Xantia with AL4 - Front Subframe

addo · Unread post by **addo** » 20 Dec 2008, 22:54

Part of an ongoing project (

) has seen me print hundreds of pages off the Service.Citroen website, and pore over differences between drivelines/suspension.

One of the more interesting discoveries has been that the AL4 spec subframe is held on by 1/3 less bolts!

All subframes have four trailing edge 12mm bolts through shock rubbers, but most other units also have two forward bolts, up above the lower control arm front pivots. Lacking these two, our AL4 unit instead relies on the engine/gearbox mounting bushes to stabilise its front end floppiness. It makes the condition of motor mounts somewhat more important on this driveline configuration.

Further, it explains why a harsh shift with this 'box, precipitates such a "lurch" - the entire front end is flapping up and down. I'm looking forward to seeing what kind of workaround can be devised.

Hmm...

andmcit · Unread post by **andmcit** » 20 Dec 2008, 23:01

Addo, as nobody else is bothered to ask and in grave danger of showing my
ignorance here, I'll carry on regardless and ask!!

What is that red thing in your avatar? Nail gun or implement of torture?

Andrew

addo · Unread post by **addo** » 21 Dec 2008, 08:08

Yes, a Paslode brand gas-powered nail gun. It's one version of the avatar I use on all sites.

Hopefully, someone may have trodden this path before with the 'box and subframe.

KP · Unread post by KP » 22 Dec 2008, 07:56

Could the front of the subframe not just be drilled to accomobate the two forward bolts then to avoid this as im assuming the other front end panels would be the same as the other xantia's and thus allow this kind of fitment or is it that the suframe on the auto's does not even reach this far?

addo · Unread post by **addo** » 22 Dec 2008, 09:24

On the nearside, the AL4 end housing is physically in the way of where other subframes have an outrigger. Not sure about the offside.

XM's had funny little struts made of tube with flatted ends - like an Alfa 33. I have been pondering a simple fix like this (or does one get silly and start fishmouthing 4130 tubing)?

Regards, Adam.

KP · Unread post by KP » 22 Dec 2008, 09:52

Or just something like liquid metal or a small stitch weld maybe? Wouldn't offer much flex mind...

addo · Unread post by **addo** » 22 Dec 2008, 10:03

You still need a vibration isolator in the juncture. If you hardmounted the subframe to the front rails, you'd get massive ride harshness.

Recurring stresses are a good way to failure test an under-engineered part.

If work ever slacks off (feels that way

) I might put it on the hoist and start mocking up bent bits of coathanger wire...