Vibration through steering on acceleration only

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Dormouse
Donor 2022
Posts: 1273
Joined: 15 Apr 2021, 14:32
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Vibration through steering on acceleration only

Post by Dormouse »

Hi All. I haven't been hibernating, just very busy with a roof top solar electric and water heating project on Pint Pot. Our 3008 has been getting an odd steering vibration on acceleration only - it goes away when you lift off and is reduced when on part throttle. It started about 6 months ago and got slightly worse with time. I checked bushes, steering, drive shafts and wheel bearings and could not find anything obvious. I changed front tyres to Winter Tyres and if anything it got slightly worse. Changed back to Summer Tyres recently and it got no better so I had the wheel balance checked at another garage and they found a 10g discrepancy on one wheel. While this improved the situation slightly, it didn't remove it. So I replaced the locking wheel bolts from the front wheels in case these slightly chunkier bolts were a problem, they were not and did not make a difference. I have checked the rear suspension as well as the front a few times now with no obvious issues and the car has just passed it's MOT with no advisories despite telling the garage about my issue. I have checked the discs for run out and cannot find anything.
The worst vibration is at about 50 mph and is gone at 70 mph.
I am heading for repacking the joints in the drive shafts but would appreciate any tips or help before I start. Cheers.
Dormouse
Donor 2022
Posts: 1273
Joined: 15 Apr 2021, 14:32
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Re: Vibration through steering on acceleration only

Post by Dormouse »

Inner and outer front CVs appear ok. Does anyone have any experience of faults with the engine mounts on these 2 litre diesels with an AMT6 gearbox? Had to use a different test road with more straights and longer inclines due to roadworks on my usual one and this threw up that the vibrations subside with each gear changing in auto mode and then immediately come back again when the next gear is fully engaged without moving the throttle. Easing the throttle still reduces the vibration and lifting off removes the vibration.
Second question - would a slightly sticky rear brake caliper/handbrake cable cause this vibration? The car has just passed it's MOT and I can't find any issues but one rear wheel has always been dirtier than the rest with brake dust. The disc in question is ok with no signs of wear and looks no different to the rest, has no excess runout and the pads don't appear to be oddly worn, but sticky brakes can cause odd vibrations and I am trying to find clues before I tear the thing totally apart.
ozvtr
Posts: 205
Joined: 13 Oct 2020, 01:11
x 58

Re: Vibration through steering on acceleration only

Post by ozvtr »

If you can feel it through the steering wheel it's in the front end. If you feel it in your bum, its in the back end. OOPS no pun intended! :oops:

I don't think it's drive shafts, brakes, tyres or bearings. They tend to make constant noises. Front disc problems tend to manifest as pulsing of the brake pedal on application of the brakes.

Bad CV joints don't tend to make noise in a straight line. They typically "clack" when going around corners. Unless they are very worn, you usually don't feel them through the steering wheel.

One thing I can suggest is; pop the bonnet, start the engine, apply the parking brake, put the car in gear and attempt to move the car forward and backward while the parking brake is applied. Look at the engine and see how much it moves on its mounts. Just rock the car backwards and forwards enough to start putting strain on the engine. If the engine mounts are not serviceable, the torque of the engine will cause it to move excessively on the engine mounts. Generally speaking though, worn engine mounts tend to cause a "clunk" on acceleration or deceleration. Not typically a vibration.

You can try the "bounce test" on the front end to test the shock absorbers. However this only tends to show up very worn shocks. It's still possible the shocks are bad but 'pass' the bounce test. Good shocks will dampen out natural vibrations from the suspension geometry that can occur on acceleration and/or deceleration.

Unfortunately it's best to get the car up on a hoist to check the suspension and steering. There are a lot of things it could be, but you will just have to go over them one at a time. IMHO every part of the front end geometry is a suspect! Sorry, that I cant be specific.
Dormouse
Donor 2022
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Joined: 15 Apr 2021, 14:32
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Re: Vibration through steering on acceleration only

Post by Dormouse »

The car is a Hybrid4 so has drive to all wheels at most points during tests. In ZEV (rear drive only) there is no vibrations. In Auto, Sport or 4WD (uses front and rear drive in various combinations) the vibration starts at about 40 mph and is felt through the car body first and, as the speed increases, a shudder through the column appears slightly as the body vibrations reduce. There are less vibrations below 30% power application than above. I am going to take the front undertray completely off to get better access to the transmission and mountings.
Dormouse
Donor 2022
Posts: 1273
Joined: 15 Apr 2021, 14:32
x 271

Re: Vibration through steering on acceleration only

Post by Dormouse »

My gopher ( next door neighbour's son) has been dispatched under the car and has come back with lots of pictures and has been pushing, pulling and levering the bits I can no longer reach. Upshot is that up inside the undertray was dried and crusty grease from what appears to be the nsf inner CV boot area. Closer inspection shows a nick on the very inner edge of the boot so I have ordered a replacement drive shaft as I suspect the inner tripod joint is dry and now wearing. I was going to repack the front shaft joints but I have decided to fit a replacement shaft. Once it is fitted I will report back. Plus any interesting photos of the tripod joint - any wear will be minimal but a worn inner joint can cause vibration. We will see.
Dormouse
Donor 2022
Posts: 1273
Joined: 15 Apr 2021, 14:32
x 271

Re: Vibration through steering on acceleration only

Post by Dormouse »

After a fair period now I finally have some pics to put up of the worn drive shaft inner tripod joint. I acquired a low mileage driveshaft from an identical model to ours and stripped it down and refurbed it at a fraction of the exchange price from Peugeot - the prices for shafts are in another blog on this subject elsewhere.
As Peugeot driveshafts for this model have staked on tripod spider wheel carriers and not circlips, I decided it was better in the long run to to have a shaft ready to put in so the car did not sit idle while the parts were sourced. Plus, I couldn't have done the crawling about myself anyway. I am ok when I am standing at a bench or a ramp.

The garage who has been looking after our cars would not change the driveshaft for us so that set us off on a quest to find a reliable garage that would do the job for us and that threw up an unexpected issue/explanation. The original shaft had a blob of silicone sealer over the cut in the inner CV boot! I don't know exactly where or when this happened but it explains how the joint ended up dry. Silicone sealer does not stick to rubber and the grease just centrifuged out.

Anyway, pictures.
1654258618143.jpg
the refurbed shaft I prepared earlier.

The old shaft
1654258815354.jpg
The small nick that caused all the problems.

The shaft as dismantled showing the lack of grease
1654259076670.jpg
1654259076599.jpg
What a tripod shaft should look like on taking apart
Opera Snapshot_2022-06-03_122139_www.google.com.png
What a tripod sleeve wear pattern should look like
Opera Snapshot_2022-06-03_122709_www.google.com.png
What the wear actually looked like
1654260105863.jpg
1654259076511.jpg
1654260105811.jpg
No wonder I felt a severe vibration!

PS the car is running perfectly now with no vibrations!