Gring into 3rd gear only at redline and hard acceleration...why?

[Meeyatch1]

So my 1994 NSX does something odd. Driving around town normally, everything shifts fine. But when I am at a track day or something running flat out, when I go shift into third gear I get a grind at red line. It only does it under those conditions. Does anyone have an idea why?

Again, under normal or otherwise spirited driving, the car shifts fine. But if I am going wide open throttle acceleration and go to shift into third gear at 8,000 RPM, I get a grind unless I shift SLOWLY into gear. All of the other gears are fine.

 

[docjohn]

on upshift and downshift or only one of those?

 

[Meeyatch1]

on upshift and downshift or only one of those?

Upshift only. When I downshift, I almost always blip the throttle, and everything is fine.

 

[RPM217]

My guess is the synchro is begining to go

 

[Meeyatch1]

My guess is the synchro is begining to go

It has been doing it for years, but not during normal driving. It is strange. How can it be diagnosed if the synchro is bad?

 

[docjohn]

are you depressing the clutch fully and giving some fuel at the upshift?

 

[goldNSX]

track = hot gearbox oil
shifting at redline = biggest step for the synchro
question: does it get worse with hotter gearbox oil or how does it behave at the beginning of the track session?
If you don't have a clutch issue the synchro of the 3rd gear is dying on you. I know of one NSX with low but frequent track miles that grinds in 3rd too because of frequent 2nd to 3rd shifts.

 

[jcbadcura]

Unless you want to tear down the trans, I would try a syncromesh fluid change. There are a number of options available (search syncromesh).

It's likely either the syncro going or possibly a bad/chipped 'tooth' in one of the 'cogs' in the trans. I'm not a technician but I've seen it in other cars and this is how it was explained to me.

B&G syncromesh synthetic trans fluid came highly recommended to me by guys that spend time racing nsx's so that's what I put in my Nsx. It's not cheap but like most stuff for this car, you get what you pay for. It wont fix any broken parts but the improved lubrication may improve the issue.

 

[BATMANs]

http://www.nsxprime.com/forum/showthread.php?t=144752

Have u tried running that?

 

[ekhonda87]

Worn synchro is my guess. In my opinion you have 2 options, rebuild the tranny or slow down on your 2nd to 3rd gear shifts so that it doesnt grind. As long you dont keep making it grind, it will likely not get any worse...

 

[Meeyatch1]

are you depressing the clutch fully and giving some fuel at the upshift?

I do not give fuel on upshifts, no.

 

[Meeyatch1]

track = hot gearbox oil
shifting at redline = biggest step for the synchro
question: does it get worse with hotter gearbox oil or how does it behave at the beginning of the track session?
If you don't have a clutch issue the synchro of the 3rd gear is dying on you. I know of one NSX with low but frequent track miles that grinds in 3rd too because of frequent 2nd to 3rd shifts.

It tends to grind on any fast upshifts to 3rd....cold or hot.

 

[Meeyatch1]

Worn synchro is my guess. In my opinion you have 2 options, rebuild the tranny or slow down on your 2nd to 3rd gear shifts so that it doesnt grind. As long you dont keep making it grind, it will likely not get any worse...

I may have to re-build. Because if there is something wrong, I want it fixed.

 

[Stephen@NCAutoUSA]

Don't sweat it Mitch. Enjoy your car and only rebuild if you need too. No use in forking out that kind of cash just yet.

 

[jcbadcura]

I may have to re-build. Because if there is something wrong, I want it fixed.

Seriously, try changing your fluid first.