915 Rebuild/Refresh and SSI Questions
 

I have my engine out and 915 separated. I pulled the engine ( first time) due to a clutch failure ( had a separate thread for this). It turns out to be the pressure plate. My engine has 131K miles and still seems solid. Down the road I plan to rebuild the engine to maybe a 3.4 and possibly twin plug etc. but I don't want to do it until the rebuild is needed.

Right now my plan is do a complete clutch replacement including a new flywheel. I also plan on cleaning up the engine , fixing some vacuum leaks I found, replacing engine tin ( pretty rusty) and doing any while you have the engine out preventative maintenance like the head temp. sensor.

I also plan on refreshing or rebuilding the 915 gearbox and possibly installing SSI heat exchangers

The tranny has what appears to be the typical 915 shifting issues from 1st to 2nd. It used to grind until I changed to swepco and readjusted the linkage. I was planning on sending it to Gary Fairbanks for overhaul ( and I still may do that ) but shipping will probably be a pain from PEI to Connecticut and back.

I like to perform my own maintenance/learn as much as possible and am considering doing the 915 overhaul myself but I wonder if it worthwhile or should I just send it out ?

Will I spend so much $ on tools that I might as well have send it out in the first place?

For those who have done it themselves how was the process , would you do it again ? Removing the engine/tranny was pretty straight forward ( but I haven't reinstalled it yet! )

Has anyone used the excellent Pete Zimmermann tutorial on the subject ? It appears to be the definitive document for us would be Do-it -yourselfers.

Also on the exhaust topic would it be foolish to install SSI h/x's on a 3.2 knowing that down the road I will probably be rebuilding to 3.4 and twinplugging. Are SSI's too small for a 3.4 twin plug engine ? Wayne's engine rebuild book seems to indicate this .

The tranny rebuild at home is doable. You can check this site for all the tools and parts necessary. That will give you a cost estimate. The tools are not that much but you will only need them once. Using several publications and articles will give you the best overview on how to do it. As far as what SSI's to get for a modified 3.2 Try the 3.2 ones first with the rebuilt transmission and you might just like what you have and "down the road" might be 10 years!!

Absolutely the tranny rebuild is DIY-able. Cost estimate is difficult, because you don't know what needs to be replaced until you get in there. Mine wasn't too bad, just replaced a few bits here and there, probably under $1000 including tools. The tools aren't overly expensive. Small torque wrench, circlip pliers and a couple specialty things, maybe $200-300. But if there are lots of worn parts, it could get to 1500 or 2000. From the symptoms you describe, it shouldn't be too bad.

When I bought my car in 2004, I didn't know what a carburetor was, or even what it looked like. I had to look up what the fan belt was. I bought it to learn, and learn I have. I rebuilt my 915 in the winter of 08, with just info I found here and various places online. Start a thread, post lots of pics, and you'll get lots of help. It was a great project, and only once or twice did I hit major snags (36mm nut - you'll know when you get there :) ). It was a really satisfying feeling to feel the car move as it should when I got everything back together.

Pay attention to the detents!

some things take an experienced eye to catch although a simple rebuild is worth the shot

Peter Zimmermann- the author of the book "The Used 911 Story" has a great WIKI Tutorial going on the 915 tranny rebuild off his RedLine Technik site. It's broken up into 9 parts. It's a great read on the 915 regarding the in's and out's. It really gives you a good insight if you decide to rebuild the box yourself.

Click the link below:

Porsche Wiki

----------------------
'76 911S

I did mine after a first gear failure, replaced lots of new parts, came to $1500 and it wasnt difficult.

I used this thread:

http://forums.pelicanparts.com/porsche-911-technical-forum/159059-cant-shift-into-first.html

Worked a treat, now I love the trans.

Most of the tools I had or I made using advice from this forum.

I am still tring to decide but I am leaning towards doing it myself. It is really down to the time involved with a busy schedule .

I pressure washed the exterior today to get things ready for the disassembly

I am reading through Pete Zimmermanns tutorial . It is great but kind of assumes you know quite a bit going in and there are not alot of detailed pictures. Once I read the Bentley manual then Pete's work makes much more sense.

The only part I am concerned with is if I get into the pinion bearing play issue that Pete identifies as a weak point in the 915. My tranny has 132k miles so I am not sure if I can expect that issue to come up. If it does it requires outside machining etc. which I will probably have to ship the tranny out for anyway.

Does anyone have a cost estimate on the minimum special tools required to do the job? Replacement parts will be required no matter who does it so the cost of that part really doesn't matter to me.

Thanks

It's kind of like baking bread, you put all the ingredients in but don't know if it works till you bake it or, in this case, it's all together and in the car. If you have any second thoughts, then send it out for rebuild.

You need an old cluth plate. Someone has mine for free so that person should lend it to your for free.

You need 2 sychro tools (maybe at least 1/2 synchro tool)
You need a home made socket for the gear stack (I made mine, and sold it after)
Engine stand, and the proper engine yoke.

Other tools are just what good mechanics have.

Yelcab1 ,

Thanks for the info . I have a couple question on the tools mentioned

Clutch Plate - I have the clutch plate that came out and will be replaced. Is this to lock the transmission ? I thought this could be done by placing transmission in two gears at once.

Sychro tools ($200 for both) - Can get these from our host

Home made socket for the gear stack - What is this? I will need to search this item out. Is there a link to provide more info on this item

Engine stand - no problem will need one eventually anyway

Proper engine yoke - do I need this for the transmission work or only engine work?

Are you sure that you're reading my Tutorial? I worked very hard at making sure that the repair procedure/steps were clear to even a casual mechanic/DIYer who had never done a trans. If you think that more pictures (I couldn't think of a single one that might aid the Tutorial) would help, please list what you would like included and I will consider a follow up chapter based on your input.

The input shaft comes out with all the gears as a unit. The gears are stacked on top of each other and held in place by a big nut. The used pressure plate is screwed to the garage wall, and is used to hold the input shaft stationary. The big homemade socket is used to remove the nut from the gear stack and to reinstall it to the right torque. I have a picture somewhere.

The engine yoke is to mount the transmission on the engine stand while you are working on it. It works for both engine and trasmission.

Custom socket? It's just a 36mm socket, to be used with the biggest effin' breaker bar you can find (torque spec is huge - 200 or something). At least that's what I used. Bought a 36mm 1/2" drive socket, stuck it on a 1/2" drive breaker bar, and attached something to that to increase the leverage. It took all 200 lbs of me (literally, hanging off it) and lots of heat/cooling, but eventually it gave.

The "other" socket...from Part 6 of the Tutorial.

http://farm5.static.flickr.com/4001/...2a9e5e095c.jpg

Torque specs in the Tutorial...

Calling Peter Zimmermann
 

Peter,

The more time I spend reading your tutorial the better grasp I am getting on it . I am not through it all yet. I went back to the Bentley to get a better picture on what the assembly looks like . The entire assembly drawings in the Bentley make it easier to understand your descriptions . Keep in mind that I have not opened the gearbox yet which probably makes the tutorial much easier to understand but since you asked -

I am not suggesting you dumb it down for first time transmission DIY guys like myself but I suspect most first time non-mechanics could be confused with simple steps and descriptions. For example on the first tutorial the following simple steps right off the start lack photos:


"Remove the reverse light switch (22mm box end wrench), the switch activating pin (needle nose pliers), the throttle linkage bell crank (cut and remove the cotter pin), and, if the transmission has one, the small, right-angle metal bracket held by a cover nut just above the throttle bell crank."

Now I know that if you can't figure what these items are you should not go into a 915 but photos of all of the steps described would help . The Bentley manual is similar in this regard where not each and every step is detailed so one gets pretty used to reviewing all resources before tackling the more technical parts of the 911.

Regarding photos like the one below the text :

"OK, the cover is off, and set aside. In front of you, in all its glory, is the reverse idler, on the pin with the o-ring at its end, the small reverse gear (not synchronized), and 5th gear."

Arrows to each of the parts described takes the guess work out of which gear is which when looking at. The following link uses this technique which I find helpful.

TrannyRebuild

The only other comment I would have is that the tutorial appears to rely heavily on specialized tools which I can understand but in reality most DIY mechanics will probably want to search out the homecooked tool substitutions to keep their costs manageable. In addition to the obvious benefit of learning the intricate details of their car's inner workings most DIY mechanics like to save a few $ in the process. From that point of view I thought the tutorial might be even better suited to a real commercial 915 repair shop who can justify the proper tools. I understand if you don't want to go there as the special tools are obviously the best for the job.

Now please don't take my comments the wrong way. They were only meant as constructive comments to help you understand some of your readers . I am a mech. engineer by day and sometimes have to write process descriptions/operating procedures for systems I've designed and I always find it helpful to have someone with no prior knowledge on the subject read my narratives to help identify areas which are difficult for the reader new to a system to understand.

I thank you greatly for your work on this subject along with your other work . I have a copy of your book which I used extensively when buying my 911 and still refer to. I can assure you I would not attempt this rebuild or refresh myself without your tutorial as I believe it is by far the most complete step by step description that I have found. I also understand that the more photos and adding graphics like arrows etc. takes more time and since this is not a book being published its probably pretty hard to justify any more time on the project.

I have a question for you if you don't mind. With a 84 tranny with 132K miles and only typical 1-2 gear synchromesh symptoms is it likely that the "weak" pinion head bearing race/case issue will need work for a proper life extension rebuild. I am not close to any Porsche experienced machinists so that work will be a pain to get done if needed.

Also is the 911 engine yoke required for the transmission or is it a nice to have part. Will the transmission be damaged using just a standard engine stand ( 4point) without the special 911 engine yoke for the tranny work ? I can start this weekend if I don't have to order that yoke which will take a couple weeks to get to PEI Canada.

Thanks

Ross Wheatley

Why are you even rebuilding your tranny? You said it was now shifting ok between 1-2 shifts. All of them need a slight hesitation between 1-2. At 131K miles I think you have plenty of more miles you can put on that tranny before any rebuild. I am talking tens of thousands of miles.

Thank you for your post, Ross, including the kind words about my book.

Your transmission weighs about 120 pounds, so if you can find an ordinary stand that is constructed to handle that weight you will be fine without the heavy duty stand/yoke that you can see in my Tutorial.

Your '84 could go either way regarding the pinion shaft bearing. I've read that there is a cut-off build number for transmissions with the large OD M/S bearing (that will likely have the loose P/S bearing race issue) vs the small M/S bearing (that will likely NOT have the P/S bearing issue), but have found that information unreliable. I can only offer that the later your '84 is in the build process for your model year, the better chance that your trans has the small M/S bearing (I've seen this but have not done enough late '84 transmissions to definitively say that it will be one way or the other). You will just have to open yours up and see what you have.

Regarding tools, so much emphasis was put on tools in the Tutorial because of all the DIYer jobs that can be done on a Porsche 911, the 915 is all about tools. They will make or break the job, simple as that. Like you, my father was a mechanical engineer, and he taught me that there are jobs that can't be done with an adjustable wrench and a battered screwdriver. The investment required for proper tools is considerable, especially when you know that they will only be used once. I appreciate that, but I also appreciate how the luck factor must increase every time that a home-baked tool is used in order to successfully complete the repair of a properly functioning 915.

100,000 miles is my goal; if I do my part (I always try), and if the driver does his part, every 915 will last 100,000 miles+. Unfortunately, few do, and many never work as intended.

I will look forward to your next post.

I'll come to Peter's defense.

Peter has been the most useful on this board when it comes to transmission. The other person is John Walker. His comments are always helpful and perfectly geared toware DIY. He hides nothing, and always is willing to share his secrets. So does John Walker.

On the yoke thing, you don't need it. It is much better to have it though, especially on the assembly.

The $200 syncro tool. Is that to remove the syncro teeth from the gear? If so then I do it with a sharp wood chisel and several hits spaced around the gear. More like $10 than $200. I hold the shaft with a used clutch disc held in a bench vise. Use a new nut and do it back up tight.
Good snap ring pliers are nice but cheap one will work.
Usually the 1st gear downshift crunch needs 1st teeth,syncro ring and 1/2 slider. I would replace 1 and 2 syncros ,maybe 3rd and flip over the remaining one if on a tight budget. I doubt you will have a ring and pinion issue on a SC or Carrera with that street driven mileage.
Take plenty of pictures when dismantling and mark stuff . Box is really fairly easy. Pay attention to the placement of detents and the reverse light switch pin is offset not centered.

Really? I don't think I know anyone with a 911 with fewer than 100K miles and none of them have a rebuilt transmission and most appear/sound to shift just fine.

By the way, a large percentage of 915 boxes have spun bearing race.

With such great response to my questions from such helpful and knowledgable people on this forum, I decided to tackle the job myself. Will start the teardown in the next couple of days. Finally and excuse to buy that engine stand.

My wife will not be pleased as I am supposed to start building a new set of Kitchen cupboards soon for a reno to our house she has planned for this winter. I guess that will give me a reason to get this tranny work completed in a timely manner. Being a chronic DIYer can be a real pain for those around you !

Is the spun race on the pinion bearing obvious when one gets in there ? Is that repair possible be any decent machine shop with some direction from the good folks on this forum ?

Ross

Oh, Kurt, the stories that I could tell you! I've done heavily damaged 915s with fewer than 50K miles, I've done 915s broken by valet parking "technicians," I've done a big number of synchro repairs on 915s with fewer than 80K miles. My shop had an active clientele of more than 1500 P-car owners, and 95% were 911s. A high percentage of those were from the 1972-1986 group fitted with 915s.

Please remember, I'm from L.A., where traffic congestion is the norm, and three shifts/minute is not unusual. I'm sure there are parts of the country where three shifts/thirty miles is more the norm. 915 life expectancy all comes down to driver technique and shifts/mile. When I write that 100,000 miles is my goal for every 915 that I repair, I'm writing from a Los Angeles point of view, not the mid-west countryside.

A loose pinion shaft bearing race will be very obvious. In extreme cases the race will pull loose from the diff housing as you pull out the pinion shaft. In milder cases you can put your fingertips inside the race, expand them like an umbrella, and turn the race.

I've only used one machine shop, a very diverse and talented group of guys, to do this repair, so I can't speak for other shops.

Point well made Peter! SmileWavy

I have good friends in MO, IN, and MN - it must be so much more fun to drive P-cars where you are than in L.A.

In summer, anyway!

My 915 with 75k on it had a spun race, needed most of the pinion and mainshaft bearings (badly pitted) and syncros and dogteeth on 1st, 2nd and 3rd. It wasn't worth the cost to even try to rebuild it at home. Just ended up getting another unit that had been rebuilt by someone who had the tools and experience.

gtihop,

What was your 915 like to drive before you replaced it?
Where did you get your rebuilt 915 ? And did it turn out to be a good one?

Also if you don't mind me asking , what does it cost for a properly rebuilt 915 ?

I know if I open mine up I will likely replace all of the parts recommended by Pete Zimmermann in his tutorial as I hate to do something twice.

I have a do it right or don't do it at all attitude to things like this which tends to cost me money.

I can always open it up do the inspection and make the final call but I believe in a tranny with 132K miles like mine, Pete Z. suggests all bearings , synchros, most dog teeth etc. be replaced for his 100K mile goal. In my reality I only put a few thousand miles per year on the car but I am planning on increasing the power down the road and will probably put more stress on the tranny once I get that work done.

The pinion race repair would likely put my cost way over the cost of a rebuilt unit so I may need to take a hard look at it when I get in that far.

I put together the engine stand last night so I am ready to mount the tranny and open her up this weekend.

Ross

Let me try to modify your thinking process just a little bit. You're saying that, based on repair cost, you would consider a "rebuilt" 915, rather than fixing yours by doing what's needed. That means, if I'm right, that you would consider paying less for a "rebuilt" than what you could fix yours for. Are you aware that "rebuilders" out there don't fix the loose pinion bearing, instead, they throw a little LocTite at it (or peen it) and hope for the best. Hope doesn't fix a 915 bearing race problem, and your new "rebuilt" might have a loose bearing after the first heat cycle you put the trans through. Not all rebuilders hide this type of "fix" (see below) where eyes can't see it, but some do. Often, a "rebuilt" 915 is cheaper for a reason...or reasons.

http://forums.pelicanparts.com/uploa...1284087549.jpg

http://forums.pelicanparts.com/uploa...1284087600.jpg

Thanks for the reminder Peter but if you read my posting closely, I note that price query on a properly rebuilt 915. I would only be considering one from a highly respected rebuilder with the reputation to back it up.

I suspect a properly rebuilt unit may be pretty costly but it would be nice to know this number if I find the problem.

With this pinion issue in the 915 being the only real weak point as you say, do you always make this repair regardless of the condition you find the pinion race in . I would think for the 100K mile goal you would have to address this regardless of the condition upon inspection. Maybe a new bearing will address the issue for another 100K if the race is in good shape ?

In your pics are the punch marks the rebuilders quick fix ?

This is the "after" condition of a repaired diff housing...note the steel ring that the new race has been pressed into.



http://forums.pelicanparts.com/uploa...1284091940.jpg

what Pete shows above is one of the proper way to fix this. A newly designed clamp plate by someone in San Carlos is another very good, permanent, and expensive way to fix the spun race.

There is a less expensive way that someone else on this board was able to provide. Knurling the race or plating the race and then pressing it back in. I know that a racer probably would not do that. It may or may not last 100K miles but the original did not last 100K miles either.

Thanks folks for the clarification on the proper repair technique.

The steel ring insert looks like a fairly straight forward repair. Is the ring and machining dimensional information commercially available for this repair so that it could be passed along to any quality machine shop to have executed.

I suppose the trick to this repair is getting the housing alignment correct in the machining equipment so that the new ring and bearing is in correct alignment upon reinstallation. It is probably not easy to do that and probably where shop experienced in this particular repair is required.

Ross

The machine shop will have to know how to index the old bearing hole (to find its center), then they will have to machine the hole to its new OD. Then they will have to know what steel (for the new ring) to use, and how much press to aim for (heat the housing and press in the ring), followed by the appropriate press for the bearing race into the support ring. The job is done in a vertical mill.

If you do find a loose bearing you always have the option to ship the diff housing and new bearing race to Los Angeles. If you decide that's OK, pm me and I'll give you the shop info.

Spun Race
 

Opened things up today. Everything came apart quite easily. I used the " 2 gears at once" technique to lock the shaft. It seems pretty common so I thought I would do that to save the time to make or locate a proper shaft locking tool.

I believe I am the first one into this 915 as the gaskets looked original. There was nothing but the gaskets on the sealing surfaces.

I followed Peter's guide for the most part except for the shift fork removal part in intermediate housing. I kept those intact per the threads recommending this by John Walker to keep reassembly simple.

I will post some photos of the gears but I did not notice any broken or severely warn dog teeth. The very tips appear to be slightly rounded My PPI indicated a gearbox that was probably in pretty good shape except what is probably worn synchros. I do not know how to tell if the synchros are worn . I guess that will be determined later when I disassemble the shaft stacks .

Unfortunately the pinion race has spun as feared. It turned quite easily with greasy fingers . If you didn't know better one would think that the race was supposed to turn as it was so smooth in its oil film. I was able to remove the race with my fingers but it is not sloppy if that means anything.

I also see that there is some wear on what I think is the 1st gear (small gear). I have no idea how much wear is expected here.

http://forums.pelicanparts.com/uploa...1284250692.jpg
http://forums.pelicanparts.com/uploa...1284250790.jpg
http://forums.pelicanparts.com/uploa...1284251671.jpg
http://forums.pelicanparts.com/uploa...1284252056.jpg
http://forums.pelicanparts.com/uploa...1284252121.jpg

Now I need to sort where to go from here since I guess this is definitely not a good situation to be in. I am not sure what is a good or bad looking 915 when you open it up.

I know I want to fix it right. I want to close this thing up knowing I have a 915 that I don't have to be worried about for many years of spirited driving.

I took quite a few photos and can load them up for all to see.

I guess I should continue the dissassembly or should I put it back together and ship it off. I did not find it difficult to take it apart to this point but I know I am just starting the process.
Comments please .

Take it all apart. Inspect the gears and synchros (the synchros are measured in the installed positions). If they are shiny, then they are likely worn out. Inspect the dog teeth. Inspect the sliders. Send out the intermediate housing to fix the bearing. Inspect the bearings. Replace what is worn, and put them all back.

Thanks Yelcab1

I should have no trouble taking it apart it will just be the diagnosing if parts are worn and need repair. Hopefully posting photos of the gears will help.

Does anyone have an east cost machine shop recommendation to get the bearing race repaired?

The questions over the coming days may look pretty silly to the experienced on this forum as this is the first time I have ever had a gearbox apart before so I am pretty green when it comes to this repair.

I was hoping I would not have to open the differential housing but I guess I am just not going to get off easy on this one .


Ross

Be sure to check the bearing shell in the intermediate plate....

I have question about a step I forgot to do when I took the shaft assemblies out of the case.

I forgot to remove the shift rod detents first . Is this a problem . I suppose it just made my effort greater but the assemblies still came out ??

It is mentioned by all the experts so I wonder if it caused damage not removing it.


Ross

More Questions and Some more pictures:

The pinion shaft came apart with a few whacks per the John Walker technique - all except the pinion bearing. How do I get this off ? If I am to perform the spun race repair a new bearing may be on order and I need to be able to get that bearing off the shaft

http://forums.pelicanparts.com/uploa...1284428657.jpg


I still need to get the input shaft nut off and dissemble but so for I have these apart:

5th Gear:


http://forums.pelicanparts.com/uploa...1284429117.jpg
http://forums.pelicanparts.com/uploa...1284429134.jpg
http://forums.pelicanparts.com/uploa...1284429161.jpg

1st Gear:

http://forums.pelicanparts.com/uploa...1284429194.jpg
http://forums.pelicanparts.com/uploa...1284429234.jpg
http://forums.pelicanparts.com/uploa...1284429261.jpg

2nd Gear:

http://forums.pelicanparts.com/uploa...1284429298.jpg
http://forums.pelicanparts.com/uploa...1284429320.jpg
http://forums.pelicanparts.com/uploa...1284429343.jpg


So far I plan on replacing all synchro rings and the associated break bands as well as the 1-2, 3-4 sliders . I guess I should be replacing the 5-R slider as well what do you folks think ?

The bearing races for 5th and 1st appear fine to me - no pitting or lines so I was thinking about reusing most bearings to try and keep costs under control (unless I can find a more economical source-are the 915 bearings available for most bearing suppliers ?)

The dog teeth look much better than most I see pictured on this site under rebuild threads. Do these dog teeth warrant replacement due to wear or is it just recommended practice because I have the system opened up?

Comments ?