what is this part called?

[CBA]

Whats this?

Also, has anyone got a diagram of 340 Brake circuit, the whole thing as a jpeg. please?

I will post some pics of my new purchase shortly.

[classicswede]

Is there something other than the torque arm we are supposed to be looking at?

[CBA]

the bush on the body-end of the torque arm.
I need one, no.. two. Where can I get one, or what fits from e.g. euro car parts/carlines stock.

[Ride_on]

No substitute at the moment AFAIK other than make your own.

http://www.volvo300mania.com/forum-uk/v ... ar#p154733

[CBA]

my local car shop has a parts bin, I can get stuff welded together cheaply too ....

is it just unbolted or is it going to go whack on me etc?

car shop might have just the ticket for the actual bush. lots of 80's bits...I'll repair the rod if push comes to shove... I have such rubber-making knowledge. I knew the day would come... Car-part apocalypse!

Just how to get it off?

[Ride_on]

Hard to tell from the photo, but if one end is loose it has already gone. All it does is keep the axle level as the suspension goes up and down, as the rear camber is built into the axle it must not rotate. Loose or incorrectly adjusted it will make the rear wheel toe-in more which is a bit dodgy and makes it a bit more tail happy and unpredictable. Puddles used to nearly make my car spin when mine was incorrectly adjusted.

Cut the end off an appropriate amount and weld on a long threaded nut, then stick in a rose joint to maintain the original length. Adjust as per Haynes or Volvo manuals.

[CBA]

I'll see what I can do then, still looking for a scrap part though.

[mac]

Try Superflex universal section - probably something there.

http://www.superflex.co.uk/categories.php?cat=73

Mac.

[CBA]

just have to get the damn thing off to measure up, I may have the resources after all.

how will it drive minus torque rod?

[mac]

Not well!

The torque arm is there to control the rotational movement of the axle around its own axis.

The 300 rear axle has negative camber built in a therefore any "fore/aft" rotation will change this leading to varying toe in/toe out. (not that it could, but if the axle rotated through 90deg the camber would become toe in/out).

Under acceleration the axle will rotate backwards giving toe out (yes I know that the only drive forces on the axle are transmitted by wheel bearing inertia) and hence inherrent oversteer. Braking will induce toe in and under steer. And before anybody says "axle restrained by springs" the springs will 'S' whip.

Mac.

[Chris_C]

Under acceleration the axle will rotate backwards giving toe out (yes I know that the only drive forces on the axle are transmitted by wheel bearing inertia) and hence inherrent oversteer. Braking will induce toe in and under steer. And before anybody says "axle restrained by springs" the springs will 'S' whip.

It rotates forwards, towards the front of the car surely?

Anyone who doesn't believe this happens (I'm sure the drifty boys will comfirm too) if you ever have the back of the car feeling like it is "punching" this is the axle winding up and unwinding on the springs. I get it a *lot* when launching, as the single bar is not enough whenever the grip is reduced, be that by more power or more rain. It's a very very violent punch, between 1 and 2Hz, I think I have a video of it somewhere. The other thing you might get when launching (this is more common in high grip situations) is having to dial on "opposite lock" without the back end sliding, the axle rotates around the single asymmetric link due to the wind up, and straightens out as the acceleration is reduced.

Another really good example is watching the car chase in Bullitt, you can watch the axle wind up and unwind continually on the side shots.

Leaf springs are not a locating rod, no matter what American manufactures, Volvo and Ford will have you believe.

In short, no, don't drive without it.

[trabitom99]

Is that the thing more commonly known as "anti tramp bars"?

Cheers

Tom

[Chris_C]

Correct

[mac]

Now you've got me thinking Chris, with a conventional rear drive the axle will rotate backwards of course (opposite and equal etc.) - think dragster picking front up, and biker doing wheelies. But where the axle doesn't actually provide the drive path ...........hummn..........will wheel bearing inertia give us "equal and opposite" (as I have blindly assumed) or will the axle be "dragged round" following wheel rotation?


Durrr...my brane herts....


However - wee all agree, the torque rod is there for a purpose, so don't drive without it.


Old and confused - Mac.

[Ride_on]

The axle has no significant rotational reaction IMO in the Dedion design. The torque is generated by the diff and the wheels are driven by that. The axle is pushed forwards (not unsurprisingly) into the car against the reaction of the road the wheels. The car front end lift is mainly pushed up by the diff and engine (360) mounts. Actually I forgot that, that was another force on the 340 gearbox mounts to damage propshafts. The axle will follow the cars rotation of course, and the rear spring compress due to the diff torque.

I think therefore that it is not an anti-tramp bar, but it does help transfer some of the forward force from the axle to the car (unevenly). It is a rear radius arm, or track control arm.

As to harmonics on take up, I can only imagine it is due to spring compression, radius arm bushes and loose drive against higher levels of peak grip. I don't remember ever having a problem with it in any of my cars but that would have been 10 years ago and none where tuned.

As we know, such bushes are not available and replacement is not common place. Rose joints for everyone, and maybe a 2nd arm on the other side.