Hey everyone. I have a 2007 Mazda 3, 70K miles. The trany grinds upshifting from 1st to 2nd sometimes but only when im accelarating hard and shift above 3500 RPMs. When i drive the car normally it virtually never grinds. I imagine the synchro is starting to go bad. What I'm wondering is if I will be doing any harm to the rest of the transmission by letting the synchro slowly go bad. Right now its not grinding under normal conditions and the rest of the transmisson/clutch is fine.

I figure I might as well replace the clutch when I eventually have to service the transmission, but I'd like to get some more life out of it. Any thoughts? Thanks.

 

Were I in your shoes I'd try moving to a better gear lube; Red Line is the one I've used in the past to make shifting easier on the syncros.

 

Thanks for the reply. Would a gear lube like red line make it easier for the syncro to shift and do its job, or does it just reduce the grinding noise?

 

It actually makes the job the syncro needs to do easier, so assuming the syncro isn't totally shot, you may be able to get away without ever having to tear the box apart. FWIW, I've been using Red Line gear lube for years and my transmissions always shift smoother after it's put in, especially so in the winter.

 

Great, thanks for the advice. I did some reading and it seems like the Redline is a good idea for my situation. I have a 2007 2.0, any idea on the type of Redline I need? I cant find the specifications for the type of fluid the car takes in the owners manual.

 

Off the top of my head I used something like 75W-90 gear lube.

Edit: http://www.redlineoil.com/Products.aspx?pcid=7

 

Have you ever changed out the transmission fluid in your car? IIRC it's recommended at 60k miles. If nothing else I too would recommend changing out the fluid just to see if you get an improvement. You could pay someone to do a full flush for you, however if you buy a little extra fluid you can do several drain and fills and you'll get most of the old stuff out and that should be good enough.

I have the redline in both of my cars. I really only noticed a slight improvement during cold temperatures in that it loosened up more quickly... it was still a little gummy at first but got better faster.

 

If I'm not mistaken, the OP has a Manual transmission. Assuming I'm correct then there is no service recommendation for changing out the fluid and there is no such a thing as a "flush" available. Yes, no?

 

Thanks for the replies.
Correct, its a manual. So there is no real service schedule. That being said, i had the transmission fluid changed 5-10K miles ago.

I spoke to my local transmission shop. They thought the redline was a good idea and they said they have had some luck using it with bad synchros. It's not a sure fix but its worth trying. Like I said the grinding is only at high rpm's, so i think the synchro is just starting to go bad. Hopefully with the redline I can get some more life out of it. Thanks for the advice.

 

Does double clutching help?