transmission mounting bolt - 915

[joe_72T]

Hello all,

I have a 1972 911T and I heard a pinging/rattling noise combining from underneath on my drive yesterday. I put her on the lift to have a look. I am missing one mounting bolt and washer. See pics.

Not sure what size I need and dont want to take off the other bolt. Can anyone tell me the exact size of bolt I need?

Thank you in advance!

Joe

[universeman]

PET lists front suspension crossmember bolt as M12 x 1.5 x 85, maybe it's the same size as the rear?

Those smaller bolts in your picture are M8x16

The missing bolt you have is just called "hexagon-head bolt" in the PET, no size given, sorry. Maybe someone else will chime in.

[uwanna]

Tread carefully, there have been many instances of someone cross threading that bolt and ruining the threads (very easy to do). When this occurs, some folks just keep on
torqueing the bolt till all the threads are effectively useless and there is no force holding
the trans mount to the body on one side. The bolt then will probably fall out!
I would recommend removing the remaining bolt (jack under trans) or get a new one and try to test fit in the open hole to see if it will start to thread finger tight.
If the threads are indeed shot, you will need to drill out and Helicoil or Timesert the hole.
By the way, use the original Porsche bolt, not just a common M12 x 1.5 x 85. The
original bolt has a taper at the point to help guide it correctly.
A tip on inserting these big bolts, is to loosen the four small mount nuts so you can wiggle the mount to align the big bolts easier.
Good luck!

[Trackrash]

More info here. Tranny Mount Bolt Size?

[DRACO A5OG]

Make certain it is perfectly aligned and finger thread her in, if there is resistance, try again until she goes in smoothly.

[chrismorse]

Originally Posted by uwanna

Tread carefully, there have been many instances of someone cross threading that bolt and ruining the threads (very easy to do). When this occurs, some folks just keep on
torqueing the bolt till all the threads are effectively useless and there is no force holding
the trans mount to the body on one side. The bolt then will probably fall out!
I would recommend removing the remaining bolt (jack under trans) or get a new one and try to test fit in the open hole to see if it will start to thread finger tight.
If the threads are indeed shot, you will need to drill out and Helicoil or Timesert the hole.
By the way, use the original Porsche bolt, not just a common M12 x 1.5 x 85. The
original bolt has a taper at the point to help guide it correctly.
A tip on inserting these big bolts, is to loosen the four small mount nuts so you can wiggle the mount to align the big bolts easier.
Good luck!

Thanks for this good bit of advice. I am going to R&R the 915 for a rebuild soon.

Regards,
chris

[joe_72T]

Thank you Universeman and others. This is most probably the case. Timeserts will be the way to fix the mount.

Awesome info. Thanks again.

[LM3929]

I have the bolt and maybe a washer you can have for the postage

lorne m.

[juanbenae]

those bolts are sharpened like a mascara pencil and are hard to cross unless you have no sense of feel from the elbow down. when reinstalling loosen all four of the nuts where the carrier mounts to the trans housing and the remaining bolt thru the trans mount while supported gearbox with a floor jack. with everything this sloppy loose you can thread in the missing bolt and retighten everything when the new bolt is finger tight. I believe they are the exact same bolts that secure the motor mounts at the back of the engine. maybe look into part numbers.


and yes, I do keep my mascara pencil sharp

[petercoetzee]

This happened to me, but it was something more sinister. Rust had eaten away at the thread.

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