I'm looking to change my manual transmission fluid out to try and help my shifting issues with the M5OD. My transmission has a leak from somewhere and I figure maybe enough could've leaked out to cause it to shift rough. I wanted to go with the Syncromesh fluid as that's what's already in it when I bought it and maybe an additive also. I think it takes around 3 quarts of fluid. What brands are good for he Syncromesh and are here any additives you'd use ?

 

The M5OD should have DexIII/Mercon ATF in it, not Syncromesh. It's probably shifting bad because you have the wrong fluid in it.

 

The M5OD is the Mazda trans, correct?

 

The leak is most likely the plugs on the shifter cover. Very common leak area. And just run regular ATF I tried synthetic and it caused shifting issues when trying to shift too fast, I think it was too slick to keep the syncros lined up right.

 

^ this

Mine leaks from poor re-seal between the main case and extension housings

 

Yes, Mazda transmission. I've read on here and a few other places Syncromesh has good results in these transmissions. Mercon is the Ford recommended fluid, not sure which one I should go back to

 

Always use the correct fluid! The engineers didn't spec a certain fluid so you can come along and decide it ain't right!

 

Anything too thick will be a hindrance to the function of this transmission. It works just fine with ATF.
I think many people that try to fix a worn out transmission will use something thicker. If there is nothing wrong with it, use ATF.

 

At 180K this trans is probably just about wore out, but this is my current and only vehicle available to drive right now so it's got to work. I'm going to switch back to ATF, I figure if it is even worse shifting I can just drain it back out and refil the next day. Is there anywhere that sells fluid just specifically as Mercon V?

 

You just need a gallon jug of regular old Dex/Merc ATF. Any auto parts store or walmart will have it.

 

Maybe you could double clutch it like a non-synchro'd trans.

 

I hope not, I've got 250k+ on mine and after getting the synthetic atf out and putting regular atf in its worked fine for the last 100k and expect to get another 100 out of it

 

use what they want from the factory dex/merc. i just drained out my old transmission to put the new 4x4 one in. you fill the trans up till it starts to come out the fill plug. if I'm not mistaken it is about 5qt.

 

Will do, plan to work on the trans tomorrow. Got my door hinge on today but now I think I need a striker and one of the 3 body-to-hinge bolts got a little stripped out so I'll need to remedy that also. Thanks for the help, I'll post up the difference of the transmission feel if there is any

 

I changed the fluid out and back over to Mercon type, the fluid was low previously which I think was having an effect. The gear shifting definitely grabs more and is more notchy, still grinds goin in reverse and first gear is about the same difficulty if not worse to go into. My transmission is turning 35s, I'm not sure if tires have an effect on how long these last. Shifting between gears is smoother besides first and reverse gear which is good.