Hi, hope the question hasn't been asked before. I searched, and I could only find information about grinding. Thats not what I have. It's a rattling metallic noise. very faint. Seems to only happen in 2nd gear though. I made a short video for YouTube showing the problem so you can listen for yourself. No other issues.

https://www.youtube.com/watch?v=smaK...ature=youtu.be

Again, I do apologize if someone asked about it before. Not trying to upset any of the members here.

 

Tell us about the car..

Engine, Year, Transmission, Mods?

 

It's a 2004 RX8, 65,000 miles, 6 speed manual gearbox, original engine. All recalls done, run on 93 octane fuel, engine oil changed every 3,000 miles.

 

I could not hear it in the video, maybe old ears. Is the clutch the original clutch?

When were trans and diff fluids changed? Might want to look to that. A second gear specific noise, that goes away when you press the clutch, may be related to second gear. I get a rattle around 2K, but that is in all gears and because of my light flywheel.

 

You can hear it better if you skip to 0:25. It almost sounds like a computer's hard drive rattle/chatter.

I'm not sure when the transmission fluid and differential fluid were last changed, but I'll be finding out tomorrow and I'll change it anyways.

 

If the sound is specific to 2nd gear you might wanna check your rubber insulator boot. I had that noise on mine. Found out that the boot was torn in a few places which lets all the sound into the cabin. Replaced it and the problem was gone. Transmission chatter is pretty common and normal on 8s, of course depending on how severe it is and the drive-ability.

 

How do I go about checking that rubber boot?

 

unscrew the shifter **** and remove the plate that the shifter boot is attached to. its directly under there

 

Checkout this video. Its actually for radio removal but is good for the purpose of getting to the boot. Let us know if that resolved your issue.

 

Well I changed the differential fluid to RedLine 75W-90 GL5 oil, and the transmission oil to MT-90.

The transmission seems to have difficulty going into certain gears randomly. Sometimes it's smooth, authorities it isn't. I actually got a grind going from 1st into 2nd, but that was once, and it's fine now... Although I'll update this post after I go for another drive tonight.

The tranny was fine until I changed it's fluid, but I thought MT-90 was the stuff to use. After doing some research, if seems like perhaps I should have chosen Amsoil
Manual Transmission & Transaxle Gear Lube 75W-90. But I hear that Miata owners (who supposedly have very similar transmissions) have good luck with Ford's Motorcraft XT-M5-QS a.k.a Motorcraft MTX-75.

Any suggestions?

 

I recently got MT-90 into Transmission and 75W90 into the Diff. My changes are smooth even when it's around 0 degree up here in Canada. I have slight whirring in 2nd and neutral which is normal according my research. I believe Redline is good stuff.
Are you sure you didn't swap those fluids ?