Gearing noise on 4th gear deceleration ( No throttle) - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

2slow2go · 06-06-2016, 10:17 AM

So i just got an sr20det 240sx and i was driving home and i hear a 4th/3rd gear grinding noise from the transmission tunnel area. It only happens when i cruising off the throttle in the gear in specifically those gears.

Any ideas?

e1_griego · 06-06-2016, 10:27 AM

Presumably the car has an aftermarket clutch?

It's probably just drivetrain harmonics coupled with stiffer-than-stock mounts.

jedi03 · 06-06-2016, 10:41 AM

could be worn bearings...change gear oil and will tell you...could just be bad harmonics too tho...the tranny is close to you and not very well insulated for noise...

2slow2go · 06-06-2016, 10:43 AM

yeah aftermarket clutch i believe. I've read online and they say it could be harmonics and maybe the frequency of the diff and tranny together or syncro bad or aftermarket setup. Another said it might be the bearings like the input but i dont see any sound diff in neutral when i push the clutch in and out.

At first I thought it might be an unbalanced driveline but that would mean it would make noise at accel and decel.

It also odd that it mainly does it in 4th gear.

Haven't saw you forever E1_griego. NWN is dead..

e1_griego · 06-06-2016, 10:50 AM

Yup, 100% dead. I even deleted the NWN link from my bookmarks bar since it wasn't worth going any more.

4th gear is 1:1 ratio so that's why it's the noisiest. All my 240s have done it. Scary at first, but years and years later it's just the cost of doing business with aftermarket parts.

Def · 06-16-2016, 05:20 AM

Yep, it's diff harmonics due to the 1:1 ratio of 4th. It's loudest at about 2.5-3k RPM or so.

A stock clutch disc will have almost zero noise in this situation.

canadians14sr20det · 06-16-2016, 09:52 AM

Backlash in the transmission in 4th coupled with a worn input shaft bearing makes this noise.

It's annoying, but won't hurt anything. Every used transmission I've owned for my SR makes that noise. The noise never killed a single one of them.

06-06-2016, 10:17 AM	#1
2slow2go Zilvia Addict Join Date: Sep 2006 Location: Bothell Age: 79 Posts: 622 Trader Rating: (7) Feedback Score: 7 reviews	Gearing noise on 4th gear deceleration ( No throttle) So i just got an sr20det 240sx and i was driving home and i hear a 4th/3rd gear grinding noise from the transmission tunnel area. It only happens when i cruising off the throttle in the gear in specifically those gears. Any ideas? Last edited by 2slow2go; 06-06-2016 at 10:47 AM..

06-16-2016, 05:20 AM	#6
Def Post Whore! Join Date: Apr 2004 Location: Houston, TX Posts: 2,701 Trader Rating: (16) Feedback Score: 16 reviews	Yep, it's diff harmonics due to the 1:1 ratio of 4th. It's loudest at about 2.5-3k RPM or so. A stock clutch disc will have almost zero noise in this situation. __________________ S13 Hatch - Goes around tracks quickly DEFSPORT

06-06-2016, 10:27 AM	#2
e1_griego Post Whore! Join Date: Sep 2004 Location: Independence, Ore. Age: 40 Posts: 2,722 Trader Rating: (24) Feedback Score: 24 reviews	Presumably the car has an aftermarket clutch? It's probably just drivetrain harmonics coupled with stiffer-than-stock mounts.

06-06-2016, 10:41 AM	#3
jedi03 Nissanaholic! Join Date: Jul 2008 Location: albuquerque Posts: 1,842 Trader Rating: (8) Feedback Score: 8 reviews	could be worn bearings...change gear oil and will tell you...could just be bad harmonics too tho...the tranny is close to you and not very well insulated for noise...

06-06-2016, 10:43 AM	#4
2slow2go Zilvia Addict Join Date: Sep 2006 Location: Bothell Age: 79 Posts: 622 Trader Rating: (7) Feedback Score: 7 reviews	yeah aftermarket clutch i believe. I've read online and they say it could be harmonics and maybe the frequency of the diff and tranny together or syncro bad or aftermarket setup. Another said it might be the bearings like the input but i dont see any sound diff in neutral when i push the clutch in and out. At first I thought it might be an unbalanced driveline but that would mean it would make noise at accel and decel. It also odd that it mainly does it in 4th gear. Haven't saw you forever E1_griego. NWN is dead..

06-06-2016, 10:50 AM	#5
e1_griego Post Whore! Join Date: Sep 2004 Location: Independence, Ore. Age: 40 Posts: 2,722 Trader Rating: (24) Feedback Score: 24 reviews	Yup, 100% dead. I even deleted the NWN link from my bookmarks bar since it wasn't worth going any more. 4th gear is 1:1 ratio so that's why it's the noisiest. All my 240s have done it. Scary at first, but years and years later it's just the cost of doing business with aftermarket parts.

06-16-2016, 09:52 AM	#7
canadians14sr20det Join Date: Oct 2011 Location: Canada Posts: 43 Trader Rating: (0) Feedback Score: 0 reviews	Backlash in the transmission in 4th coupled with a worn input shaft bearing makes this noise. It's annoying, but won't hurt anything. Every used transmission I've owned for my SR makes that noise. The noise never killed a single one of them.