I agree this company is very highly recommended he has done some excellent work for us and friends of mine.
Urgent help / advice needed please from experienced mechanics (1 Viewer)
- Thread starter Parapilot
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Silver-Fox
LIFE MEMBER
Just had another look at the film.
Unless your box and engine is moving a lot on its mounts I think the issue is the end float in the axle/diff.
Just a thought did the fit the new diff with new bearings and washers?
Hope it’s sorted soon
Unless your box and engine is moving a lot on its mounts I think the issue is the end float in the axle/diff.
Just a thought did the fit the new diff with new bearings and washers?
Hope it’s sorted soon
seems , most oppinions are coming round to what i said at the beginning, ok there might be something in the gearbox and converters and stuff but the fact remains that diff is not right, its got about half a turn without the vehical moving, just think of the slack there is when easering off or accelerating, im very surprised it hasnt give way.
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Bigger / lower ratio diffs have more rotational slack. Pinion to crown engagement isn't ever the cause - if it was the diff would whine and/or be very short-lived. That leaves the planet wheels & bearings and half-shaft splines. Excess slack can cause a 'clonk' on take-up and the transition to overrun but that's all. Salisbury 4- & 8- HA axles (for example) are known for excessive slack and have been used in everything from dumpers to sportscars without issue. Apart from the rather unsophisticated clonk.
OP
OP
Parapilot
Free Member
Thanks for all the feedback, advice and opinions so far. It all helps as this problem has been driving me mad for the past year !
Clearly from the video there is a major problem and it beggars belief how so many 'professionals' have stripped, tested or replaced everything including diff, prop, gearbox etc. - but without curing or even improving anything.
I will try sending the video to the garages referred to (problem is that many do not have facilities for a vehicle this size), and speak with Truck Transmissions again - as I will need to give them an opportunity to rectify any fault before taking it to yet another different workshop and paying again for the same work to be repeated .....
Can't think what else to do at this stage.
Clearly from the video there is a major problem and it beggars belief how so many 'professionals' have stripped, tested or replaced everything including diff, prop, gearbox etc. - but without curing or even improving anything.
I will try sending the video to the garages referred to (problem is that many do not have facilities for a vehicle this size), and speak with Truck Transmissions again - as I will need to give them an opportunity to rectify any fault before taking it to yet another different workshop and paying again for the same work to be repeated .....
Can't think what else to do at this stage.
OP
OP
Parapilot
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Yes. I know this because of the delays after the diff finally arrived. Bearings on original diff were a heat / interference fit so could not be re-used. New bearings had to come from Germany.
Thanks for the thought though.
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Silver-Fox
LIFE MEMBER
If it were mine I would get new bearings ordered along with seals.
Pull the diff out yet again and do a forensic inspection of the diff housing.
I’d also check the axle is square to the chassis.
Do you get a weird wear pattern on the rear tyres? This would highlight any out of alignment.
Again if the fitter doesn’t follow assembly to the letter you will have issues if all else is good.
Have a look on YouTube for re assembling diffs it’s an eye opener.
Ohh just had a thought do you know anyone that runs top fuel dragster as they know what they are doing with diffs.
I think they use 12 bolt fords?
Pull the diff out yet again and do a forensic inspection of the diff housing.
I’d also check the axle is square to the chassis.
Do you get a weird wear pattern on the rear tyres? This would highlight any out of alignment.
Again if the fitter doesn’t follow assembly to the letter you will have issues if all else is good.
Have a look on YouTube for re assembling diffs it’s an eye opener.
Ohh just had a thought do you know anyone that runs top fuel dragster as they know what they are doing with diffs.
I think they use 12 bolt fords?
OP
OP
Parapilot
Free Member
I hear you .... but ..... Truck Transmissions charge labour £450 to remove and refit diff. Bearings and seals aren't cheap. That would be a grand for another fishing expedition when it is supposedly all new now. (Plus all the time and hassle of 120 mile round trips to their depot).
No problems with tyre wear and sadly I don't know any dragster racing diff rebuilders.
At least I've now got a few more specific questions to go back to them with on Monday......
Silver-Fox
LIFE MEMBER
Have a lot ok on some drag racing forums.
Generally nice helpful people.
I know what you are saying about cost but if the truck place hasn’t fixed the problem then surely it’s down to them to sort.
Is it worth getting a second hand axle and swopping for yours to eliminate a diff issue?
Would need half shafts left in the second hand one but no breaks required if issues are unloaded for test?
“Drive it” whilst chocked up off floor.
Again not a cheap test but your going backwards at the mo unfortunately.
There must be loads of scrap sprinters around.
Generally nice helpful people.
I know what you are saying about cost but if the truck place hasn’t fixed the problem then surely it’s down to them to sort.
Is it worth getting a second hand axle and swopping for yours to eliminate a diff issue?
Would need half shafts left in the second hand one but no breaks required if issues are unloaded for test?
“Drive it” whilst chocked up off floor.
Again not a cheap test but your going backwards at the mo unfortunately.
There must be loads of scrap sprinters around.
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OP
OP
Parapilot
Free Member
Logical, but at £720 for a used axle (of unknown condition and mileage), at least £150 delivery, £500 fitting (plus the same to replace mine afterwards) it's just not practical to see if it makes any difference.
Sady the usual Sprinter parts just don't fit mine.
Mercedes instructed Truck Transmissions to fit the diff and won't accept there is a problem with the parts they supplied unless I can prove it, so I'm kind of stuck between them now.
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Another slim possibility but worth considering
I suspect that your vehicle has two ecu’s one for the engine and another for the transmission, either of these if at fault could cause gearchange problems.
Also I’ve seen a Merc car with all the symptoms of an automatic transmission fault that was fixed by curing an engine problem that the owner was unaware of.
I suspect that your vehicle has two ecu’s one for the engine and another for the transmission, either of these if at fault could cause gearchange problems.
Also I’ve seen a Merc car with all the symptoms of an automatic transmission fault that was fixed by curing an engine problem that the owner was unaware of.
Silver-Fox
LIFE MEMBER
Can’t we have a let’s fix your vehicle meet at yours?
You supply somewhere to stop, bacon rolls and somewhere for the wives to shop and we can fix your van
Could you “hire” an axle collect yourself.
Can’t be more than a few hours to swap an axle without touching the breaks.
Where in the country are you?
You supply somewhere to stop, bacon rolls and somewhere for the wives to shop and we can fix your van
Could you “hire” an axle collect yourself.
Can’t be more than a few hours to swap an axle without touching the breaks.
Where in the country are you?
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OP
OP
Parapilot
Free Member
If you can fix it on my driveway without a 6 ton lift then I'll supply unlimited bacon rolls and even a credit card for your wives to shop with !
I'm between Liverpool and Warrington just off M62.
OP
OP
Parapilot
Free Member
Yes, and it has had a mild engine remap in the past so I'm considering an ECU swap just to rule anything out....
You have done your best you cant do much more. The problem was there before the diff was changed and is still there. I dont know if you have changed the UJs and centre bearing in the prop but that would be my last throw at it.
If that was my van after spending £10,000 I would just run it until some thing really does show itself and becomes obvious. John
If that was my van after spending £10,000 I would just run it until some thing really does show itself and becomes obvious. John
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With that style of diff I would drain the oil from the diff, remove the rear diff cover and then take a good look at it whilst moving propshaft.
That would only cost a gasket if it’s required, and possibly new oil, although the old could be put back in.
But I understand it’s not so easy if you aren’t doing the fixing yourself.
That would only cost a gasket if it’s required, and possibly new oil, although the old could be put back in.
But I understand it’s not so easy if you aren’t doing the fixing yourself.
OP
OP
Parapilot
Free Member
A bit like this you mean ??
I've looked in it several times over the past year, felt the backlash, changed the oil, sniffed it and scoured it with my fingers for wear or any metallic debris. Setting up a diff is beyond my technical capabilities (and requires specialist tools) so I've had to trust the 'experts' to do this. Hard to believe they could get it wrong at several different places and even with the new parts.
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That isn't even a hypoid bevel - setting it up is neither very technical nor difficult. If it looks OK it'll be OK. Backlash (tooth clearance) should be around 0.010" to 0.020" pinion to crownwheel.
sallylillian
LIFE MEMBER
I do enjoy these threads, where there are people with obvious knowledge debating contiguously without purile interruption. I will continue to watch this thread like reading a John Grisham.
Is one of those bearing caps on the wrong way round ?
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Read right through the whole post , looked at your video, parts diagram and photo on page 5.
I am a retired transmissions engineer who used to work at Land Rover , Iam very familiar with props and axles. However, I am not an expert on Noise Vibration and Harshness or NVH as we call it.
My first observation would be that you have tried heroically to fix the issue and have spent lots of money and time on it. You really have tried hard and had I not rear the whole thing I would have suggested all the things posters have suggested already.
So here are a few one liners , i am sorry ,none of these are a solution, i'm just trying to help.
Rear axle backlash , many have commented that it seems too large. Looking at the video etc. this does seem a little high , but it's not in my opinion miles out and I don't think it's a root cause. But you never know. @tonyidle makes some good points. It's a spiral bevel , I think (where the prop or pinion is on the same centreline as the crownwheel. Looking at your parts diagram , it looks like backlash is adjusted by turning the cage nuts, part number 90 after removing the little blocker or locking pins, part number 100 on top of the bearing caps. This can only be done after loosening the caps and then applying a set torque to the nuts so that the diff case can move sideways when the cage nuts are turned. You would for instance move one nut say 4 'holes' in and the other side 4 holes out, so that the bearing preload does not change. It looks like this can be done by knocking them round using the gap between the axle case and the bearing cap.
I mention this only to indicate that backlash looks like it could be adjusted if required without removing the axle from the vehicle.
Don't confuse backlash with pinion mounting position (position of the pinion from the crownwheel centre. As @tonyidle mentions if this was seriously out you would have a whine problem , not a clonk.
I know this does not really help you.
Propshaft.
Again as @tonyidle points out , it looks like the UJ angles are very low , possibly close to straight. This is not good for the UJ needle roller bearings. UJ's should run constantly at above about 2 or so degrees because under these conditions the needle rollers 'process'. In other words they rotate around their own centre or axis and they also rotate around the bearing track. Too low an angle and they just rock too and fro causing rapid wear.
I know you have had the prop checked , more than once , but I would want to check the UJ's move smoothly without any lumpiness, simply tested by hand on the removed prop.
Removing the centre bearing spacer just as a trial is worth doing and quick and easy to do. As it adding only temporarily spacers to go towards the road as well.
The prop shaft does not look out of balance. I would agree with MB there.
Not sure if you can see it in the video but again I think it was @tonyidle who noticed the UJ's were in line. This as he mentions is not a good idea. UJ's suffer from angular velocity variation as they rotate and are usually put 90 degrees out of phase. But this is a MB design issue and all vehicles would show a problem if this was the root cause.
Normal longitudinal movement of the prop can be seen at the spline near the centre bearing and this looks normal apart from the occasional big 'spike'. I confess I can't think of what causes this given that your problem is a light load issue. It's possible the prop just gets excited (in the resonant sense) momentarily.
You might try changing the resonant frequency of the various propshaft sections by adding mass or weight. This would have to be by adding a circular , doughnut shaped object to maintain balance , not that easy.
The best way to try this would be to make up a disc that you could bolt onto the rear axle flange and then bolt the prop to it. This would act as a small flywheel and may stop the propshaft 'tube' bouncing across the backlash. Make this a fair diameter within reason but relatively thin to maintain the propshafts plunge capability.
Oh well , ramblings really.
I hope you fix it and I will watch with interest.
I am a retired transmissions engineer who used to work at Land Rover , Iam very familiar with props and axles. However, I am not an expert on Noise Vibration and Harshness or NVH as we call it.
My first observation would be that you have tried heroically to fix the issue and have spent lots of money and time on it. You really have tried hard and had I not rear the whole thing I would have suggested all the things posters have suggested already.
So here are a few one liners , i am sorry ,none of these are a solution, i'm just trying to help.
Rear axle backlash , many have commented that it seems too large. Looking at the video etc. this does seem a little high , but it's not in my opinion miles out and I don't think it's a root cause. But you never know. @tonyidle makes some good points. It's a spiral bevel , I think (where the prop or pinion is on the same centreline as the crownwheel. Looking at your parts diagram , it looks like backlash is adjusted by turning the cage nuts, part number 90 after removing the little blocker or locking pins, part number 100 on top of the bearing caps. This can only be done after loosening the caps and then applying a set torque to the nuts so that the diff case can move sideways when the cage nuts are turned. You would for instance move one nut say 4 'holes' in and the other side 4 holes out, so that the bearing preload does not change. It looks like this can be done by knocking them round using the gap between the axle case and the bearing cap.
I mention this only to indicate that backlash looks like it could be adjusted if required without removing the axle from the vehicle.
Don't confuse backlash with pinion mounting position (position of the pinion from the crownwheel centre. As @tonyidle mentions if this was seriously out you would have a whine problem , not a clonk.
I know this does not really help you.
Propshaft.
Again as @tonyidle points out , it looks like the UJ angles are very low , possibly close to straight. This is not good for the UJ needle roller bearings. UJ's should run constantly at above about 2 or so degrees because under these conditions the needle rollers 'process'. In other words they rotate around their own centre or axis and they also rotate around the bearing track. Too low an angle and they just rock too and fro causing rapid wear.
I know you have had the prop checked , more than once , but I would want to check the UJ's move smoothly without any lumpiness, simply tested by hand on the removed prop.
Removing the centre bearing spacer just as a trial is worth doing and quick and easy to do. As it adding only temporarily spacers to go towards the road as well.
The prop shaft does not look out of balance. I would agree with MB there.
Not sure if you can see it in the video but again I think it was @tonyidle who noticed the UJ's were in line. This as he mentions is not a good idea. UJ's suffer from angular velocity variation as they rotate and are usually put 90 degrees out of phase. But this is a MB design issue and all vehicles would show a problem if this was the root cause.
Normal longitudinal movement of the prop can be seen at the spline near the centre bearing and this looks normal apart from the occasional big 'spike'. I confess I can't think of what causes this given that your problem is a light load issue. It's possible the prop just gets excited (in the resonant sense) momentarily.
You might try changing the resonant frequency of the various propshaft sections by adding mass or weight. This would have to be by adding a circular , doughnut shaped object to maintain balance , not that easy.
The best way to try this would be to make up a disc that you could bolt onto the rear axle flange and then bolt the prop to it. This would act as a small flywheel and may stop the propshaft 'tube' bouncing across the backlash. Make this a fair diameter within reason but relatively thin to maintain the propshafts plunge capability.
Oh well , ramblings really.
I hope you fix it and I will watch with interest.
Last edited:
WSandME
Free Member
At some point, shouldn’t you get some other type of experts involved: Mercedes Management, Mercedes Public Relations, Trading Standards, Twitter - anything to get those that should know how to fix it to get their a55es into gear and fix the problem.
However - here’s a long shot.
During research into my own problem (mentioned earlier - differential) I came across a diagnostic tool which may only be available in the US, but...
This was a device which recorded all the vibrations made by the vehicle whilst driving through all stages - low gear to high, back down again. Accelerating, decelerating, braking. The resultant waveform is analysed and broken down to frequency bands. For example, at a particular speed and gear, vibration frequencies can be determined for camshaft, valve train, crankshaft, pistons, gears, propshafts, UJs, differential gears, wheel bearings... As the driving regime changes (load / no load, accelerating / decelerating) the waveforms may show that eg a wheel bearing is rumbling, or that the second gear cogs are the problem.
Has anyone come across this in the UK?
However - here’s a long shot.
During research into my own problem (mentioned earlier - differential) I came across a diagnostic tool which may only be available in the US, but...
This was a device which recorded all the vibrations made by the vehicle whilst driving through all stages - low gear to high, back down again. Accelerating, decelerating, braking. The resultant waveform is analysed and broken down to frequency bands. For example, at a particular speed and gear, vibration frequencies can be determined for camshaft, valve train, crankshaft, pistons, gears, propshafts, UJs, differential gears, wheel bearings... As the driving regime changes (load / no load, accelerating / decelerating) the waveforms may show that eg a wheel bearing is rumbling, or that the second gear cogs are the problem.
Has anyone come across this in the UK?
OP
OP
Parapilot
Free Member
Wow - thanks @Jake Royd - very informative stuff !
I don't plan to make any adjustments to the diff, backlash or anything myself but it is very useful to know that info when discussing with the mechanics.
Prop was my starting point a year ago and comments about it being 'too straight' are correct (which I initially thought was a good thing). UJ's do not feel worn or loose, and move smoothly except for at the very centre position which feels a little looser. I've asked about this several times and been told "new ones would feel tighter but be just like this after 6 months of regular driving". Only one guy (Dean at Truck Transmissions in Blackburn) described them as 'notchy' and said he would replace them if it were his own van. He was overruled by his boss and every other specialist including Firow Propshafts said they are fine.
I will try removing the centre bearing spacer tomorrow as that is an easy thing to try. I will also check UJ's are at 90 degrees to each other. Pretty sure they were when I took it off and it had yellow alignment marks painted on already which I matched up again. Would hope the other mechanics haven't made such a blindingly obvious mistake but who knows ?
@WSandME - I have a 12 page complaint lodged already with Mercedes customer assistance. It will make you cry but will have to be on another thread as it is so convoluted ..... Basically I was sent to at least 11 dealerships across 7 European countries, including the main factory in Munich, 2 others in Germany, Belgium, Austria, Slovenia, Croatia, Serbia and Macedonia !! Plus a few in the UK of course. This makes it difficult for Trading Standards to investigate but there may well be legal action ahead.
Mercedes has a kit of microphones to do exactly what you say. A dealer in Austria had it but we ran out of time (and their weekend rates were astronomical). My UK dealership also had one but somebody drove over it .....
You can trust me that this problem has caused hundreds of phone calls and emails so far, and many hundreds of hours of my time......
I don't plan to make any adjustments to the diff, backlash or anything myself but it is very useful to know that info when discussing with the mechanics.
Prop was my starting point a year ago and comments about it being 'too straight' are correct (which I initially thought was a good thing).
UJ's do not feel worn or loose, and move smoothly except for at the very centre position which feels a little looser. I've asked about this several times and been told "new ones would feel tighter but be just like this after 6 months of regular driving". Only one guy (Dean at Truck Transmissions in Blackburn) described them as 'notchy' and said he would replace them if it were his own van. He was overruled by his boss and every other specialist including Firow Propshafts said they are fine.I will try removing the centre bearing spacer tomorrow as that is an easy thing to try. I will also check UJ's are at 90 degrees to each other. Pretty sure they were when I took it off and it had yellow alignment marks painted on already which I matched up again. Would hope the other mechanics haven't made such a blindingly obvious mistake but who knows ?
@WSandME - I have a 12 page complaint lodged already with Mercedes customer assistance. It will make you cry but will have to be on another thread as it is so convoluted ..... Basically I was sent to at least 11 dealerships across 7 European countries, including the main factory in Munich, 2 others in Germany, Belgium, Austria, Slovenia, Croatia, Serbia and Macedonia !! Plus a few in the UK of course. This makes it difficult for Trading Standards to investigate but there may well be legal action ahead.
Mercedes has a kit of microphones to do exactly what you say. A dealer in Austria had it but we ran out of time (and their weekend rates were astronomical). My UK dealership also had one but somebody drove over it .....
You can trust me that this problem has caused hundreds of phone calls and emails so far, and many hundreds of hours of my time......
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A long shot but is it possible that the sliding joint on the prop can be separated and UJ phase angle changed that way ?
@WSandME mentioned frequency or order analysis. I've been involved in some of this. Briefly gears produce an order and several side orders linked to the number of teeth. Analysis tells you where these orders produce the most energy and hence vibration and hence noise throughout. The speed range.
But this is a design and development tool not really a tool for individual vehicles.
It's possible that you do have a problem with resonances due to perhaps having an uprated axle and slightly non standard prop? Which was not looked at in development. But unlikely.
Most severe NVH issues come in and out at various speed ranges which is not your problem.
But they also occur at light loads.
The mini flywheel idea sounds like worth trying because it modifies the inertia of the complete rotating system and your problem seems to me to happen on float.
@WSandME mentioned frequency or order analysis. I've been involved in some of this. Briefly gears produce an order and several side orders linked to the number of teeth. Analysis tells you where these orders produce the most energy and hence vibration and hence noise throughout. The speed range.
But this is a design and development tool not really a tool for individual vehicles.
It's possible that you do have a problem with resonances due to perhaps having an uprated axle and slightly non standard prop? Which was not looked at in development. But unlikely.
Most severe NVH issues come in and out at various speed ranges which is not your problem.
But they also occur at light loads.
The mini flywheel idea sounds like worth trying because it modifies the inertia of the complete rotating system and your problem seems to me to happen on float.
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I've sent your first post with video to one of my colleagues who is more experienced with these issues than I am.
Silver-Fox
LIFE MEMBER
The thing I’d be asking is thisvthe only vehicle of this particular design and assembly.
If not has there been other cases as this one or is this isolated case.
Has this been doing it from day one, if so wouldn’t it have already been back to manufacturer?
If it was ok from new surely it is a wear type issue some where along the line.
Was it like it when the op bought it?
If not has there been other cases as this one or is this isolated case.
Has this been doing it from day one, if so wouldn’t it have already been back to manufacturer?
If it was ok from new surely it is a wear type issue some where along the line.
Was it like it when the op bought it?
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I agree
Flexi plate, has it been checked or replaced?
We had exactly the same van, Hymer S820 on exactly the same chassis, engine, gearbox, propshaft, diff etc and not an ounce of trouble. This is the first time I have heard of a problem on a Hymer Merc 616 so I would say probably an isolated case. The OP said that it didn't have a lot of history when he bought it and no one knows how the previous owners treated it and where they went/what they did to it.
From what I have heard the chassis/gearbox and set up are usually bullet proof. The engine a bit underpowered when lugging 6.4 tonne around on anything but flat or downhill, was the only thing I noticed.
This was ours. Absolute quality throughout. Built from girders.
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