Rear suspension overhaul

[Volvoluke]

Heres the update on my rear suspension overhaul. I hope some find this helpful.

Fyi- this was all prompted by A. A leaking shock absorber. B. The rear end sinking when loaded accompanied by a vibration while pulling away.

The work itself- shock absorbers were a pice of cake to change. The springs where harder work ... a bit of advice, if your going to do this get some replacement top studs and nuts. They were so corroded it was ridiculous this made the job so much harder. None of the rubber mountings were replaced in the process. If it wasn't for the corrosion the whole project would have been easy thanks to a professional spring compressor I borrowed from a neighbor. Doing it with the cheap diy hobbies you can by from screwfix etc cannot be fun!

The springs were replaced with kyb hd springs and the absorbers with kyb gas filled shocks.

The results- not amazing to be honest... although the back end now sits a little higher, once loaded up and or towing a trailer etc the back end still compresses alot. It's not as bad as it was but it's not great.
The vibration is now gone under normal driving conditions but persists when loaded unfortunately especially on hill starts.

Next- I'm wondering if the vibration continues due to either-
1. Not replacing the spring rubber mounts- considering replacing.
2. The springs not being long enough they were shorter than the originals... I'm considering a spacer (available from skandix)..
3. Transmission mount failure
4. Faulty u joints on the drive shaft

[360beast]

The vibration will be the propshaft bearing in the middle of the prop I believe, I need to change mine as it is vibrating.

[Volvoluke]

Originally Posted by 360beast

The vibration will be the propshaft bearing in the middle of the prop I believe, I need to change mine as it is vibrating.

Ah yes, I overlooked that one. I replaced that on my other 940 due to it vibrating only difference was there was obvious movement in the propshaft... dont seem to have that with this car. Probably the only way to be sure would be to replace everything 🤣

The vibrating only began when the old shocks started leaking. I wonder if you can get old shocks refurbished?? The originals seem so much more substantial than the kyb replacements

[griston64]

Did exactly the same job on my 940 at the weekend. I bought the studs along with all new bolts before I started Lucky I did as my nuts ( ooh err ) were also welded with corrosion to the studs.

No need for spring compressors though just pull the trailing arm down after undoing the top nut

Lower rubber spring mounts are no longer available but i had a spare set from a breaker that i soaked in warm water for a week before cleaning thoroughly

[Laird Scooby]

Originally Posted by Volvoluke

Ah yes, I overlooked that one. I replaced that on my other 940 due to it vibrating only difference was there was obvious movement in the propshaft... dont seem to have that with this car. Probably the only way to be sure would be to replace everything 🤣

The vibrating only began when the old shocks started leaking. I wonder if you can get old shocks refurbished?? The originals seem so much more substantial than the kyb replacements

Like Mark said, you don't need a spring compressor on the rear springs , just lower the axle enough and put the new spring in place.

The reason the old springs were a lot longer is they had a lot more travel because they are soft - this extra travel pumps up the old dampers that are Nivomats/Nivos that never worked even when new as they are meant to be self-leveling - they only restore the ride height to "within 30mm of standard" which isn't self-leveling. The bit in quotes is either word for word from their sales blurb at the time or as close as makes no difference. Hence they admitted they did not work for the purose they were sold.

You have a much better set up now and as Luke has suggested, you need to check/renew your prop centre bearing as it will allow the front of the propshaft to droop then when the back end is compressed, the nose of the diff also droops and this causes an imbalance in the UJ near the diff nose in the prop because it's at a weird, contorted angle.

Might also be worth checking the various bushes around the axle and trailing arms, any wear in those will exacerbate the vibration.

[360beast]

I forgot to say the arms that go from the A frame to the axle and bolt to it where the diff is the bushes by the diff can go soft and allow the axle to twist under acceleration.

[Volvoluke]

Thanks for the replies looks like a centre bearing change again it is!

Note on the spring compressor thing- I couldn't find anyway around this. My rear left jacking point is rotten so I had to support the car via the axle.

[360beast]

Originally Posted by Volvoluke

Thanks for the replies looks like a centre bearing change again it is!

Note on the spring compressor thing- I couldn't find anyway around this. My rear left jacking point is rotten so I had to support the car via the axle.

Someone really should make those!

[Laird Scooby]

Originally Posted by Volvoluke

Thanks for the replies looks like a centre bearing change again it is!

Note on the spring compressor thing- I couldn't find anyway around this. My rear left jacking point is rotten so I had to support the car via the axle.

There should be a section of chassis reinforced further in from the sills that you could use an axle stand on - that's what i used when i did mine as the jacking points are bent to hell and back again, courtesy i believe of the previous owner who lived on a steep hill and i think he used the wheel changing jack to lift the car up.

Also the point where the trailing arm is attached to the chassis is i believe reinforced, axle stand on that chassis section while you lower the axle to swap the spring, job done.

Somewhere there is a diagram/photo with these reinforced areas shown, think it's in the Haynes Book of Fantasy (HBoF) but might also be in the Volvo handbook.

Until you get your jacking points sorted out, i'd have a look and see if you can find that photo/diagram and familiarise yourself with those points so you can do things a bit more safely. Even after that i'd be inclined to use the reinforced areas.