Hi all, I have a lmc motorhome on a 1990 ducato base with the su8 2.5 diesel transverse mounted. It has a odd wheel wobble which can be felt through the steering wheel strongest and seems worse on certain cambers and normally comes in at 50-60mph but can be slow speed in certain situations too (up or downhill) , at which point everyone can feel it violently through the floorpan never mind the wheel.
You can actually feel it through the passenger seat on a bad day and of course its getting worse with time. Its not regular though, on certain roads or cambers etc it doesnt occur at all regardless of speed. We had a advisory on the controle technique (french mot) that it had minor play in the front suspension arms somewhere, but its not specific and the tester couldnt say exactly where it was, and he's a bit keen to write stuff down to make the paperwork look better sometimes so not sure.
our local geometry/tyres/exhaust place took a look and said there was nothing wrong with it, and the local proper garage wont work on it because they say its too big for their ramps, the mrs wants to take the family away next weekend, so Ive rolled up my sleeves and am giving it a looking at.

Ive had the front of the mh up on axle stands, and with a largish lever (12inch or so) I can work the bushes around on the end eye of the lower suspension arm where it attaches to the chassis, but I cant feel any actual free play at this point. So I'd guess I'm just feeling compliance/distortion in the bushes themselves?

Ditto for the arm which runs forward and forms the front part of the lower triangle, the bush at the chassis end will move if levered but no clunk clunk free play. The steering and lower balljoints all feel ok, no play in the wheelbearings either. No play can be felt in the wheel itself top to bottom, nor front to back, only the start of a slightly squidgy feeling which Id again assume was the rubber bushes? Is it normal for them to have some give when levered about, or should they be absolutely solid under my puny force compared to what they will see in service?
Im a bit lacking in experience at how it feels when its good or not.

Ive just changed all the engine and lower gearbox mount as they looked perished, and it hasnt made a blind bit of difference although drive take up now is a bit smoother, so not a total loss.In need of new ideas what to check and if those bushes are ok now...

You need to start with the basics- wheel balance and alignment. Perhaps fit your spare wheel , road test, if no difference, swap it to another position. Some tyre defects will only be apparent when warm. Check for bulges in the sidewalls of the tyres.

Just wondering if it might be slight wear in the driveshaft(s) though this would be more an explanation for the low speed vibration (knocking?) you are getting.

As Arkk says it's worth changing/balencing wheels first, though you may be able to check for play in the joints (there shouldn't be any!) without any dismantling

How many miles has it done?
The rubber bushes will have a certain amount of give in them when levered, but only slight movement should be noticeable.
The first thing I would try is find yourself a large empty car park maybe Tesco at night.
In first gear go slowly on full lock first one way then the other; is there any knocking or the sensation of the front of the vehicle going up and down? This would suggest driveshaft problem. Knocking is outer joint and the up and down sensation is inner joint.
If that’s O.K try jacking up the front wheels and spin them by hand and just gently rest the palm of your hand on the tread, can you feel any undulation this would suggest a damaged tyre maybe the tread is twisted; this is best done after a run when the tyre is warm.
Good luck.

Theres 120,000 miles on it. There is no clicking at the extremes of steering indicating outer halfshaft spider wear on full lock, Ive had plenty of shennanigans like that with my master vans over the years to know the noise to listen for. Ive already swapped wheels round and found no change but thanks for the suggestions.

However, Ive been under it all today fitting a new cambelt and other bits n bobs of service parts and while it was up on ramps to get the leverage to get the crankshaft pulley nut undone, I got chance to give it a better looking at.
This is where it gets expensive I suspect, the inner halfshaft end where it goes into the diff has noticable play and you can wiggle the shaft inside end around, and instead of seeing play between the stub which enters the box and the shaft itself which would indicate the inner halfshaft spider is knackered, you see the play between the box and the stub. so Id guess the diff output shaft bearings are in a bad way, or the sliding fit between the halfshaft carriers and the yoke stub is ruined.
Id guess thats the source of all the horrid shaking and vibration we can feel through the floor and wheel. At least I have a culprit now.

Anyone know if you can strip the diff without taking the transaxle out the van?

On my Talbot Express (same base as yours) I once had the nearside driveshaft partially come out of the box causing much the same symptons as you've got.

As you may know the driveshaft is located in the diff output by way of a circlip round the shaft engaging in a groove in the output housing, in my case this had sprung out of the groove (I replaced it with a suitably sized keyring as was recommended)

From memory there should be hardly any clearance between yoke and box (in fact the recommended way of getting the shaft out is to use a flat chisel to prise it out, which gives some idea of what the clearance should be) so if there is a lot on your van it might be worth checking if this circlip has given up before taking the box off

Hi thanks for the input its all good, I had another look at it last night while I was changing exhaust mounts (another job off the list!) and there is about 7mm of clearance between the heads of the flange plate on the diff and the stub axle main body.
The clearance is even both sides and about right for running clearance, so sadly its not this (would have been nice though). I think I actually have a new one of those circlips in a inside pocket in my wallet after years of needing one at the wrong moment

However the deal breaker is that one side there is a little play, and the other side is terrible and the more I play with it the more terrible it feels, so it has to be the differential carrier bearings dead on one side. I think I can drop the van onto axle stands, take off the bottom suspension arm from the chassis eye end both sides and undo the forward braces and swing out the hub assemblies far enough to take the shafts out the diff without having to get into undoing them from the hub. Then hopefully the diff assembly can be stripped in place.
Its also had the job done before as the diff case is sealed with orange hermatite gasket compound, so I hope its just a facet of high mileage and always being loaded to need diff bearings twice in a working lifetime, but wont know until its out and on the workbench under good light...

Ive found the bearings online at a german supplier for 48e a side, although Im going to extract them and take them to a bearing factor as I suspect they will be just standard taper roller bearings and a off the shelf piece so should work out even cheaper.

Im just glad I noticed it before I was sweeping the diff assembly up into a bucket at the side of the road. Finding bad problems in the workshop and having to spend time fixing them, not the end of the world and I can work through them at my own pace. Finding problems at the side of the road with family inside getting stressed and having to deal with some dodgy garage very bad!

Its going to drive like a new van after all this!

MrFluffy said:

I think I can drop the van onto axle stands, take off the bottom suspension arm from the chassis eye end both sides and undo the forward braces and swing out the hub assemblies far enough to take the shafts out the diff without having to get into undoing them from the hub.

Click to expand...

What I didn't mention in my last post was that in my haste to lever the shaft back in place (it happened 60 miles from home) with a crowbar, or something equally unsuitable, I put a split in the inner boot

I can't now remember exactly what I had to undo, but I did get the shaft right out of the box to replace the boot without having to dismantle it from the hub, so it can be done.

Thanks, Ive just verified that for the long shaft because I removed the lower suspension arm and undid the forward tie rod as above and I could *just* get the longer of the halfshaft's clear of the diff. Its hanging out the way supported by a strop for now

Ive taken off the oil seal cover plate on the diff itself, and it looks a lot like the cover forms the surface maintaining the taper roller outer in place and setting the bearing preload. If so, I cant think of any reason not to shim it in situ so it has the correct amount of radial play on the carrier bearings rather than taking it right off...

Now its off, the cv on the inner end of the shaft feels knackered too, maybe thats whats pounded the bearing out of clearance. So Im going to end up having to undo that halfshaft nut anyway to replace it

Would any kind soul here know the torque required to turn the diff assembly when the carrier bearings are preloaded correctly?

I know the secondary shaft in the gearbox will add some drag and mess the measurement up, but I'd like to at least make a effort to get it right.

Ive ordered a manual, but Im waiting for it to arrive in international post and Im itching to get this sorted now.