I posted this question on the oil&lube forum also, but seeing as how I'm home sick with the flu, and bored,I'll ask here.In the oil&lube forum, there are many opinions as to what oil/fluid to use in the m50d manual tranny.Some say ATF, some say 10w30/5w30. I say, if motor type oil can be used, then why not motorcycle oils. They lube the engine, as well as the gears in the tranny, so I know it will have good "shear" properties. If this is madness, just say so, I can take it (Brian ) . Maybe a guinea pig, any volunteers....not everyone at once.

 

Thomas,
Nah, don't think it's madness to consider.
I do wonder what the objective is, for those who try different tranny fluids.
I don't think it is longer life - I don't hear of many M5OD transmission eating up gears. So I guess it is smoother shifting. But, it seems no matter what guys use these do not become slick shifting, short throw gear boxes.
As you probably know, I have always used any old Mercon ATF. Whatever is on sale, house brand, etc.
I change it every 30-40K miles. This has served me well.
I have read enough about the confilict between motor oil and brass and/or bronze metal in the tranny, but I do not know this as fact. I have chosen not to be atest bed for validation!
Sticking to my "if it ain't broke, don't fix it." philosophy, I stay with the Mercon ATF.

 

Your right Brian, it's primarily for smoothness. I have tried many types of atf, but it still seems the same. Did you notice on the oil&lube forum where several had stated that Mazda actually recommends fluids other than atf? They have yet to post any proof. Not saying it's not true, but I like to have a little more data than " I heard" or "they say" before I mess with my primary means of transportation. With 158,000+ in 3yrs and one month, my tranny is no smoother today than when new, and if it went out tomorrow, I couldn't really complain. If nothing else, maybe it'll start some digging, 'cause as you know, we have some very resourceful folks in this forum. Ultimately, I like you, couldn't recommend anything other than what I've been doing. Maybe while I'm laid low, I'll dig a little myself.

 

Dig a little and let me know what you find!

Smart move on applying a little common sense filtering to "what they say". I wonder if the lube can have a significant impact on the synchros moving - at least enough to really make a big difference. I just accept the M5OD as being a little "clunky". Maybe some are worse than others. I can't speed shift, and sometimes low gear is a pain to get in, but all-in-all, I can't complain.

I see it this way: I paid $16,500 for the truck brand new 5 years ago. When I look at the service this truck has provided and the total cost of maintenance and repairs, it has been a bargain.
Now, If I had spent $36,500 for the truck brand new, I'd likely be a little less tolerant of a clunky 5-speed!

I'm guessing you and I hold similar views on this subject.
BTW - I think I'll roll over 160,000 this week. You have caught me!

Take care and get well.

 

i've heard a good tranny fill is this:

3 quarts: mobil 1 ATF
1 quart : lucas

i have no idea what lucas is, but when i do my tranny flush, i'll be using it!

 

Again, who claims this? where is the proof? Lucas is just an additive that basically makes whatever you add it to thicker(higher viscoscity) and "tackier" . I have spent 2 days online, searching for answers. Apparently, the main reason for atf being used, is smoother shifting at low temps. Also, the thinner fluid gets into tighter areas quicker. I found some info,I believe it was a link off of bobistheoilguy's page.ATF viscoscity @100deg celcius

=8 cst (centistokes)
5w30=11 cst
10w30=11cst
10w40=15cst
10w50=19

In light of this, a 5w20-30 oil would be fine in terms of thickness, for me anyway, 'cause I live in relative mild climate.The big factor will be the extreme pressure (EP) additives, usually sulphur and/or phosphorous. Too much of either, will degrade the bronze in the synchros. If the motorcycle oils do not have too much EP additives, then I believe that a 10w30 synthetic would be perfectly acceptable. In lieu of this however, Redline MTL seems to be the best compromise I have found so far. It's thicker than regular atf, hopefully smoothing up the shifts, but thinner and has less EP additives than a multi weight gear oil. I plan on trying one or the other on my next tranny fluid change. Again, I must stress that this is only for manual trannys, auto owners should use only exactly what the manufacturer recommends, and nothing else!

 

This is where I go for lube info, This site will will hook you. It has just about anything to do with lubricants. bobistheoilguy.com you will have to type it in manually.
Then click on forums on the left about half way down.

Mark