915 Rebuild

[Wally]

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 :

Yanked it out of the car:


Removed the underside cover:

[Wally]

And removed the nose-cone:


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:


After removal of the mid-section of the tranny. This is where 1/2 and 3/4 gears live:

[Wally]

This is what the two gear stacks look like out of the case:




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'
When the new parts have arrived, I will update the build-up again.

Best regards,
Walter

[Wally]

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



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...

[Sandeep]

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

[DORIGTT]

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!

[ricola]

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

[Wally]

Originally Posted by DORIGTT

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!

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?
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'

[Wally]

This is what it looks like when you go parts hunting in 'the right place' :


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

[CLKWRK]

vw dasher maybe?
bry

[wrenchnride247]

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

[CLKWRK]

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

[Bad bug]

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

[Bugat5speed]

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

[Steve C]

Hi

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

Steve