I'm not exactly sure what type of gear oil to run in my M5OD. I know not to use GL-5, but is it safe to use Gl-4? Or do I need to run even less? I know the GL ratings are the amount of friction modifiers...and Gl-5 will be hell for my transmission to shift with. I just don't know which rating to use for best results.

 

Id say gear lube is not good to put in the Mazda M5OD since it specs ATF. I ran Mobil 1 ATF in mine for 40,000 miles, but recently switched to Redline D4 ATF which is GL-4 rated, but specifically states it is compatible with yellow metal so it won't tear up the syncros. Some recommend the Redline MTL which is like the D4 but thicker. There is some discussion of the Redline in the M50D here, including my experience:
https://www.ford-trucks.com/forums/s...8&page=1&pp=20

 

I've used Shell or Advance Auto house brand Mercon rated ATF every change. 131,000 miles, and so far, so good.
From all I have read, there ain't much you can do to smooth up the annoying M5OD.

 

Never use Gear oil in a Mazda 5 speed! Use only ATF.

I'm disappointed to hear that the D4 ATF does not make much of a difference in the transmission.

 

While I use ATF in my 2002 F-150 Manual tranny I would really love to know why gear oil is "foreboden" . I've heard that gear oil can't lubricate properly in a manual tranny that requires ATF. My stinky Ford tranny in my 2002 F-150 seems to be really junky with ATF. Even with the good stuff! I use Schaeffers #204S Semi synthetic Dexron III/Mercon. It helped tremendously with shifting quality but it still grinds occasionally. But winter driving is 100% better . So why is gear oil bad for these tranny's?

Whimsey

 

The problem is the flow properties are very different. Whereas ATF will flow like water when it's warm and almost like water when it's cold, the gear oil is very slow to flow. Most ATF trannies depend on splash lubrication for some of the gears, whereas they have baffles and troughs to route the oil to the gear. When using gear oil, some gears can be starved for oil, and burn up. Aside from that, I think it screws the synchro's.

 

Keep in mind my comparison was to the Mobil 1 ATF I had been running and my tranny likely was abused based on buying the truck at 58,000 miles and having the clutch and rear pinion go on it. Clutch was very abused. There were mounting holes for a hitch on the frame too. I think they pulled grossly overloaded trailers with it.

Perhaps the thicker Redline MTL would work better, but I didn't go with it because of the stories of burned up M5OD gears from too thick an oil.

BTW: Someone on FTE once posted about putting a B&M shifter in their M5OD and said it shifted a lot better.

 

I might try the Redline D4 ATF because any improvement would be worth the slight cost. You probably noticed less of a dramatic difference by comparing it with Mobil 1.

I have seen first hand what can happen to one of these 5 speeds when you run gear oil. The front gears literally melted and many others were bluish tinted.

I was under the impression that Hurst made the shifter for the Mazda 5 speed.

 

You are right. It had to be a Hurst.

 

I was under the impression that the gear oil helped out worn synchro's, rather then hurting them.

So I guess that when I change my drain plugs (My truck marks her spot after driving ^_^) I should fill it up with Redline D4 that is rated to work with the 'yellow' synchro's this thing has. Thanks for letting me know that.

What about the gear oil that is already in the transmission. Putting in ATF there's still gonna be that residue of gear oil?

How long would the fluid last? Will it have to be changed every 30,000 miles like a manual, or no?

About those damn drain plugs - is it possible to replace them by hand from underneath, or do I HAVE to remove the shifter assembly and floor pan, all of that stuff? Anybody know the cost for metal replacements?

 

Syncros need friction to operate correctly. Not sure what can help worn syncros. Redline D4 ATF is about 7.5 cSt at 100C (like a 0w20 motor oil). Redline MTL is around 10.6 cSt (like a 5w20 motor oil) and MT-90 is around 15.6 cSt (like a 15w40 motor oil). The MTL might be fine in the M5OD. In fact I am sure it would work. Redline's tech only said it would make cold weather shifting stiffer, but he kept turning me back to the D4. Both D4 and MTL are in the 70w80 gear oil weight, whereas the MT-90 is a 75w90 gear weight.

Read the brochure on MTL at the Redline site. It talks about the compatability with the yello metal.

Residue of the previous fill should not be a problem as the Redline is compatible. The residue should mix in with negligible effect on overall oil weight.

I would think the Redline should last a lot longer than conventional ATF and probably a bit longer than Mobil 1. I am thinking 60,000 miles (I was runing the Mobil 1 30,000), but you could ask the tech at Redline.

I finally located the drain plugs (mine are nice and dry) and am not sure how they come out. Maybe just pry out. Looks like you could do it by just crawling under the truck and getting yourself somewhat in a contorted position for a while.

BTW, I am no expert. Just read everything on the Redline site.

Also, I used a tip I found on this site to get a clear plastic tube and stick one end in the tranny fill hole and the other in the engine bay with a funnel. Then pour from the under the hood. Worked great for me as with the I6 I could actually see it going in the tranny fill hole. Also, this tranny slopes and I had to jack the filler side of the truck up to get the full 3.8 qts in.

 

I was under the impression that changing the transmission fluid was either 50,000 or 100,000 in my ranger.

I replaced my shift rail plugs when I removed the transmission to replace the slave cylinder. I replaced them with steel cup plugs for less than $5.

I'm going to buy some Redline D4 ATF next time I order from Jegs and I will let you all know how it works.

 

So in changing your plugs...do you know if there is clearence to get them changed with the transmission inside the truck still? I don't want to dig up my floor pans and carpet and all that if I can, with some difficulty expected, get the plugs out from underneath reaching over.

The plug on the side of the transmission is the fill plug...so..fluid only has to be that high in order for the tranny to work? Seems kinda empty to me.

 

You can get the rubber plugs out without a problemfrom the underside. I don’t think there is clearance on a Ranger to knock the metal plugs in but there might be on a 150. A fresh set of rubber plugs will work for a long time if you can’t get the room to swing a hammer.

Yup, drain it and fill it up to the bottom of the fill hole. The 3.5 quarts or so that are in the bottom are splashed and channeled to keep the upper parts lubed.

TallPaul: What did you pay for that D4?

 

The D4 cost me $7.95 per quart and about as much for shipping direct from Redline.



WHOOPS , that should say 10.6 cSt (like a 5w30 motor oil).