Mazda 6 MPS Differential problems and/or solutions

[shakespeare]

Hello all,

On my way to visit a customer this morning I heard a sound which was like a metal object hitting the exhaust, then experienced some sharp knocks on downshifts, when accelerating the noise/knocks became louder. This was when I realised something was seriously wrong and as the noise was from the rear, I'm thinking diff.

Pulled over as soon as I could (about 100metres) and looked under and notice the diff was on an angle, at this point I'm thinking bugger, so called the Mazda roadside assist number, who promptly arranged a tow truck for me and within an hour I was at my friendly dealer.

Up on the hoist it became evident that two bolts which hold the cast iron mount forward of the diff had sheared off causing the diff to move around. The service manager explained that this may have been caused by having smaller than stock tyres (225/40 vs 215/45) which results in an incorrect ratio to PCM, anyway he advised that they probably won't get genuine bolts in time, so he is arranging some higher strength local bolts. He also advised that they have had this problem once before, but the guy was apparently doing alot of track work.

Anyway I should have my girl back in time for the weekend, with nice new shiny bolts which are hopefully stronger. Has anyone else experienced this little drama, or have heard about? I found a couple of references to the rear diff mount on other forums but nothing about the forward mount.
Cheers
Chris

[nickows]

Sorry to hear about this happening Chris - must be an awful sight to see your pride and joy being towed away

I havent heard of this happening with the forward mount before, just the rear mount (which is well documented). Its good to see your service manager trying to get you back on the road ASAP - call me cynical , but I doubt most service managers would go to the trouble of ordering in bolts if they couldn't be sourced from Mazda.

Hope the beast is up and running again soon

[EVILMPS]

Jeebus Shakes! I think i would have crapped myself!!
Good news with the dealer there, gotta agree with nockows.
Which dealer do you go to? Might be worth giving them and your service manager a plug here

[blackbetty]

Ohhhh that sucks, would bring a tear to my eye. Sounds like your Mazda are good though which is nice to hear.

OK your explanation of running different tyres than stock possibly contributing to the situation ... can you explain it a bit more for someone like me that doesnt really understand

[kmh001]

Mate there is heaps of discussion about broken front diff mount bolts on the US forums. Usually the bolts shear, rather than the mount breaking, but the mount does sometimes fail. Owners have often reported finding these bolts have backed out, which is believed to be the precursor to failure. This failure mode was prevalent enough to prompt Turbine Tech to develop their massive front diff mount.

Whenever I'm under my car I check the torque on these two bolts just to be sure.

It's another example of how MPS6 owners are really just unpaid beta testers for new Mazda technologies. The evidence of the design flaw can be found by comparing the MPS6 front diff mount to the CX7 front diff mount. With a similar vehicle mass but less power, the CX7 gets a much stronger mount.

BTW it's good that your dealer is looking after you, but the tyre size excuse is a load of horse ****.

[Birdhouse]

A good thing it was picked up when you did and not any later.

I'm with the last two posts and fail to comprehend how the little difference in 225/40 vs 215/45 mm but yet same rolling diameter left to right (and assume front and rear) and cause the diff bolt to shear off?

Glad to hear its an easy fix and she'll be back on the road soon.

[shakespeare]

Thanks everyone for your kind words the dealer rang me this afternoon and said all good and I can pick it up in the morning. Would've been worse to see it being towed away, fortunately I was riding in the tow truck.

Deano, I go to Wood Bros Mazda (bought the MPS there, as it was close to work), the service manager is ok, used to go to Melville Mazda (where I bought the wife's 6 and my SP23) service manager was brilliant, not sure if he is still there though.

Yeah Mel, the explanation didn't quite gel with me either and given that they've fixed it I suppose it wasn't too big an issue - from what I understood, smaller wheels = higher ratio therefore more revolutions putting stress on the diff - doesn't sound right. Mal I agree it's a load of bull, care to shed any light if there is any truth in this statement?

So hopefully I'll be back on the road tomorrow heading south for Easter, but taking the Vee-dub as it's boot is bigger and can fit all the kids stuff

[kmh001]

The tyre size thing is BS because if you increase RPM you increase revolutions, if you travel at a higher speed you increase revolutions, if you change to a lower gear you increase the torque multiplication, if you wear out your tyres the diameter decreases by 5mm which is about the difference in diameter between 225/45 and 215/45. It's just a rubbish excuse.

[Nexus]

The tyre size thing is BS because if you increase RPM you increase revolutions, if you travel at a higher speed you increase revolutions, if you change to a lower gear you increase the torque multiplication, if you wear out your tyres the diameter decreases by 5mm which is about the difference in diameter between 225/45 and 215/45. It's just a rubbish excuse.

Sure is - that's plain ridiculous. Disappointing to hear junk like that from dealers. Makes you think they have no respect for your ability to understand the vehicle.

I've gotten "all aftermarket wheels and tyre fitments are illegal" due to "match offset". And yet the same staff telling me I must match offset exactly know off-roaders get 50mm overtrack leeway.

Otherwise excellent service from them, but it makes me wonder if they think their clients are idiots. Or maybe they really believed that drivel. I don't know.

The only way tyre size could have a bearing is differing front to rear tyre sizes.

[shakespeare]

Well guys and girls, got my beast back and she's happy, new bolts no noises/vibrations yet to do a highway run to see if the resonant vibration has gone, but it is definitely smoother on WOT take off

I didn't bother discussing the tyre thing again with the service manager and he didn't raise it so obviously not a big issue for them. Got talking about other faults and he did advise buying an extended warranty when mine expires next year, about $400 so may not be a bad investment, particularly as the turbo seal issue is being discussed heavily, he did also tell me that he has had 2 cases of failed turbo seals on a 3 and 6 MPS both stock.