Flipping the ring gear

[bongiorno]

I've head about flipping the ring gear is possible but can't find much information about it.

What needs to be machined in order to get the correct clearance? Also - does this have to be done at a machine shop or carefully done with a grinder?

Thanks in advance for any help or url in the right direction!


Frank

[crustychief]

The ring gear? that would put you in a different direction, like reverse! 911 to 914 conversion? I used to do it to Volkswagen transaxles to turn them into mid engine sand rails. Not sure about the transaxle you want to do it to. I would post the type I.E. 915, 950 etc and the year and I am sure someone will let you in on the good stuff.

[crustychief]

http://www.renegadehybrids.com/
Give these guys a call if no one answers your post.

[GH85Carrera]

5 reverse, 1 forward

[bongiorno]

Sorry - should have been more specific

It's a 915/40 (magnisium case) that I have mated to a Northstar engine with an adaptor from Kennedy engineering used in a mid-engine application (lamborghini Diablo Replica).

[bongiorno]

A couple of pics of my project:

[crustychief]

Very cool! I think renegade is right up your alley then, they do a lot of work for kit cars and such.

[DonNewton]

Holy crap. A northstar in a kit car. . . Kiss your license goodbye.

[herr_oberst]

Don't show this thread to the playa, he'll be drooling over your stroseks for weeks on end.

Seriously, is that tranny beefy enough for norstar muscle?

[1980 911 sc]

I beleive that is a 4 liter Aurora motor. the little sister of the northstar 4.6 liter. the also beleive the hotter 4.6 liter cams (ETC) are interchangable...

[Joe Bob]

If you are a DIY kinda guy, which I assume you are....pull apart a 901/914 trans. It's already oriented in the direction you want to travel.....

I have one apart right now. I can take pics if you like. You don't list your location otherwise you'd have an invite to come by.

[dentist90]

How do you work out the shift linkage in this setup? The shift rod is pointing out the back of the car.

[bongiorno]

Let me answer all your questions - thanks for the complements, this project is a rather large one to take on (been working on the custom frame and such on and off for about 8 years now) but I'm starting to see the light at the end of the tunnel and it will be a big go-kart after I finish the transmission.

4.6 Northstar.
It's a vin 9 295hp 1996 motor stock but I have a chip and custom 1 7/8 main tubes headers - So I'm guessing it's has a little more hp now..

I do want to rebuild/flip the ring gear myself instead of buying one already setup for the following reasons:
- The cost is pretty high to buy a rebuilt/flippged 915.
- I already have the 915
- I enjoy working on my project and love to learn
- I intend on doing another mid engine project in the future.

For the shifter I intend on using a cable system. I know it will be sloppy but I don't think I have another choice.

Questions I have:
I am just pulling the gears out of the transmission now but I'm unsure if the case will have to be machined to flip the ring gear?

Are there any Porsche guys in the Austin, TX area I could tap for help?

I'll be posting more pictures sometime on Monday to ask for recommendations on replacement parts needed. So far I have to say I think I got lucky with this transmission. It looks fairly new inside.

Best Regards - and thanks again!!!!!

Frank

[Black_Hat]

flipping the ring gear is not the hard part.Setting up the rear end after flip is
if its not right it will not last especially with the tq of a V8
take it to a pro

[longhornchris04]

As other's have said, the 915 (EDIT - especially the Mag Cases, they were paired to the smaller engines. There's a reason Porsche went to the Al cased 915s with the SC motors) wasn't designed to handle that kind of torque w/o some significant mods - not including the ring flip. 911s have never been about low-end torque.

Read up on racing mods for the 915 - specifically case reinforcement and cooling. I'd hate to hear that your hard work disappeared when your transmission self destructed.

[bongiorno]

What does renegadehybrids.com do to their transmissions that make it take the HP? I'm not looking to make a race car. It will be a fast, show car for the road.

I'm not opposed to making some of the changes myself and then either going to a Porsche shop or attempting to do it myself (with the right tools of course).

I turned the ring gear 180 degrees this weekend but it's rubbing against the case. I assume something has to be changed and/or ground down?

Thanks,
Frank

[midlife]

Wevo makes a side shift for a 915.


It's not cheap, but would save the hassle of developing a cable shift system.

They also have the mods to beef up 915s.

[bongiorno]

Can anyone give me some advice/link ideas on what is done to flip the ring gear?

I turned the ring gear 180 degrees this weekend but it's rubbing against the case. I assume something has to be changed and/or ground down?

Best Regards,
Frank

[longhornchris04]

Frank - I can't help with the ring gear flip, but I can list off the big-issue items to help with the torque.

- differental housing reinforcement plate - strengthens the case at the point of largest load
- bearing retainer plate - reinforces the bearings
- oil cooling (several components) - general protection... probably the first thing I would do if I were you. Being behind the engine is going to add to the heat loading (remember 915s ran infront of the engine in the cool air)

You may want to post in the 914 forum. A lot of people have done 914 to 914-6 running 915s and have to do the ring gear flip.

Good luck.

[stevemfr]

Aside from the mods mentioned above, the 915/40 will have a 7.31 R&P which is much more torque-fragile than the 8.31 used in later 915's.

Do a search on '915, rebuilding' and '3.6 conversion, 915' or similar.

Neat project!