5th gear grinding
 

5 speed Transmission NB1

As I have mentioned in the past, I often skip a gear or two as I'm accelerating. Lately, when I go 2 -> 5 or 3 -> 5 the gear grinds going in, as if the synchronizer is bad. 4 -> 5 never does it.

If I let engine revs come down, it tends not to grind. It does seem that the clutch is fully dis-engaging, however.

Have I ruined the synchronizer for 5th? Bent a Fork? Have a clutch issue? Thoughts?

DNM

5 speed or 6?

5 Speed
 

5 speed. Has 125K miles.

Check clutch pedal adjustment and see if the slave cylinder is leaking before looking further.

Good Points.

Adjustment is good.

Fluid in reservoir is full, but is black. Replaced (trigger warning) Master and Slave 2 years and 25K miles ago. I think I'll pay the big bucks for OEM and replace them for good measure. Track day scheduled for Sept 12. Don't have time to mess around.

DNM

I have rebuilt a lot of these 5-speed Mazda transmissions. Given you replaced the hydraulic components already, and have 125 k on it, I think you have wear on the synchro, and on the sleeve that engages the gear (called clutch sleeve), and possibly the end bearings now have too much play.
If flushing the fluid does not help, then you are looking at a replacement transmission, or refreshing this one.
Perhaps a change in transmission oil could buy you a bit more time, but that is often only worth a few more track days.

I'm going for the the new hydraulics first. If that does not fix it... and I think it will as the issue is intermittent... then I have a spare transmission at the shop.
Fluid in tranny is only 10K or fewer miles. I'll post back results.
DNM

New OEM master and slave from fixed it.

After Six mentioned hydraulics I took notice and realized that the clutch was not consistently engaging at same pedal height. With new hydraulics, same place, near top, where I want it.
DNM

Yay