Ok this is the second transmission I have put in my car. After the engine warms up and is driven for 20-30 min. The transmission gets hard to shift. Now I know what everyone is thinkin...theres the wrong flujid in it. I have tried 80w90. same thing..went to 75w90 synthetic and it helped but it still gets hard to shift when it gets hot. any ideas???
Could the clutch have an effect on the tranny?

 

What do you mean by hard to shift?

Give us some more details. Any noises when its hard to shift?

 

The clutch should not have any effect on shifting since the clutch is disengaged when shifting. It's not touching anything. Does the trans grind when shifting into any gear? You may want to try a mixture of 50/50 automatic transmission fluid and synthetic gear oil. That is supposed to help smooth the shifts.

 

mine did that once after a 30 minute drive. i don't know what caused it.

 

inspect your clutch hydraulic components first. the trans should get eaiser to shift when hot, not harder. i would go through and inspect each component, which will be the clutch master cylinder, the slave cylinder, and hose. inspect each for wear, leaks, and proper function. it may not hurt to rebuild or replace each component while they're out. thoroughly bleed the clutch with the usual dot 3 (i use valvoline syntec). when you replaced the fluid in the trans did you fill the shifter tower to the appropriate level and make sure the shifter was installed correctly around the spring?

 

The tranny does not grind between shifts, no extra noises. when its cold it shifts fine. when you drive it for a little while say 30min or more. between shifts 1-2,2-3,3-4,4-5. it gets harder the longer you drive the car. the clutch stays the same, all fluid is good, full clear. Just the longer you drive the car the harder it is to shift between gears. Idk how else to say it but its weird n buggin me lol. Also when it gets hotter i get a clutch chatter in 1st and reverse. its pretty hard to, it was so bad before i machined the flywheel it chattered the rear u-joint loose. had to change driveshafts. Idk whats up with this car, was great before it sat for 2 yrs...now ive had nothin but problems. idk

 

I have had the same issue with 2 FB transmissions as well, one with 95k, one with 175k. You replaced the fluid, but what brand did you use? I don't think that aftermarket gear oil is as resistant to thermal breakdown as factory Mazda fluid. It is most likely a viscosity issue. My next step is to swap my trans oil for 75w140 Royal Purple to see if this will allow me to have a quiet trans when it gets up to operating temperature.

 

Do you have the heat shields in place, including the windage tray? I does sound like it's clutch hydraulic problem. Once everything heats up, the clutch doesn't fully disengage.

 

I agree with the clutch issue. If your clutch line in still stock, and possibly original it may be heating up softening the rubber so instead of a solid push of the slave, it expands and stretches the rubber line. SS clutch lines are cheap. cheaper than swapping trannys

 

where can you find a ss clutch line?

 

Mazdatrix.com has them for 18 bucks. Ebay has some that seem to work good. Probably not as nice as theres but I think I spent 7 plus shipping or somthing like that. Heres a link for the mazdatrix line

http://www.mazdatrix.com/getprice.asp?partnum=6508

 

I agree with the idea that it could be/is a clutch actuation issue. It could be as simple as air in the system, or just the clutch equivalent of brake fade. I'd swap in a stainless steel line and thoroughly bleed the system and see where that gets you.

 

i ordered a ss clutch line, but i really doubt thats the problem. it is not clutch related, because it is hard to move left and right. i think it has something to do with the shift linkage in the trans. anyone have any idea what keeps the linkage moving smoothly? the only thing i can think of is my trans is low on fluid, or the fluid needs changed. im going to pull the trans in a couple of weeks to change out the clutch and i plan on running mobile synthetic with some lucas in it when i put it back together.

 

You can pull the shifter off and add oil to the shift linkage. that may help some. fill it to the top of the part where the shifter plugs into.

 

wont that just fill the trans? thats how i filled my s10 with trans fluid.

 

i saw in another thread someone said there trans was getting hot because of a missing heat shield. my car has a ghetto custom exhaust the previous owner put on, so im going to look under the car to see if the shield is still there. maybe thats the problem??

 

Could the exhaust heat up the trans that much? I have a full RB exhaust with no heat shields, and I'm grinding 2nd and 4th after driving in town w/o much airflow around the trans.

 

the exhaust gets pretty hot in these cars. i didnt get a chance to look under mine today, but i'm really hoping that the heat shield is the problem.

edit, i just looked and the sheild is there. it looks like it might be leaking out of the trans so its probably low on fluid.

 

If you do this will it hurt the transmission, or blow any seals?

 

Really sounds like a clutch issue to me too. It is the one constant in your car....especially since you seem to be describing the same issue with two different transmissions. And yes....a bad clutch, leaky (internal or external) master/slave cylinder will make shifting hard.

Of course, the other possibility is that you have gotten a hold of two crappy gear boxes. Unless you have opened up the transmissions and inspected the synchro's, gears and bearings you really don't know what you are dealing with.

I have killed several FB boxes in racing. Usually they start grinding on downshifts, next they grind on upshifts and then get hard to shift up or down or just plain won't go into gear at all. When they get to that point they are in need of major repair or replacement.

 

the reason i don't think its the clutch is because its hard to move in neutral, and its only when the car has been driving 55mph+ for more than 30 minutes. when i drive to work i go 55 the whole way, and its pretty warm out. when i get to the gate and down shift, its hard. when i drive home, im not in a hurry so i drive 45-50 and its cool out and when i get home, its not hard. it was consistent for 5 days in a row. i really think its heat related.

 

not on an FB tranny. it has what's considered a remote shifter, so putting oil in at the shifter, that's as far as it will go.

 

no, theres a video of a short shifter install and they tell you to do it. the shifter housing is separate but mounted on top of tranny

 

Sorry to high jack a thread, but how exactly is the shifter supposed to be installed around the spring? I guessed when I installed my short shifter and spread the spring with a flat head skrew driver and put the ball threw it. Hasn't really felt right since. It is really stiff...... Seemed right though???????

 

The tranny shifts fine when cold, especially with the weather temp change where Im at. When it gets hot it does have a clutch chatter in 1st and reverse. When its cold around 50deg for a good half hr 45min I have no clutch chatter, no noises. Nothin but a smooth shifting tranny. Fluid is full and I used valvoline 75w90. I was thinking of using the royal purple 75w90. I have an 03speed protege and I used royal purple twice, and no joke when i put valvoline 75w90 in it the tranny shifted hard, would almost have to double clutch everytime. I dont know why, but when i put royal purple back in I got no problem and smooth shifting. I dont know what goin on with my car but someday I'll figure it out, thanks for all the answers n thoughts n ideas!