Shortened Trailing Arms- shorter driveshaft? And how to measure?

[bugjam1999]

Hi all,

Following on from this thread:

Volvo 240: center rear wheel in arch - the easy way

Tired of having the rear axle not centered in the wheel well? There used to be two different ways of correcting this: 1.) use adjustable torque rods to tilt the axle forward (and messing up the pinion angle at the same time) 2.) section and reweld (=shorten) the trailing arm. Quite some work...

turbobricks.com

About centring the rear wheels in the arch by redrilling the holes in the trailing arm forward by 15mm, does anyone know if it’s possible to use the driveshaft without modification, or does it need shortening as well? If so, how to measure it? I realise it’ll only be the rear section that will need modification, as the front section to the driveshaft support bearing won’t be affected.

One method might be to remove the driveshaft slip joint rubber cover, jack up and support the car at ride height and measure how far engaged the slip joint is, then swap the trailing arms for the shorter ones, reassemble and remeasure how far engaged the slip joint is…

Any suggestions or comments?

Cheers

 

[Stiggy Pop]

I shortened my arms about that much and have no driveshaft issues

 

[Radtap]

Factory drive shaft has a slip joint which will take up any difference.

 

[bugjam1999]

I know there’s a slip joint there- but is there really enough extra play in it to accommodate shorter trailing arms?

Thinking further, if I put it all together and leave the car on jackstands with the rear springs removed, I can jack the axle up to the limit of its travel and see if the slipjoint completely closes up.

Cheers

 

[JohnMc]

I've measured the length in mine a couple of times (getting custom driveshafts done for T5 and CD009 transmissions), and the length barely changes from full droop to ride height. The driveshaft shop wanted the measurements, I guess some cars move more. I didn't measure at full compression since I didn't take the springs out, but it rides modestly low so there's not a lot of up travel left.

And I'd say with 99% confidence that you're not going to have any issues moving the axle 15mm forward. Just unbolt the driveshaft and push it forward. You've probably got at least double that. Probably more.

 

[Stiggy Pop]

I know there’s a slip joint there- but is there really enough extra play in it to accommodate shorter trailing arms?

Thinking further, if I put it all together and leave the car on jackstands with the rear springs removed, I can jack the axle up to the limit of its travel and see if the slipjoint completely closes up.

Cheers

Yes, and that’s exactly what I did to check.