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Newbie with 915

Posted: Mon Oct 02, 2017 12:34 am
by Clatter
Just took apart my 915 transaxle for the first time..

It had been 'gone through' by a shop,
But I had little confidence in them.
Thinking it was a good thing I did so.

The shim that controls the pinion depth,
Right under the bearing housing (That's what you call it, right? :wink: ) Was a bit mangled.

Image

The only part of the shim that was really damaged was where the pinion bearing interfered.
Perhaps during a previous disassembly..?

It looks like the 'functional' part of the shim,
Where it controls the pinion depth, is OK.

Maybe I could trim it up a tad, clean it up, and run it?

Not that I'm trying to save money,
But I'm scared of messing things up.

Is there any particular story about replacing this shim, besides getting the right thickness?

Measuring it, it comes in around .0043"
But, because of it's crusty condition, it could be a few tenths more, or less..

Let sleeping dogs lie?
Signs of impending doom?
Hoping this isn't part of some expensive self-destruction scenario..

The races (especially pinion bearing) seem really tight in their bores, FWIW.

Will need a rebuild gasket set, O-rings and output shaft seals.
Who would you get these parts from?


Any wisdom from the old guard would be most appreciated.
Feeling a bit 'in over my head'!
:oops:

Re: Newbie with 915

Posted: Mon Oct 02, 2017 7:31 am
by Pablo2
You obviously need a new or good used shim. That one's ridiculous.

I also highly recommend a 1-piece bearing retainer, as is used on virtually every quality rebuild, and as came standard on all models after the 915. The fact that your bearing races aren't loose is wonder in itself, and the retainer helps keep them that way.

I'll ask about a good used shim at German Transaxle today (again, are you saying it's barely over .004" thick?). I can steer you toward the other parts you need via private PM. I note you're in SC, so easy enough to mail stuff to you ..

Re: Newbie with 915

Posted: Tue Oct 03, 2017 5:06 pm
by Clatter
Wow, thanks for the reply, Paul.
Very much appreciate your sage advice.

After reading my eyes off,
it is starting to make sense what needs to be done here.
Will need that dual bearing retainer, some nuts, and whatever gets found to be bad..


1St, re-measuring the shim, it indeed is .004", so .1mm.


2nd, how to approach this.. (Hope you have a minute to read a long post here - apologies in advance).

This particular trans is actually a 923 out of a '76 912E.
It was purchased after the car had an engine fire, and was totaled.
Then, the wrecking yard dropped it from way up high, breaking the nosecone.

It was sold to me as a very low-mileage original trans.
They claimed it had only like 80K on the clock, or so.
Supposedly it was driven by a dentist's wife.
(Junkyard tow truck driver story, no doubt). :roll:

Anyhow,
Because mag is flammable, and it was getting a bug@5-speed nose cone anyways,
I paid a local Porsche/Audi/VW high-end shop to 'go through it'.
Wanted to know if it was damaged in the fire, had been re-built before, if they thought the story was true.
It came back later, with them saying it was indeed a perfect low-mileage 923, and they were the first to open it.


After having it for a while, never even putting oil in it.
I got up the courage to open it up myself.
Obviously, looking at that shim, it was a good idea.

The other thing about it, was that it was dirty.
Inside especially..
There is a grit all over from dirty hands and/or lying on a dirty bench.


So,
On to my question..
Before, with rebuilt beetle tranaxles.
There's this "they're never quite the same after a rebuild" thing.
None of the rebuilds I ever had shifted as effortlessly, or were as quiet as an assembled-by-VW original.

What I would like to try here with my 923 is to clean and save everything OG if at all possible.
If the story about low miles and never apart is true, then this *could* just go back together, and be nice as OG.
Right?

That's why changing out that shim had me all squeamish..

I plan on popping apart all of the stacks, and opening the synchro assemblies,
And see if it is all indeed as nice as it is supposed to be,
With an eye on cleaning it up, and putting it back together like it was.


Would moving to the dual bearing cover require me to re-set the R&P?
Are the new bearings likely to be as nice in quality as the OG ones?
Remembering that the 912E had a feeble smogged-out 4-banger, unlike any of the sixes the car was designed for,
Maybe bearing replacement isn't SOP here.
(Or even the dual bearing cover?)
My motor will be a type 4, and unlikely to ever be over 200HP.



Could I just take the entire gear stacks, and put them in the parts washer?
(Citrus/water washer like a dishwasher)
I would be blowing them off with compressed air right away,
Lying them in the sun to dry,
And maybe hosing them down with some WD-40.

This would make the dis-assembly/inspection process far more fun..
(Sorry if this is a dumb question, I heard that synchro coatings could react to solvents).


I also want to get the burned-on oil/grit removed from the outside of the case by vapor (wet) blast.
Should I just mask off the 5/R detent assembly,
Or do I dare drive out these roll pins and take this apart?
Image

Again,
Thanks for tolerating a barrage of newbie questions.
I'm super excited about this,
And,
Been having really good luck so far! :D

Re: Newbie with 915

Posted: Wed Oct 04, 2017 10:20 am
by Pablo2
Clatter, it's been literally 30 years since I've been into a 923. I played around with "slick-shifting" one for a dragrace customer (no easy feat, due to the odd number of engagement dogs, and the manner in which the spider mates with the slider) before steering him toward the more reliable Type II transaxle.

I checked with a rebuilder local to me, and the thinnest shim in his collection was .010", and it wasn't in that much better a condition than yours. I'd advise your calling around to get a new shim. Pelican Parts is a place to start, or perhaps the Porsche stealership. The design (which requires these thin shims) should have been improved to use only thicker shims with a wider range of sizes (like they finally did with diff shims in the late model Porsches).

I dug through my meager Porsche parts bin and found the 2-piece retainer we used to make https://www.thesamba.com/vw/gallery/pix/1698190.jpg .. actually, my old business still carries them. It doesn't change the shimming, but it makes assembly a bit trickier. The mod is well worth the effort, though ..

Unless I'm mistaken, Bruce is familiar with this trans, having owned a 912. Most things about it are the same as 915, but I'm far from an expert on earlier Porsche transaxles .. however, I'll dig up a photo or two of things I do to make the Porsche-style sliders more reliable. I'd be taking a real close look at all the synchronizer-related bits, as I'm not seeing a low mileage trans from your pics so far.

Re: Newbie with 915

Posted: Fri Oct 06, 2017 11:21 am
by Clatter
Thanks again for the wisdom, and checking for me Paul.
Will start fishing for parts..

The 923 was supposedly the same as the 915 for '76 with two exceptions:
1. Push-type clutch like Beetle/914, vs. pull-type for 911.
2. Close ratio gear-set for use with small 4-banger - same as 2.7 RS for the same year.
(For this reason, it is supposedly rare to find the gears still in the box - as they are often scavenged by racers).

This is kind of turning into a build thread,
So I'll give some credit to the other sources.
This is a great 'how-to' 915 rebuild - Peter Zimmerman of Red Line Service:
http://porsche.wikidot.com/porsche-915- ... r-tutorial

A guy 'Gordo' on Pelican just went through the process, and documented well:
http://forums.pelicanparts.com/porsche- ... build.html
This one has the added advantage of home-made tools and workarounds.
As well as an eye for what -needs- to be done vs. -wants-;
Because I don't have a reputation on the line, and it's my own ass that will have to get under the car and pull the trans,
I can afford to try and push the limits of cheapness a bit, dig?

There is also a bunch of 901/915 stuff on youtube.

Here is the first expensive-looking problem - 5th gear slider sleeve.
Ugh.
Guessing this one is a goner?
Image
Image
Looks like the dentist or his wife was lugging 5th?
This guide sleeve(?) too?
Image

Weird, though..
Someone is selling a similar one on ebay,
And calling it "good used"??
http://www.ebay.com/itm/NICE-USED-ORIGI ... pL&vxp=mtr

Are the teeth looking OK?
From what I can tell, they aren't supposed to be pointed sharp at the tips?

Image
Image
Image


While probably not the low-mileage box I was promised,
Maybe,
Just maybe,
I'll get away without spending $2500 is parts..? :|

Does it maybe look like perhaps we have some mileage,
And not the most religious fluid changes,
(And some lugging in 5th),
But no hooning - bang-shifting - or teenage/track use?

Hopefully?

I'll be getting the shafts apart and everything cleaned up here soon.
Then we'll know the real story.

Any thoughts about this based upon what we can see so far?

Am I doomed to paying credit card interest fees for the next several years? :(

Re: Newbie with 915

Posted: Fri Oct 06, 2017 2:52 pm
by Bruce2
Clatter wrote:
Fri Oct 06, 2017 11:21 am
Here is the first expensive-looking problem - 5th gear slider sleeve.
Guessing this one is a goner?
Image
No, it is made that way.

You should clean your parts before passing judgement. All that gunk between the engagement teeth obscures the wear.

The engagement teeth are supposed to be sharp points. When they are rounded, it's due to what people call "grinding the gears". Even if they are rounded, it is of no concern.

Re: Newbie with 915

Posted: Sun Oct 08, 2017 12:34 am
by Pablo2
If the sleeve doesn't have these little sharp areas of displaced material, the sleeve may be OK ..
Image

Sometimes using a Dremel on the edges is all that's needed to restore the sleeve to smooth operation.
Image

Re: Newbie with 915

Posted: Sat Oct 14, 2017 10:33 am
by Clatter
OOoo, this is getting good..
The idea of being able to clean up the burrs off the side of the slider teeth is right up my alley!
Thanks for queing me in on the 5 slider, Bruce, they are $950 new! :shock:
I owe you guys a beer at least for sure. :mrgreen:

Got on Pelican, and ordered up the obvious things, like a gasket set and some nuts.
Turns out .004" = .1mm, which is the only shim they sell.
(That's about all I can afford right now... :oops: )

Since it looked like squirrels had need chewing on the mainshaft nut:
Image

Decided to rig up a hoakey way to loosen; see if it was less-than-tight:
Image

Sure enough, it popped right off without grief - way way less than 188 ft.lbs.

Even was able to use a plain ol' puller to the get gears off of the pinion shaft:
Image

All ready to start the sacred Gas Bath ritual when Mom yelled me back into the house..
Image

Big fun.. Loving this stuff..
Thanks again for sharing the wisdom, guys.

Re: Newbie with 915

Posted: Sat Oct 14, 2017 10:58 am
by Clatter
So, kind of at a cross-roads here..

Still have to get it cleaned up, and verify 100%,
But,
So far the bearings look good.

While the initial instinct is to dive in and press the pinion bearings off of the pinion shaft,
That doesn't exactly look like the easiest thing to do:
Image
At least, not without damaging the bearings..
I guess my next move is to go and press 4th gear off, and inspect the '4-point' ball bearing under the cover.

The reason I'm so squeamish, is that there are SIX HUNDRED DOLLARS in just those two bearings right there..! :shock:
Of course, then it makes sense to do the other pinion bearings, and the mainshaft bearings, and..


Peter Zimmerman offers this little ray of hope:
"COMMENT: There was a time when I would do a synchro repair and put the transmission back together. Of course, we had a known user history for at least 90% of the 915s that I repaired, and we knew that pinion shaft and main shaft bearings had an expected life of 150K + miles. Today, the typical 915 has been removed from a car with 3+ owners, unknown mileage and unknown use. Some have come out of wrecked cars, some are sold as cores, and some have found their way to market as a result of a car being upgraded for sporting purposes. If a 915 is apart for repairs, and it’s anything other than a known “virgin” with less than 100K miles, the three pinion shaft and three main shaft bearings should be replaced."


Looking and looking, the main big pinion bearing race in the case is tight in the bore, with no pits or ridges.
The pinion bearing rollers are shiny and smooth..

Is there a measurement, like in some other applications,
Where we insert the pinion shaft in the bore, and measure the lateral play at the end of the shaft?
You know, like a 'wiggle' measurement, that would give an idea of how worn that little sucker actually is..?
:?:

Re: Newbie with 915

Posted: Mon Oct 16, 2017 12:35 pm
by Clatter
Things are looking up..

First of all, I exaggerated on the pinion bearing prices.
The pinion bearing is $374.00 and the 4-point is $119.75.

Looking at these bearings closely, they sure do look nice to my un-trained eye.
They turn smoothly, the rollers are shiny, no streaks or pitting..
Image

Mocked the pinion up with bearing in housing, to measure 'wobble' or lateral play:
Image

Gave me a little more than .040"..
Is this technique even valid here?
Image


Got some good pics of cleaned parts.
I understand how they work now.. :oops:
Image

Until I get a press (tomorrow) it's only the pinion shaft apart so far,
But none of the races had any 'chatter lines' they warn of.
Image


Lastly,
Would this one be a good candidate for the Dremel touch-up vs. replacement?
Image


Thanks and thanks again for your input.

Re: Newbie with 915

Posted: Tue Oct 17, 2017 1:37 am
by Bruce2
Both sliders look to be in great shape. Don't mess with them.