The car has 90k miles, clutch/flywheel/fluid been replaced couple years ago at about 85k miles. Just recently shifting from 4th to 5th it grinds. If the car is stop and clutch in, all gear shifts are fine. It only happens when the car is in motion/accelerating. If I let the rpm drops a little (putting the car in neutral for a second while the car is in motion), the grind is less, almost none.

Could this be a engine/tranny mounts gone bad? or am I looking at a big ticket item like tranny/gear replacement?

The car is a 2006, so it should have the CD009 tranny.

I take the car to tracks and do HPDE, other than that the car sits in garage most of the year. On average, the car gets to see daylights about 5 weekends/year.

The fluid that was put in when installing the clutch/flywheel was Redline MT-90 (redline for sure)? clutch/flywheel combo was the Z1 combo. Work was done at a trusted local dealership.

Thanks for all your help!

 

Isn't this how you're supposed to upshift?

 

No, you don't always rpm match on an upshift. A quicker shift is why the syncros are there.

Your syncro is going bad, just rpm match it and deal with it.

 

If you rev match, its smoother and easier on the tranny. Everyone knows powershifting is harsh on tranny, speed shifting is the same. For daily, idk why people wont spend the extra .5 sec to rev match

 

No...... what I meant to describe is from 4th to neutral, pause (like a long pause), then slowly go into 5th.

fwiw, I don't powershift, and I wouldn't call my shifting as "speed shifting" neither, it's not like I just jam it in in 0.3s like in movies or what not. I shift just like any normal people do: clutch in, move the shifter, clutch out.... all that done in about 1-2seconds? I'm describing how I upshift, downshift I do rev match. Speaking of downshift, I never tested from 6th to 5th to see if there's the same grind. My car aint got that much power on the straights where I need to use my 6th at the track. So the problem only occurs on upshift, from 4th to 5th. I don't daily my car.

So what you implying is that it's not repairable? or too expensive for repair? If I were to repair it, my choices are either replace the tranny or replace the syncros?

 

Is this your first manual transmission vehicle? Noob.

 

Rev matching works both ways, upshifting and down shifting.

 

I had similar issues going from 1-2, 6-5 and sometimes R.
So for a while I would go something like:
1-N-2
6-N-5
I still do this sometimes when warming the car up.

I use Nissan transmission oil, nobody else and iirc some molyslip in there too.

However now the car feels amazing after doing these, and no problems:
Torque solutions poly transmission mount (Hard Race rubber might be better for daily)
Whilteline diff mounts
Vibra-technics 'road' engine mounts

 

Never put moly in a gearbox, as it makes the synchro's too slippery, and they need the proper amount of friction to operate properly. This is also an issue with synth oils not specifically made for gearboxes.

 

Yeah, first thing first I guess. going to pick up some OEM tranny fluid and switch it back to oem. The oem fluid lasted me 85k and never had any problems. I can't say this is caused by the Redline oil, but after I went with it, the shifting became notchy at cold. Once warmed up it's fine..... til now with the 5th grind.

 

It was changed a few years ago and I'm not sure if they used it or not, wasn't myself (diff and box oil due to be done soon anyway ).

However, to the OP - consider what I said.
It made a gigantic difference to my shift feel and gear selection.

 

thanks Rob. the tranny and engine mounts are definitely on my next to-do list if changing fluid doesn't solve my problem.

 

Although my car is primarily set up for road driving (with hopefully a handful of track time), it's on poly mounts for driveline stuff, and SPL for bushings (and various suspension components) - so it's not cossetting but not totally harsh either. The extra bit of rumble from the trans mount doesn't bother me as it's not driven for commuting journeys