
3rd: M (22:29)
4th: S (25:26)
5th: X (28:24)

I plan to use as many of the 911 parts as I can since I know that box was shifting nicely. The 914 (and later once it's out of the car) 901 parts will be stored as spares.

What part(s) would you like to see pictures of?

[TimT]

John, if you find an "X" or a gear I can use as an "X" let me know...

I think I sold you my last X gear

[jluetjen]

TimT -- I think that you did too! As you can see, it's found a good home. I've go an "O" (23:28) -- can you swap that around to be a 28:23 which would be one tooth off from being a X's 28:24? Otherwise John Walker seems to have a good selection of gears.

[jluetjen]

Ok; here are some pictures. Fire away!

1st this is the slider pieces off of the main shaft. I believe the 4-5 slider(?). One picture of either side.




Here are similar pictures from the slider which is on the shorter output shaft (2-3?)...




Here's a picture of 1st gear and the associated fork.


Here are pictures of the two other forks.



Here's a picture of the GA gear off of the output shaft.


It's hard to see in the picture, but the teeth are still quite pointy as shown by red arrows.

[jluetjen]

Unlike other projects I've done, I'm trying to repress my baser instincts and be very neat and methodical with my 911 project. Since I don't have any pressing schedule, I've made a point of taking my time and just doing the best that I can with each step. Basically, just enjoy each step of the project as a project in itself as opposed to being so goal oriented that I relentlessly drive to "get it done". Anyhow, here's what I came up with for gear storage...



Here's a picture of the case after cleaning. I've found (based on input from others) that Mineral Spirits works great as a solvent in the parts-washer. It doesn't rust the tank, it does great on grease and the smell isn't very bad -- although it does linger a little bit. About half an hour with a wire brush and a screw driver for the corners and it looks great! (Note that industrial style rubber gloves are a must!)

[Grady Clay]

John,

Looks like a great 911 transmission.

The 4-5 sliding sleeve seems OK but does have some wear. Post side images of the 4th and 5th gears with the syncro in place. Do the 3-4-5 syncros have a scratched grove at the dogs like the 2nd gear has?

Clearly the 2nd gear needs new dogs, syncro, and sliding sleeve.

Carefully inspect the loaded surfaces on the sliding sleeve 3-prong hub for wear or damage. The sliding sleeve must be able to slide smoothly with no restriction from dimples and such.

On the 4-5 sliding sleeve, carefully inspect the inner surfaces that ride over the syncro for wear and any sign of smearing the metal sideways. You will almost certainly see this on the 2nd gear side of the 2-3 sliding sleeve.

While the 1-R sliding sleeve dogs look a little beat up, I suspect it is OK. Post some more pictures and of the first gear dogs.

Post some more pictures of the actual gear surfaces. Experiment with off center very bright lighting and use the zoom function of the camera. The goal is to extend the depth of field and contrast on the gear surfaces. From this image, 2nd gear looks fine.

Radio Shack sells a little pocket microscope. Works great for inspecting every gear tooth.

Show the nose of the input shaft where it goes in the pilot bearing in the flywheel.
Show every tooth on the pinion. What was the debris on the drain plug magnet?

You are going to want to measure the runout of the input shaft and the shift rod.


OK, on to more cleaning.
Measure the paper shim gaskets at the intermediate plate and save some samples. They will measure thinner that the replacement gaskets. Pay particular attention to cleaning around the studs on the main casting. Remove the bearings from the intermediate plate and keep the inner races wired to the side they were originally on. You can use these as emergency spares.
Remove the input shaft seal, axle flange seals, and the clutch release arm & pivot. Do not remove the outer races of the roller bearings or differential bearings unless you intend to replace them – not necessary from what I see.
Remove the breather and drain plug. Is the back-up light switch & pin out? Is the speedometer drive out of the nose piece?

Clean everything again.

Be careful to not scratch the sealing surfaces of the intermediate plate or main casting as those don’t get any sealant. You can, if you feel necessary, put thin sealant on the gasket for the nose piece. I don’t.

Keep the needle bearings and inner races associated with their gears and in the original orientation.

I tend to do a cleaning on the gears and steel parts with lacquer thinner and then with WD-40. Never leave any lacquer-thinner-clean because it will rust. A brass tooth brush works great for cleaning the splines.

Cleanliness is next to Godliness – certainly as far as Porsche transmissions. Cleaning and inspecting is 90% of the effort in a transmission rebuild. Disassembly and reassembly is easy although you will want to triple check everything as it goes back together. More on that later.

Best,
Grady

BTW, can you post links to the prior discussions?
G.

[red-beard]

go to my website

http://home.san.rr.com/pb914/ and review my tech article on the 901.

James

[red-beard]

1st gear slider is in reasonable condition, but the slots need to be cleaned up.


4th/5th slider looks ok, but get the slider off the guide so I can look at the slot condition.

The dog teeth are done. Pull them and replace. They are hammered in the middle. A brand new pair looks uniform radially.

The synch band is also done.

Again, look at my tech article and read the middle section on part review.

http://home.san.rr.com/pb914/rebuild/

[jluetjen]

Hi James. Already have done that. It's been converted to a .pdf along with a similar article that I found on the 914 site and I used it for the disassembly. In fact I now have a 3-ring binder just for the gear boxes in addition to the gearbox section of the factory manual. I'll go back over that and Grady's input when I have a chance to inspect the specific pieces.

[red-beard]

Similar article on 914club? hmmmm.

Link?

[jluetjen]

Actually it was a string of posts with step by step pictures. You know what they say -- a picture is worth a 1000 words.

[randywebb]

This might be a good place to compile all the tips & tricks for these gear boxes.
1. There is a discussion of what should be done to coat or paint the Mg case boxes for corrosion.
2. There is the 915 side cover update that Bill Verburg has posted about.
3. Cutting a groove in the clutch tube to let leaking oil out before it can contaminate the clutch plates.
4. Various strenthening techniques and alterations for the 901/911 boxes.

Grady is on all these threads or on all except #2.

[red-beard]

Originally posted by jluetjen
Actually it was a string of posts with step by step pictures. You know what they say -- a picture is worth a 1000 words.

Geez, that was the preview to the full article...The full article was better proofread, but still not perfect....

OK. - I guess I better get off my butt and finish the book...

[Grady Clay]

Guys,

I agree with Randy, let use John’s three transmissions to compile a really good set of instructions, tips, and tricks on the 901-911-914. We now have THE expert red-beard on board. I’m sure JW and more will contribute. I’ll try and round up some stuff on 904-906-910 that are the same. I have sent some exhaustive e-mails to some owners, I’ll see if I can find them.

For now, let’s focus on disassembly and diagnosis. Of course there is much disassembly that is preparation for reassembly and getting everything back in the right place. I used to have the micrometer dimensions for all the spacer washers. That would be useful to recreate.

This should also include how to set-up both new and used ring & pinion gears and how to make tools “of local manufacture” as Porsche puts it.

As everyone comes across good links or publications, they should be posted.

I will excerpt some of the parts manual exploded diagrams and workshop manual so we can critique and discuss the same things without confusion.

When anyone posts an illustration or image, identify it with your initials, a sequential number, and posting date. This way we can refer to image “GC23 1-12-05” and be able to find it. Reminder to all, if you don’t put © copyright on your image or illustration, it is in the public domain.

Red-beard, it seems you want to write a book. Let Wayne publish it and we can all be contributors.

Best,
Grady

[Zeke]

I used James' (red beard) article to evaluate and rework a 914 901. It was the first tranny I have ever done and it was a piece of cake. I think I'm gonna try to set up ring and pinions next.

That's one article we don't have any info on. And, the most important thing about compiling info for DIY articles is to include any shortcuts or alternative methods that can be employed without having to have every official Porsche tool.

James' article is full of such info and I had to buy only one tool, the big deep socket. And there's a way around that too, I found out later. But at $7 at AutoZone, I'm not complaining.

I set my entire shift fork arrange ment by eye and the thing works like a champ. But, someone has to tell you what to look for to do this. It's tedious and not for production ass'y. It can work; worked for me.