Why would you do that, Mazda?

davekmoore · Postby **davekmoore** » Thu Aug 31, 2017 1:59 pm

Now, I have recently and finally been shamed into buying some tools. And then I wanted to change the diff oil, and discovered that not only have Mazda put giant bolts in there, but that they're also 2 slightly different sizes - 23mm and 24mm heads with the same thread diameters. Why would they do that unless they have shares in Kincrome!?

Then discovered the drain and fill plugs had previously been put in the wrong way round. All the more reason to work out how to do more of my own work.

speed · Postby **speed** » Thu Aug 31, 2017 2:21 pm

davekmoore wrote:Now, I have recently and finally been shamed into buying some tools. And then I wanted to change the diff oil, and discovered that not only have Mazda put giant bolts in there, but that they're also 2 slightly different sizes - 23mm and 24mm heads with the same thread diameters. Why would they do that unless they have shares in Kincrome!?

Then discovered the drain and fill plugs had previously been put in the wrong way round. All the more reason to work out how to do more of my own work.

Good on you for doing the job yourself.
One of my cars has both imperial and metric bolts. It annoys the crap out of me whenever i do work on it.

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hks_kansei · Postby **hks_kansei** » Thu Aug 31, 2017 3:35 pm

For things like that it's probably as simple as different sizes meaning there's no chance of accidentally swapping the bolts (if there's a difference in them other than size)

Thankfully you can easily buy single spanners and sockets.
I tend to also have a cheap set of sockets for this stuff, and times when I need to modify one for a specific use (like the specially bent/twist one I made for removing bellhousing bolts in the kingswood without tilting the engine)

Lokiel · Postby **Lokiel** » Thu Aug 31, 2017 4:55 pm

hks_kansei wrote:For things like that it's probably as simple as different sizes meaning there's no chance of accidentally swapping the bolts (if there's a difference in them other than size)
:

... if that was the original intent, then the threads should have been different too

It wouldn't surprise me if the mis-matched bolt isn't OEM (ie. at some time in the car's history, the bolt was removed and misplaced and a different head-size used).

davekmoore · Postby **davekmoore** » Thu Aug 31, 2017 5:26 pm

YouTube videos also talk about 23 and 24mm. The ideal tool is a long straight spanner - not angled, not offset. Car should be on a hoist really. I (just) managed with ramps and axle stands.

manga_blue · Postby **manga_blue** » Thu Aug 31, 2017 5:52 pm

The main thing is to crack the top plug before you take out the bottom plug and drain it. Nothing's worse than draining a diff and then finding you can't get fill it.

As far as workshops go, I saw a photo of a diff drain hole plugged with a wheel lug bolt from a truck plastered witth silicon the other day - done by a mechanical workshop. I do all my own work - it's less effort. :roll:

Mr Morlock · Postby **Mr Morlock** » Fri Sep 01, 2017 1:48 pm

OE engineers normally choose fastener sizes for a reason- its certainly not random- i.e. these specified on all drawings/ data and Mazda like the others tend to use a range i.e. avoiding specials. I doubt if any OEM uses imperial and metric on the one car. DIY is ones own choice.

speed · Postby **speed** » Fri Sep 01, 2017 2:47 pm

Mr Morlock wrote:OE engineers normally choose fastener sizes for a reason- its certainly not random- i.e. these specified on all drawings/ data and Mazda like the others tend to use a range i.e. avoiding specials. I doubt if any OEM uses imperial and metric on the one car. DIY is ones own choice.

I think you'll find that a rover mini is an exception.

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bruce · Postby **bruce** » Fri Sep 01, 2017 4:17 pm

Yup, difft sizes for that exact reason. Drain plug is magnetic too (I think).

hks_kansei · Postby **hks_kansei** » Fri Sep 01, 2017 5:59 pm

Mr Morlock wrote:. I doubt if any OEM uses imperial and metric on the one car. DIY is ones own choice.

Not so much these days, and not so much Japanese cars.

But Aussie cars like the HZ kingswood do, since it was built in a weird time when the metric Commodore was starting production while the older kingswood was still produced, and there was some very annoying cross pollination so to speak.

I believe a few more modern USA cars mix as well, when they'd have a European/Japanese supplied generic component used during production.

davekmoore · Postby **davekmoore** » Sat Sep 02, 2017 1:45 am

Pic below of the two bolts showing how well they fit in 34 and 23mm sockets. The one one the riht should have been the lower one as it has the magnet. They were the opposite way round and on so tight on with no anti-sieze that sockets wouldn't budge them and had to resort to using Thor .

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