Porsche transmission mounting

Can the Porsche 930 transmission be hung off the engine/mid plate without any support to the mounting pad? If the engine is mounted at the front and middle on poly bushings,would rear support stays induce any binding or interfere with any natural "harmonics" or motions? I have seen pictures of sand rails with V8s and Porsche gearboxes hung off the back with no support. There were a few Hewlands (DG300,DGB) that did not have any provisions for a tail mount.I do not want to solid mount the engine as I have been told that solid mounting a LSx series of motor induces false knock signals from the vibrations.
What are some thoughts and opinions on this??
 
Dave,
I would think you should be able to do the things you want. I however think that at low speed you may get some shuddering on releasing the clutch at low speed without many revs behind it. At least that is what I heard from a builder of a 40 the other day. His unit is suspended at the rear. I have mine supported at the mid section of the trans. I have a strong frame member alongside the trans, so it makes a good place to mount it.

P1010060-1.jpg


I could have done it at the rear but I have a bracket for the trans selector mounted there. I also plan to run a mount from the engine mounts to the adapter plate to cut down on torque forces. Some DRBs are done that way.
I have several pics of systems that did use a rear mount. I can supply them if you have an interest. I'm no engineer, so one of them can chime in and set us both straight.

Bill
 

Randy V

Moderator-Admin
Staff member
Admin
Lifetime Supporter
My thoughts on the subject are ;

Porsche didn't design that transmission to be hung solely on it's bellhousing, and in particular it wasn't meant to be mounted that way, Inverted and running twice the HP/TQ through it than it was originally designed for.

You can see how I addressed this on my website (link below) for the G50/03 (modified)...
 

Russ Noble

GT40s Supporter
Lifetime Supporter
Dave, my thoughts on it are that mounting loads of the motor/trans on the factory porsche setup tend to put a bending load on the bellhousing face any way. ie the assembly would tend to sag (or open up at the bottom) at that face. Flex here, on an unsupported GT40 application, may well cause the clutch judder that Bill alludes to. Flatchat (Chris Hatfield) makes a nice stiffening bar that goes from the lower bellhousing bolts back up to the engine block each side, there's photos in one of his posts somewhere. Not difficult to do and I think that would stop that judder.

Unless I'm mistaken I think those Hewlands have mounting bosses cast into the tops of the sideplates and many Hewlands are specifically designed to be solid mounted as part of a stressed member.

My trans is hung out the back unsupported, although solid mounted off the rear motor plate. In fact the rear body mounts are tied into the rear of the trans to provide lateral stability for the rear clip, so that will feed extra loads into the unsupported trans.

I think you'll be fine, particularly if you add a pair of Flatchat type braces.
 

Attachments

  • exh lhs 2.jpg
    exh lhs 2.jpg
    168.5 KB · Views: 275
  • Chassis 033.jpg
    Chassis 033.jpg
    35.6 KB · Views: 231
Last edited:
Back
Top