DMCH Lower ball joints IS THIS WHY THEY FAIL??????

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DMCH Lower ball joints IS THIS WHY THEY FAIL??????

Postby Darren C » Mon May 02, 2011 4:18 pm

I know a lot has already been said about DMCH lower ball joints, but I thought I should let you know of what I found today.

Back in 2007 when I imported my car I bought a set of lower ball joints from DMCH as part of the "restoration". As it happened I only needed to use one on the RH side (the LH side was ok).
I fitted the lower joint and as most do put the split pin in facing forward (its easy to get in this way).
I enjoyed using my car and had done about 1000 miles when I heard of the "horrors" of DMCH lower ball joint failures. Following a long conversation with Steve Wynne, and James at DMCH, it was agreed the ball joints needed to be put in the car with the split pin facing left to right (to allow the grease channel in the joint to put grease where needed on the pivot ponts) There's a video Steve did on this too.

Anyhow, following this advice I rotated my RH DMCH joint and put the pin in left to right. (This is a sod as it hits the hub, but just about do-able) That was at 1000 miles ish on the new joint.

Well yesterday I noticed wheel wobble just like unballance wheels transmitting through my steering. I went and saw my tame tyre fitter today and checked the ballance again...all was fine? We got the car on the lift and had a good poke around, found nothing????

Drove home and noticed the wheel wobble was only happening when coasting (ie foot off throttle) or when braking. I discounted any disc warp because it wobbled without braking, cant be wheel bearings as new and no play when jacked up, cant be the rack because it's new too????

Not happy we couldn't find anything at the garage, I jacked the car up and violently rocked the wheels...NO PLAY?
ok...I then took off the front wheels and with the frame on axle stands, I carefully jacked up the front suspension under the tube in the lower arm where the anti roll bar fits. This compressed the spring and put the suspension in the same position it would be if the car was sitting on its wheels. Put the wheel back on and rocked again.

OMG :shock:

The play in the DMCH lower joint was ridiculous...it was absolutely shagged...and only after 2500 miles!

Took it out of the arm and got out my other DMCH joint that I bought at the same time but never fitted, and compared the two. (You can recognise DMCH joints as they have the word "armstrong" molded on the rubber boot)

They looked the same, so did I risk fitting another? Hmmmmm. I took the rubber boot off the old shagged joint and noticed the grease in the joint was hard and crumbly. I took the rubber boot off the new joint and noticed the grease in the new unused joint was hard and crumbly :shock:
I cleaned the NEW joints grease out and saw that the body of the joint where the circlip fits was "blued". (caused by excessive heat)

Now then....I know DMCH buy in these joints (ex VW) then machine them to fit the Delorean (by turning on a lathe to put the circlip grove in them). Have I just stumbled over the REAL REASON DMCH joints fail? I cleaned up the OLD joint it was blue too!
Me thinks they have machined these on a lathe with a tipped tool (ceramic composite) which needs no coolant. The down side is the joint gets so HOT it blues the body of the joint and BURNS THE GREASE inside the joint.
With BURNT grease in the ball joint, there is little lubrication, with blued metal the steel hardness is affected.

Now then...It's over to you Mr Wynne...

As a trial on behalf of the UK Delorean community I have repacked (with new grease) my unused blued and burnt grease filled DMC joint and fitted it to my car. As a gesture to DMCH I've put the split pin in Left to Right. Mileage recorded 64043. Now lets see how it performs. I can do no more.

I'll bring the old failed 2500 mile joint to Eurotec.

Regards
D

PS, Anyone with these DMCH joints (or any other for that matter) are advised to check the free play as above, my car just passed its MOT and unless you support the suspension as I said above...you'd never know you have play in the joint. I'd also advise poping the rubber boot off your joints and using the grease nipple on the underside, regreaseing them until you see new grease exit the top.
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Re: DMCH Lower ball joints IS THIS WHY THEY FAIL??????

Postby arranj » Mon May 02, 2011 4:46 pm

Nice write up Darren.

Just to clarify though - the modified/machined VW Beetle ones are the ones that Special T Auto (John Hervey) sell (and we have stocked in the past until both you and Phil Emsley pointed out the poor quality of the modification on some of them) and have been the "ball joint of choice" in recent times due to the numerous failures of the DMCH ones. I and many others have the Special T Ball Joint on our cars - normally can be spotted by "lack of grease nipple", although I know some earlier ones had the nipple too.

The DMCH ones were specially made. This is Steven Wynne's explaination as to why the DMCH ones fail: (video from 6 months ago)





Failure reference threads:

viewtopic.php?f=66&t=505&start=40

viewtopic.php?f=18&t=1433&start=18

viewtopic.php?f=13&t=490


And this is what happens when a lower ball joint fails: viewtopic.php?f=20&t=470
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Re: DMCH Lower ball joints IS THIS WHY THEY FAIL??????

Postby Darren C » Mon May 02, 2011 5:00 pm

Thanks Arran,

But the point I'm making here is about the OVER HEATING of the joint in manufacture which is burning the grease they are pre-packed with.
(unless this is done before assembly, which wouldn't explain why the grease in my new unfitted joint was hard and crumbly?)
Here's a picture of what I mean.

Image

Image

Steel has to get to around 300 deg C to blue like this!

Whatever you may think this is the result of POOR manufacturing to allow this sort of overheating of a machined component.
Last edited by Darren C on Mon May 02, 2011 5:11 pm, edited 1 time in total.
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Re: DMCH Lower ball joints IS THIS WHY THEY FAIL??????

Postby A Van » Mon May 02, 2011 5:10 pm

Well you know what your talking about Darren....

If you bring the joint to Eurotec, I am sure Stephen will be only too pleased to have a discussion about it.
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Re: DMCH Lower ball joints IS THIS WHY THEY FAIL??????

Postby Darren C » Mon May 02, 2011 5:22 pm

Cheers Al,

Having just watched Steve Wynne's video...like a hawk...the un assembled joints on his bench have NO blueing, but the one he holds up against the car to show you the split pin position does????

When the steel has been Blued like this it will tend to ANNEAL the metal. This partially re-aligns the crystaline structure which results in a SOFTENING of the metal.

Now combine that with this issue Steve raises about the radius of the grove edge on the ball, you have a combination for disaster. Especially as the ANNEALED area is where the ball grove wears the body. :shock:

Personnally I don't buy the radius edge on the ball grove as the main culprit, admittedly it wont help. I place my money on the softened (annealing) of the "cup" by this overheating on manufacture.
DMCH can put a radius on...that can only help...but they HAVE TO stop this overheating to cure the problem fully.
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Re: DMCH Lower ball joints IS THIS WHY THEY FAIL??????

Postby dmc4087 » Mon May 02, 2011 5:59 pm

Great work Darren, I like your theory.

Why anyone is still running these balljoints is beyond me though - not worth the danger at all.
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Re: DMCH Lower ball joints IS THIS WHY THEY FAIL??????

Postby A Van » Mon May 02, 2011 7:09 pm

Agreed Thomas, although with as much feedback as possible maybe the problems can be ironed out once and for all.
Its in all of our interests to have ball joints we can trust and readily available.
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Re: DMCH Lower ball joints IS THIS WHY THEY FAIL??????

Postby Admin-bloke » Mon May 02, 2011 7:10 pm

Is there an alternative out there proven to fit and work as yet?

Was the balljoint cross referenced to a metro or was this the upper balljoint?
I will have to do some searching....
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Re: DMCH Lower ball joints IS THIS WHY THEY FAIL??????

Postby tourettes tony » Mon May 02, 2011 7:16 pm

funny this should have been mentioned because a set i got off Dave H about 6 years ago both seized and i did notice the bluing but put this down to manufacturing, or was they originals i don't recall :( this seems to be a major weak point on the suspension set up and maybe a totally different approach needs to be considered TT
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Re: DMCH Lower ball joints IS THIS WHY THEY FAIL??????

Postby arranj » Mon May 02, 2011 7:37 pm

Admin-bloke wrote:Is there an alternative out there proven to fit and work as yet?

Was the balljoint cross referenced to a metro or was this the upper balljoint?
I will have to do some searching....

VW Beetle from the late 70s, although you need to modify them. There was talk of a Mazda one at some point, but again they need modifying. The "metro" I would guess is the Upper ball joint, which is a Vauxhall Viva cross reference: viewtopic.php?f=27&t=1902
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