G50/915 Gearbox Questions

[Captain Ahab Jr]

I hope you can answer a few questions I have on the 915 and G50 5-speed gearboxes

Maybe someone has both types lying around their workshop and can give me the measurement from the centre of the output shaft to the engine mounting face for both boxes.
A picture of the two boxes side by side would be a great help also.

I think it's an easy mod to run the G50 inverted for a mid-engined installation but is the 915 as easy to do or is it better to flip the crown wheel?

When people talk of a shortened G50 bell housing how much shorter is that compared to an unmodified G50 box?

What does a G50 and 915 box weigh and what upper BHP/Torque can each box take before frequent rebuilds are required?

[RWebb]

I would plug both terms into the search box and get the comments and data posted already.

Be aware that wts. vary depending on year for both; that the G50-can be lightened by deleting some luxo-clutch items; that the Tech Spec. books give accurate wts. for the whole shootin' match incl starter.

915s have definitely been run inverted - I've seen a few but have never tried it, so dunno how hard it was. It does sound like you will be dwelling in Fab-Land for a while anyway, so...

and... you can add strength to a 915 (increasing the torque-taking ability) at a small cost in wt.

post your appl. and you can get some more targeted answers

if it for racing then what track types? & what RULES!?

if for street, then do not miss MRMs comments on why to avoid the G50

[Matt Monson]

As has been said we need more information about you. Renegade Hybrids puts 400chp against 915's all the time in 911's but it's not something I really think is a good idea. But if you've got some kit car that's 1000lbs lighter than a 911 then that's a different story. Give us the whole picture and we'll help the best we can.

[greg79s]

Remember the G50 will add alot of weight to your car.

[Captain Ahab Jr]

Sorry guys you are quite right, I haven't given you enough info. and should have used the search button.

I would like to build a full tubular space frame chassis under a very stock looking 911 narrow bodied car with a mid-mounted twin turbo engine (450ish bhp, not sure what that would be in torque), total car weight max. 1700-1800lbs.

Imagine a 917, 908, 935 inspired car with a stock silouette that looks like it was built by the Porsche motorsport department as a road car homologated for a still born racing championship back in the 70's. That about the best descrpition I can think as it doesn't fit into any of the more conventional recreation boxes.

The car would not be used for racing, so no rules to worry about but would be used on the road and for road circuit track days running on slicks. It will get a bit more abuse than a purely street driven car and a lot less than a race car.

I am looking at ways to move the engine as close to the rear wheel centreline as possible so I don't end up with my nose pressed against the inside of the windscreen.

At the moment the project only exsists as a CAD model so I can check I am not going down a blind alley with a mid-mounted installation and come up with designs for the other major challenges involved.

A few key dimensions such as the distance from the centre of the output shaft to the engine mounting face for the a suitable gearbox will give me an idea of what other mods. I will need to do to make it work.

I am also looking at other modifications to the driveshafts and bodywork to help with the seating position.

Hope this helps and please ask away if I haven't given enough detail.

Many Thanks,

Stephen

[RWebb]

the issue is torque for the trans. - not hp so you really need to nail that down

at a guess, you may be ok with a strengthened 915 - the Mg cased ones are lighter than the later Al cased ones

let's ignore the turbos as they will not be a huge contributor to torque (for most hotrodders) and focus on the displacement of the motor - P AG used the 915 up thru the 3.2L motors so that is one starting point...

what you really need to know is the distance from the stub axles to the mounting face with the engine for a variety of trannys...

a 2nd issue is what angle can you run the axles at - we know that P AG ran them at an angle, so again as a starting point, I'd imagine that you could use that same angle

if you're lucky, Grady will explain exactly how do it (just like he did way back when)

if unlucky, you will be in dream land for a while...