915 Rebuild
 

Last year, the 915 5-speed in my 1303 with the 2,4 TIV performed excellent, but for the synchronisation of the trans itself. Its a mag-cased 915/40 from '76 with a 8/31 differential.
Shifting up and down to 2nd and 3rd could only be performed with a little time-lag or it protested by grinding.. :(
This was not funny at the track and seriously annoying.

So, for this year I wanted to have the problem dealt with.
That meant either buying another - better - 915 tranny, having some-one rebuild mine or rebuilding this one myself.
Since another used 915 can usually not be tested in the car it came from, that would always be an (expensive) gamble.
Buying a rebuild one is also expensive: I think you're looking at 1.500 - 2.000 euros...and so is having a rebuild done by a good shop.

So, despite my deeply seated resentment of opening a tranny, I have just done that :o :

Yanked it out of the car:
http://www.keversite.nl/fotoalbum/fotos/28800.jpg

Removed the underside cover:
http://www.keversite.nl/fotoalbum/fotos/28846.jpg

And removed the nose-cone:
http://www.keversite.nl/fotoalbum/fotos/28848.jpg

Now I needed to shift two gears in at once, so both the big nuts could be loosenend. Then I removed 5th an dreverse gears and shift rods:
http://www.keversite.nl/fotoalbum/fotos/28982.jpg

After removal of the mid-section of the tranny. This is where 1/2 and 3/4 gears live:
http://www.keversite.nl/fotoalbum/fotos/28997.jpg

This is what the two gear stacks look like out of the case:
http://www.keversite.nl/fotoalbum/fotos/29014.jpg

http://www.keversite.nl/fotoalbum/fotos/29015.jpg

I have found out that all synchros (and probably the dog-teeth) have been replaced not too long ago(!), but that both gear-sliders ($$) are seriously worn. Also the dog-teeth of 2nd seems to have a liitle bit too much rounded teeth, so this will be replaced as well together with 3rd synchro because of markings on the outside and 1st gear brake-band.

Its amazing, but I have been almost cured of 'tranny-fear' :D
When the new parts have arrived, I will update the build-up again.

Best regards,
Walter

Forgot to mention the guilty party: Worn slider 1/2:

http://www.keversite.nl/fotoalbum/fotos/29075.jpg

These shiny bands should have a flat surface. The top one is most out of focus, but you can still see its clearly 'dented' in the middle... :(

Thanks for the pics Wally ... really cool looking at the inside of the 915. I will be making the upgrade from the 901 to the 915 later this year. :agree:

Sandeep

Once you're done, you WILL let us know if that dreaded shift/grunch is gone and that once and for all that the 915 gearbox is not the bane of conversion existance right?!?!

I really don't want to spend the extra dosh for the G50 as long as I can get some smooth shifting (I'm not drag racing, just autocross/time trials and open track events) reliability and power-handling capabilities.

Keep up the good work!

The 915 just doesn't like to be shifted quickly.. I had mine fully rebuilt too. All down to Porsche's design of synchro.

Nice job Wally, I helped with the rebuild on mine and I still don't think I would tackle it on my own!

Rich

For that purpose, it would be excellent. Russel does dragrace with a 915 in his 450 hp IRS bug, so even that would be no problem.

Personally I think with all the right bushings in your shift-rod couplings and the factory short shift kit, these boxes can be made to shift very quickly. At least quickly enough for my taste/purpose I'am sure.
Ever asked about any G50 parts prices? :eek:
I choose this 915 tranny very carefully (weight, CV-size, gearing, cost) and after much thought about the subject ;)

I will put a lot of new parts in it, but not everything ($$). Also because I'am not sure if it would make a noticeble difference if all wear parts would be new.

Thanks for the moral support; i will probably be needing it when I put everything back 'in umgekehrter Reihefolge' :D

This is what it looks like when you go parts hunting in 'the right place' :cool: :
http://www.keversite.nl/fotoalbum/fotos/29648.jpg

"What the heck is that? Hey, its got Posche wheels, but it doesn't look like a P....."

vw dasher maybe?
bry

Thats one nice shop (the cars are not bad either :laugh: ). I think that non- porsche is a VW 412. Those came with type IV motors!

yup its a 412, heres a body shot of one
Bry

Wally is that your orange 411. What type of porsche rimbs are those are they E.T. 52.

Bus T3-clutch with Porsche 915-gearbox
 

Hi Wally,

please send me an email. Have lost your address. Have the "guidance tubes" (hope it´s the right word) for the Bus T3 t.o.b. for usage on 915-gearbox finnished. Can send you pictures if you like.

Bugat5speed
info@bugat5speed.de

Hi

Nice work. Do the 915s need special jigs like VWs to set them up again?

Steve

Nice job Walter.

No need to be affraid for that lovely piece of technique inside the tranny.
If you can build type 4's like you do, this will turn out the right way too. ;)

For those who do not know Walters 412S, here it is:

http://www.keversite.nl/fotoalbum/fotos/24231.jpg

Sorry @all. Lost track of this thread when update emails weren't send anymore.

@ Luuk: thanks!

Martin, will send you an email. Good to know there are options. I'am curious what you have thought-up about the clutch cable routing.

@ Steve: no special jigs are required IF you keep the shifting forks intact! I managed to remove them without loosening the fork bolts on the shift rods :D
Loosening the big nuts on top of the gear stacks requires some home made solutions, but nothing fancy (luckily).
It does look easier than working on a 901/914 :D

@ badbug: rims are 7Jx17 ET50 and 8,5Jx17 ET52

Most new parts are now in. Just waiting on one last part, which should be underway :)

Thanks,
Walter

Wally, what is the outcome of your rebuild? I'm about to start my 915 rebuild with possible gearing changes also $$$:eek: .

It worked excellent! I just wished I had exchanged the slider of 1/2 as well, as that is the only part I didn't buy new and its only the only gear shift (towards 2) that needs a little too much effort sometimes ...
I will very probably replace that slider when the engine is updated to the 2,7 :D

Thanks Wally, I hope to have mine rebuilt, and geared for the best power and acceleration with a 2.5 EFI type IV :D . With Jake's help, I shouldn't have any problems.

Question, in replacing the syncros and sliders, was it much to it? I to have the "I'm going to mess it up frear thing:o" I know I will need a trans repairman to set the gear mesh for the ring and pinion when I get the GT ATB diff. How about the linkages internally, was ther much to re-set them?

Be carefull what you read on the inetrnet, as my above 'conclusion' was wrong!
The dented part in the middle is supposed to be there....:o

The synchros itself are difficult to get off and on. Lots of force and plyer-force needed iirc. Not fun; possible yes, maybe, just..
I didn't set linkages as I didn't loosen them, but I should have resetted it. Also here: you need to know what your doing. I had to open the tranny once more because of my inexperience...

Tools
 

Walter, did you use any special tools? Press? indicators?

No, not really, just an air socket/wrench (sp?) for removal of the top two nuts (41 and 36mm IIRC) of the gear stacks is very recommended as is an old clutch disk to bold into your workbench. Of course things like a good gear puller, of which I modded the fingers a bit, is without saying.
The special 915 jig to set linkages inside is recommended too. Pelican makes a replica in hard plastic, very cheap btw!
I am sure to have forgotten things, but this is just from the top of my head.

Your new throw out bearing
 

Walter, concerning the I believe a Saab hydrualic throw out bearing that you modded to your G-50 setup. Do you believe this mod can be done to a 915 trans? Before I go any further in my 915 project, I'd like to know how I am going to address the clutch apply issue. I just noted your last dyno test, congrats.

1) I didn't use the Saab TO bearing in the end, but a Ford Mondeo (iirc) model as it was smaller.
2) AFAIK, room inside the 915 bellhousing is probably too small even for the smaller Ford TO bearing...

Hi Walter, I'd like to re-visit the hyd throw out bearning again. So here goes, I am comparing your end results of shorting the bell housing area to basicly match the 915.

Since you did that, would the inside clearences pretty much be the same as the 915?

I really need to consider your method for your G-50 application in the 915. Because of the maching of the bellhousing. Where did you get the throw out bearning?

Hello,

I'am afraid I can't answer your questions as i don't have the 915 anymore and the G50 is in the car so I can't 'have a look' let alone make a comparison...
In my remark 2) above here I think I already gave my opinion on your second question fwiw.

As for the TO bearing, I just bought a nice looking one on ebay ;)

sorry,
Walter