So let me start by saying I have searched extensively, and this issue has been covered in general ad nauseam, but I would like to get feedback on this particular issue.

89 GTUs, 127K on the original tranny, newer clutch. Original slave and master cylinder, Mazdatrix shortshifter and new bushings, Redline MT-90 oil put in about a month ago.

I was at Sears Point last month and had a great time on the track. I was driving home after a hard day of shifting, and I hit 5th gear on the highway (never touched it at the track), and all of a sudden it gave a little grinding noise before it went in. First time I have ever experienced this. It kept doing it from then on. If I am really easy on it and shift into gear nice and gently, it will go. The latest development today is that it will not shift at all into 5th, period! I drove in 4th all day today. All other gears work great, no grinding at all, even when I dump it into second. Also, I have tried double clutching, and it still does not work, grinds just the same in 5th.

I know a lot of people will say worn synchros, but do you think maybe I need to replace the clutch slave and master cylinder? I have heard that if these need replacing, they can cause the type of problems I am experiencing. I just recently had the car looked at, and the local wrench did say the slave cylinder needed replacing.

I will be pretty thankful if it turns out to be the master and slave cylinder and not an entire tranny rebuild.

Any advise or similar experiences would be appreciated.

Thanks!

Kurt G.

 

I had the exact same thing happen to mine. It ground slightly shifting into 5th, then after awhile it went out, and had to rebuild the tranny. Sorry, but its probably what you feared, worn synchros.

 

you can try replacing the master and slave cyl...but your 5th gear is probably just going bad...pretty common from what I hear, as is 3rd..

 

my chirps going into 5th. Sometimes it wont go into 5th gear for 2 or 3 days but then it will come back for 2 or 3 months

 

Wierd, I have never had any problems with any FC 5th gears (4 of them). Can you get it into 5th with the car off? It definately sounds like the syncro just die, but all my experiences with syncros going out happened gradually, not in a couple days.

 

You know, when the car is parked and I run through the gears, I always have a bitch of a time getting it into fifth gear. It does not want to go. When I get on the highway, it always (up until now) went into fifth no problem. I have also had the same issues with going into reverse. One day a few months back I could not shift that bastard into reverse for the life of me...I had to push my car out of the parking spot..not cool. Could it be that I am having some kind of issue with my 5th/reverse shift forks? I never had this issue before I got my mazdatrix short shifter. And yes, this problem came out of nowhere. I drove to sears point in the morning with not one issue in 5th gear. I drive the track all day, then get back on the highway to come home, and it is grinding. That seems to me like a shifter or clutch issue, not necessarily a synchros issue, but what the hell do I know...

Kurt G.

 

if it was the clutch slave or master, then it would be worse in the lower gears.

If you drain out the tranny fluid do you have chunks of metal in it? what's the magnetic drain plug look like?

 

Drain plug was normal, just some oily residue, no chunks of metal. I was hoping that MT-90 from Redline would have done the trick, but no dice yet.

Kurt G.

 

Try Redline Shockproof... Altough you should start saving for some new synchros\tranny rebuild

 

Yeah, Super light weight shock proof, not just regular shock proof.

But it sounds like the 5th gear syncro is wasted

 

That is what I was thinking, but was hoping it was something else. Just kinda wierd it showed up out of nowhere. I thought worn synchros gradually made themselves evident.

Kurt G.

 

Yeah, I have only seen them shatter rather than wear out when they are as bad as you suggested, so I expected that you would find metal in the drain.

But there is a problem that I don't think gear oil will solve.