Why are the lower rears bolted to gearbox?

[bert knip]

As I am getting closer to make my 71 europa a roller again, I started wondering why Mr Chapman decided to use the gearbox
as part of the frame.
Is there any reason thinkable for this construction? There can be some movement in the engine and gearbox mount so
It is not a fixed point.
I am thinking of making a conection in the frame, and leaving the gearbox out of the construction.
Ok it will ad little weight, but it will strenghten the chassis.
Also you can make it a roller without having to put gearbox and engine in. And it will make future engine and gearbox repairs more easy.
So please do and don t s
Has anyone done this already?

[jbcollier]

It's simple, light and it works.  Downsides are NVH issues and some rear steer if you do not keep things in good shape and adjustment.  Banks makes a "Twin-Link" system that partly takes the transaxle out of the equation:

https://www.lotus-supplies.com/parts/suspension/rear-corners/twin-link-rear-suspension-system-kit-s1-s2/

I have it on mine, works well.  Wouldn't be too difficult to make up your own if you are good fabricator.  You could also carry on around the transaxle and eliminate the lower mount as well.  Have to be in several pieces otherwise there would be no way to remove the transaxle.

Keeping the wheels up right with the transaxle removed is a little tricky as there is no easy way to contain the rotating and flopping driveshafts.  I would simply build a wheeled dolly to support the rear chassis loop.

[bert knip]

Thank you for your exlanation and the pictures of the Banks part.
I was thinking of a construction under the gearbox,  so that it will be part of the chassis, so there wont be problems getting the engine and gearbox out.
Or am I missing something?

[jbcollier]

There are two links to support on each side: the lower link and a new link to take the load off the driveshaft.

[4129R]

Racing car influence. Simplicity and lightness.

Ditto using the driveshafts as the top suspension links.

[bert knip]

Seen the double links.
But I am thinking of making a bracket going under the gearbox, where the origanal plate meets the gearbox, and not attach to the gearbox.
So then the links are attached to the bracket in the same place where they originaly are, but not bolted to the gearbox.

[jbcollier]

So you'll have the lightly-loaded lower links on the chassis and the highly-loaded uppers still through the halfshafts and transaxle?

[Pfreen]

You could use solid engine and transmission mounts which would make the lower links essentially part of the frame.
The stock mounts are pretty stiff, so I am not sure how much this would increase vibration.
Has anyone used solid mounts?

[bert knip]

Not intending to make connection between lower links and transmission.
I want the links, in the original position (under the gearbox), but want to make a bracket that goes to both sides of the chassis.
Connecting the gearbox direct to the frame looks a bad idea.

[SilverBeast]

Are you going to use something else (instead of the drive shafts) as the top suspension link?

My gut feeling is that if you don't do this, and also mount this to the chassis, you will get more rear suspension geometry changes due to the gearbox moving within its mounts than at present. At the moment the geometry is more than likely most affected by torsional twist of the gearbox. You would have this plus the relative shift of your new bottom mount and the gearbox. I'd also suspect that the weight of the car at the moment compressing the drive shafts into the gear box would also help hold the gearbox more rigidly in place.

As I said it is gut feeling using my "logic". It is not intended as a criticism, more a discussion point. It's one of the reasons I joined this forum (apart from buying a Europa!), to learn about these things and hopefully help others avoid potential mistakes due to misunderstanding. I also accept that I will also be massively wrong on (many!) occasions. Please read this comment with that in mind.

Finally, massive respect and good luck with your build. Can't wait to see the finished product.

[bert knip]

Thank you, I started this item to learn and start a discusion.
I want to know,  is there a good reason to connect the lower links to the gearbox (like I mentioned before it could be the little
movement of the gearbox in the mountings thats the only thing that I can think of)
But when I make a bracket, where the lower link mounts will be in the exact same place, I do not think that the geometry
has changed then.
When the lower links are mounted on the bracket, which is welded to the chassis you will have better, stiffer construction,
Which in my opinion would result in better roadhandling, because the unpredicted movement of the gearbox is playing no role.
I would use the driveshafts as upper, just like in the normal setup.
Hope to learn more, because the construction with the fixed driveshafts seems weird to me also.

[jbcollier]

"because the unpredicted movement of the gearbox is playing no role"

The highly-loaded, upper links (half-shafts) are still anchored to the gearbox therefore gearbox movement will still have an effect.  Given that it now does not affect both links equally, it will induce a new load-related, camber change to the rear wheels.