I swapped out my trans fluid for Redline MT-90 last month. One i took the car down and did a little test drive, it was pretty smooth shifting. I drove around for a week with it performing like normal. I went out of town for 2 weeks. Immediately upon return i noticed it was somewhat difficult to go into 1st. It wouldnt go in, and even holding it against the synchros it wouldnt slide in after the 1 sec delay like it used to. Now i have been testing more carefully and it takes a lot more force to downshift into 2nd even only going 20-30mph. It used to be smooth, now its like im fighting with it.
When i changed fluids i did the normal drain, open top, open bottom, let drain for a while, close bottom, new crush washer, put in 2 quarts of Redline mt90, close top w. new crush washer. Ive checked and dont think any is leaking. I did spill some of the old stuff in the parking lot where i did the change, and apparently it eats away asphalt... and i got it all over my hands at the time but i would have noticed it if it were leaking where my car is always parked.

So... Anyone ever heard of this?

 

you are sure it was full?? does it get better after you drive and the tranny fluid warms up?

 

i did the same over summer but mine took 3 quarts.

 

Is this when warmed up or only when cold?

 

try to drive it more like another 2 weeks or so and see if it gets smoother and if not i think something is up with your synchros.

 

MT capacity oil is 1.75L (1.8qt)
Though when I did mine, I managed to get a full 2qts (it was RIGHT at the top of the fill hole).

 

it kind of gets a little easier as it warms up, but still not like stock was.

 

pull the fill plug, make sure it is not over filled. and it is..

let it drain to the proper level. and then get back to us.

beers

 

make sure the car is not jacked up when you let it drain to the proper level...

 

how can i get to the plug if the car isn't jacked up?




also, i asked the question to redline and this was the response i got:

"Paul, thanks for the note and sorry for your problem. We take something like this very seriously and try to help where we can.

We've double-checked all of Mazda's specifications for that transmission, and it asks for a 75W90 GL-4 gear oil. Are you certain that you used MT-90 and not MTL? MT-90 is the correct recommendation for that transmission.

Some transmissions can be very finicky. As you know, MT-90 has a great reputation for a reason--it helps nearly every box in which it is used due to balance friction (rather than being too slippery) and very stable viscosity (to help with both cold and hot shifting). Most of the time, when any gear oil is changed and it you encounter a problem like this, a syncro was already damaged before the oil was changed and a difference in viscosity and friction exposed it.

A good way to figure that out is obviously to put the stock oil back in it and see if it goes back to normal. Autocross and track days are hard on the tranmission. They do get damaged beyond what they oil can mask. It sounds corny, but this box may have developed a bit of its own personality due to hard use and it may just like the stock oil.

I will look around a bit and see if others have had luck with any specific product when a syncro gets sticky like this. I will also contact my friends on the engineering staff at Mazda (they use a lot of our stuff) to see if they have any ideas.

Hope that helps, Cameron"

 

Was the car level, and did you fill it until the stuff was leaking out of the fill hole? If you used MT 90 you used the right stuff, that's what I have, and I actually had a bit of improvement in shifting after I did the swap.

 

Yup, just lower the car to it's normal position while leaving the plug out. If you're on a level surface, then excess should drain out.

 

^ right.

jack the car up,
take a wrench to the plug,
put a fluid catcher below the tranny,
jack the car back down.