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The 2004-08 Acura TSX's Magnesium Transmission Case Has Some Interesting Talking Points

This little tech blog is meant to show off some of the nuance differences that came up during our recent HTSpec TSX transmission rebuild. For those who had not had the benefit of knowing much about working with this transmission, here are just a few fun factoids.

This is not an article detailing the use of Magnesium in automotive applications. For that, link to this excellent paper on the subject: AUTOMOTIVE APPLICATIONS OF MAGNESIUM AND ITS ALLOYS, by the Center for Magnesium Technology, Institute for Materials Research. In it you'll read a brief history of automotive use, strengths, and weaknesses, and all kinds of stuff that we don't really need to bore you with.

Basically, the reason to use Magnesium is that it is light weight, strong, and not exceedingly expensive. In fact much of the cost seems to stem from it being less conventional to work with, and, as such, many manufacturers are not set up to produce it (much like Titanium). Historically, Magnesium was used quite extensively in both road and racing applications. Today it is only just experiencing a resurgence.

Negatives to Magnesium are that it gets weaker the hotter it gets and there is a high risks of galvanic corrosion. A transaxle does not get remarkably hot, so the latter issue is the chiefest concern in this TSX application. If you are unaware, galvanic corrosion is a type of corrosion that happens when two dissimilar (different) metals are in contact with each other for a long period of time. Metals of different make-up will transfer electrons from one to another, and this causes a corrosive reaction that is obviously not desirable.

One of the ways Honda addresses to corrosion issue is by using these special coated washers between the mount brackets, which are steel, and the transmission case.

These little guys act as insulators, and the service manual is very specific about not loosing them.

The black bolt in this image holds the transmission case to the clutch housing. Note that they are left-hand threaded (arrow on the head is a give-away) to make sure that a person uses the correct bolts when assembling it. The black finish is again a special coating to prevent corrosion. These bolts are exclusive to the first generation TSX.

It is interesting to note the measures that need to be taken when non-conventional materials are used in manufacturing. According to the article linked above we can expect to see Magnesium more and more in the future as CAFE standards put an increasing demand on fuel economy levels. Light weight reduces the energy needed to accelerate. Or, to the enthusiast's benefit, makes acceleration faster!

Other than items like this, the TSX transmission is very similar to other K-series transmission. All of the innards are interchangeable with other models. It might be overkill to do a right up specifically on the transmission case. But then again, we feel, as first generation TSX owners, that we are fortunate to have such a well balanced car. It is engineering like the use of exclusive materials that helps make that possible. Thanks, Honda!


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