Tech Section Article on M50D was wrong

[aipaul]

I recall reading a TRS tech section article on the Mazda M50D transmission a few years ago. I seem to remember it saying it could take either ATF or 90w gear oil. It said something about the gear oil being thicker which reduced the noise and kept it from splashing around and leaking from the shift rail plugs. Because of this article I was running gear oil for a few years until I read that gear oil in this transmission is BAD! Now I see the article has been revised and all mention of gear oil removed. Anyone else remember reading the article before it was revised and following this bad advise?

 

[Gotta_gofast]

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[Earl43P]

Meh.

Your fuel mileage will go up with ATF vs. the thicker gear oil.
It didn't hurt a thing, you running gear oil.

This has been a widely debated subject for years.

 

[aipaul]

That's good to know. I notice the transmission does make more noise now with ATF in it.

 

[Will]

I recall reading a TRS tech section article on the Mazda M50D transmission a few years ago. I seem to remember it saying it could take either ATF or 90w gear oil. It said something about the gear oil being thicker which reduced the noise and kept it from splashing around and leaking from the shift rail plugs. Because of this article I was running gear oil for a few years until I read that gear oil in this transmission is BAD! Now I see the article has been revised and all mention of gear oil removed. Anyone else remember reading the article before it was revised and following this bad advise?

I've been around here since the site began and I don't remember anyone ever saying gear oil should be used in that trans. Also, since those articles were written, they have rarely been revised. There isn't a mechanism in place to revise them. Jim Oaks would have had to do it himself as nobody else has had FTP access for maybe 6 years. Back then, I had it and I know I didn't edit any articles, though I did write a few. I seriously doubt you got that bad advice here.

 

[aipaul]

Yeah my bad. I shouldn't have blamed TRS for bad info. I must have read that somewhere else or in a forum. When I first bought my truck back in 1998 I checked the trans and it was full of gear oil. I immediately changed it back to ATF. A few years ago I had the clutch changed and mechanic who did it said the transmission was noisy so he put the gear oil in. I didn't question this back then.

 

[Gotta_gofast]

What type of noise is it making? Can you describe it in text?

 

[aipaul]

You know after a few days of running the trans with the ATF, the sound is not as loud or I got used to it. I just installed a shift repair kit and it's shifting just great. I may drain and fill the trans again with ATF to clean out any remaining 90w or is having a little 90w in there okay?

 

[Earl43P]

I really don't think whatever residual gear oil remained has any impact.
Not worth replacing x# of quarts of ATF.

 

[rboyer]

I have taken apart many M5OD transmissions which have ran gear oil for a prolonged period of time. I can safely say that it's not a good thing. Just because someone runs gear oil for a year or two and reports back that it did no damage that they know of doesn't mean that it's a good thing to do. Just remember, there are alot of RBV's out there with the original manual trans running Mercon III which have been on the road for almost a couple of decades. How many people out there can say that they ran gear oil in a M5OD for 10-20 years without any issues?