Definitive diff mount answers?

[MadAussie]

Well Wyatt from StreetUnit has been quite helpful so far, and I'm leaning back towards the SURE front diff mount (Apparently the new design hasn't had any reported failures?), and the guys at Edge are letting me know asap when the cp-e mounts come in.
It can be said that both companies have good quick customer service, so if nothing else that's nice.

[kmh001]

I'm leaning back towards the SURE front diff mount (Apparently the new design hasn't had any reported failures?)

Yet. Hope you're not the first. It's made of aluminium and bolted together. Even aircraft use steel for high-stress components like these.

It can be said that both companies have good quick customer service, so if nothing else that's nice.

It's a shame the customer service at sure doesn't extent to after sales support when their products fail to perform as claimed.

Sorry about all the negativity but I'm out of pocket more than $3000 because their design was so badly flawed and they've flatly refused to do anything customer service-like to help. Their lifetime warranty is worthless.

[MadAussie]

Though was it the forward or the rear mount that failed on yours?
Also, was it the original design, or the 'updated' one?

:-/

[kmh001]

It was the original design rear mount. Both sure mounts are now made of aluminium.

[MadAussie]

Fair do - I've ordered the CPe rear mount (Does look far better), but since the front mount is pretty much just a hanger, I'll see how this goes.
But yeah, aaarg so many things to take in when you're buying from overseas

[SarcasticOne]

http://www.mazdaspeedforums.org/foru....php?p=1261848

Cpe is seriously understaffed... so don't take it out on edge

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[Matto]

Just spoke to people from therpmstore and they told me they'll have the CPe Rear diff mount in stock next week =)

[MadAussie]

So, the new mounts are here. However, looking under the car tonight, I can see that one of the mounts bolting points on the front diff housing has broken off.
The stud has sheared in the hole closest to the prop shaft, but the second one on this mount has actually broken the tab on the diff case.

Who do I talk to in WA to work out either a new casing, or can I repair it somehow?
I'm thinking I'll just put the sure mounts in for the time being (it mounts to three other locations) and be gentle...


This isn't my photo, but to give a better image, it's the one on the left that's broken off. It hasn't ruptured the diff itself, just taken off the top half of the tab

[Doug_MPS6]

Looks rather like the tab failed then the reduced support and additional movement stress the other bolt/stud to the point of shearing.

It's no fun chasing a new diff casing. Even making a new tab and welding it on, if such a thing is possible or wise, is a major pain in the butt. It'd be hard to have confidence in that weld unless the entire diff was removed and emptied and thoroughly cleaned and the tab was properly constructed, aligned and mig welded onto the (possibly pre-heated) housing.

Plainly it pays to get these checked every service for obvious signs of looseness, cracking or wear. I asked my Mazda dealer to check the diff mounts last time I was in for service (65,000km) and they assured me all was fine, but I really have no idea if they even looked at it. I guess I only feel comfortable doing my own checks.

But this is a salutary reminder to do it.

[MadAussie]

Here's my one



To be honest, my options I'm considering are:
1. FInd a second hand OEM housing, maybe off a cx-7/9? Is that front casing the same?
2. Go to a fabricator for a billet housing to be made up. Is that front case just like a cup to go around the mechanicals inside? Or is there bracing/ mount inside I need to be aware of?
or 3. Have a steel loop made to wrap around the housing, maybe bolting to some lower points too, to simulate the turbine tech mount.

Really, I'm thinking that the SURE mounts two extra mounting points will be enough to hold it up while I figure it all out. Just don't need a broken axel or two to go with this. Sigh

[Doug_MPS6]

Looks like you can't win with this design setup, bcs:

1. Torque the fittings up too tight and you risk stripping threads or over-stressing the tab and surrounding casing area so it fails.
2. Don't torque it up enough and it works loose, then strips the threads or shears the bolts and possibly buggers the tabs too.

Suggests to me that, learning from the experience of others, the best thing is to take pre-emptive action to capture the diff with a well-made robust mount, although it is a pity that, as I note above, the diff attachment points remain a weak area regardless of how strong a mount is, and short of finding additional mounting methods, perhaps including some kind of load-bearing cradle if it were possible to fit one, will remain so.

I must have a harder look at mine soon. No reason to suspect there is an issue now but I'd feel more comfortable checking before it becomes an real problem.

[kmh001]

The Turbine Tech mount attaches with five bolts, if you leave one out you'll still have four, which is better than two or even none. The TT mount is made from steel. The sure mount is made from 6061 aluminium. You need to understand the material properties of aluminium - it's softer and more brittle than steel. I don't know what steel is used in the TT mount but assuming it's something like 4130, the tensile strength would be two to three times greater than aluminium; furthermore the yield strength of T6-6061 is 35,000 to 45,000 psi while the yield strength of 4130 is 70,000 to 85,000 psi. Not only that, the sure mount only has four attaching bolts so the stress loads are concentrated into a smaller area (ie higher), and it's bolted together which is not a strong as a welded joint. Bolting aluminium together like that is pretty cheap. If they were fair dinkum about using 6061 they would have machined the mount in one piece from billet stock.

With a damaged housing like yours the sure mount looks like a huge risk. In fact I wouldn't risk the sure mount with an undamaged diff let alone one that's damaged.

In your situation I would probably take a chance with the TT mount minus one bolt and save the trouble and expense of replacing the diff housing. Even if it proved to not have sufficient strength (which is unlikely) the consequences would be minimal and you'll be no worse off than you are now.

[MadAussie]

Turbine Tech mount didn't end up being an option, no one could tell me when one would be in stock. Having the diff flailing around is enough of a reason to just get this one in and see how we go.
I'll make a steel loop for it if this looks like it's going to cause dramas.

And still haven't found anyone who can provide any information on how much a new casing is worth or where I'd get one from, even though everyone seems to say they fail??

[MadAussie]

OK guys, mounts are in, and it's creating a variety of different noises now, some which I figure are front-of-the-car related, but this morning it did a strange 'binding' sort of feeling going into third gear, followed by a thud, then accelerated normally.

Is there anyone in Perth that would be willing to wander down my end of town (Jandakot/cockburn) to take it for a drive and see if you can identify the noises it's making?

[SarcasticOne]

Tuned?
Sounds like the WOT hesitation

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[MadAussie]

No not tuned, however this was a more mechanical feeling. The only way I can describe it is maybe the prop shaft loading up the bushes, and then releasing it with either the box or the diff slapping down. Was a bit strange, going to get the car in the air thisevening and inspect everything I did last weekend. These tuning hand controllers, do they have to remain plugged in to function? Or can someone rock up, turn off the WOT hesitation, and take the unit back home with them?

I think I need to buy a welder and just start bracing the shit out of everything, lol!

[Doug_MPS6]

Sounds like some form of AWD transmission wind-up. Does it do it all the time or just the once? Had you been on full lock on a hard surface, esp in reverse, immediately prior? Once the diff oil is warm, the plates should not bind, but they will sometimes if it cold. If your car has been standing for a while when you have been fixing this issue, it might have stiffed up a bit. See if it improves after a drive. Chs

[MadAussie]

Only did it once today, the mounts were done on Thursday/Friday last week with no strange noises in between then.
It was after about 10 minutes of driving, car was warm. Thanks for that though, its certainly food for thought.

Next week I'll be doing a full fluid swap in the driveline, so I'll have a chance to give it a solid inspection., might take the prop shaft out and look at the uni joints too.
Would the engine/gearbox mounts now be having dramas from the extra stiff rear?

[kmh001]

Drive line binding in these cars is exacerbated by variation in tyre height. It may sound obvious but the first thing I would check is tyre pressure, then use a tape measure and a flat level surface to confirm all four tyres have 4mm or less variation from ground to the top of the wheel rim.

[MadAussie]

Cheers! Will take a look at that thisevening mate!