LSD j30 vs. s14 - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

burgy240 · 02-03-2003, 11:54 AM

Anybody know the benefits and draw backs between a j30 LSD or an s14 stock LSd? I don't mean in terms of install either. I strictly mean regarding performance? thanks, joe

AKADriver · 02-03-2003, 12:00 PM

3.916:1 gear ratio instead of 4.083:1.

4% loss in mechanical advantage... 4% worse acceleration.

Aside from the gear ratio it should be exactly the same (same LSD response).

HippoSleek · 02-03-2003, 12:19 PM

Seeing as you have an SR, you might consider it more like 4% more gear in every gear. I know a fast SR w/ a typical KA final drive sucks.

Ryan will correct me if I'm wrong, but I think the j30 is the same ratio as the SR.

AKADriver · 02-03-2003, 01:11 PM

5-speed SR cars had the 4.083:1 ratio, same as the KA.

The extra speed in each gear might be worth it if you're frying the tires off the line right now.

RedSuns · 02-03-2003, 03:58 PM

so explain why my 1997 J30t rear end had 4.08 stamped into the RING gear......i have been asking about this for a long time

HippoSleek · 02-03-2003, 07:47 PM

Why. Why. Why. I never get this one right. I distinctly remember telling someone the USDM and JDM lsd's were the same... and was promptly pointed to heavythrottle saying they weren't. I backed up the search on FA and agreed w/ heavythrottle. Since the search is broken and Jeff and Yury don't have any diffs on their site, I can't refute this. Ugh.

whateverjames · 02-03-2003, 09:09 PM

didn't different years of the j30 have different gears? like a 95 had a 3.916:1 gear ratio?

drift freaq · 02-04-2003, 01:48 AM

ok guys most if not all J30's came with 3.916 which rounds off to 3.92 gears . I have never heard or seen a J30 diff with 4.08 .
Ok now on to the Japanese side of things . CA18 powered cars supposedly came with lower gears than are in our cars here stateside.
NA SR cars came with 4.08 . S14 SRdet cars and S15 SRDET cars came with 3.70 gears just like the Z32 VG30DETT cars. I know this because I was researching it about a year ago. Now on the S13's it seems that some SRDET cars did come with 4.08's but there where also some that came with 3.70 gears. I think it all depended on the year.
FWIW if you are running a SR you are better off with a 3.92 or 3.70 gear rear end because it will indeed keep you in boost longer due to the fact that it takes a bit longer to rev through your gears.
Which means that though its taller you will still pick up acceleration due to being under boost longer.
this is why a NA Z32 diff has 4.08 gears like our car and the Z32 Turbo diff has 3.70 .

AKADriver · 02-04-2003, 07:56 AM

On all the S13 and S14 5-speed SR20DET clips I've ever seen, the axle code listed on the firewall tag was "RC40" indicating a ~4.0:1 R200.

Nissan axle codes:
R = RWD
A = R160, B = R180, C = R200, D = R230
## = ratio rounded to the nearest tenth

If you're pulling a diff from a J30 and you're unsure of the ratio, RC39 will be the 3.916:1 box, RC40 will be the 4.083:1 box.

Automatic S13/S14 SR20DETs had the 3.916 ratio.

The 3.692:1 ratio was included with the six speed in the S15.

Here's some proof:

I could find more... anyway, find a shot of an S13 or S14 firewall tag indicating an SR20DET, a manual transmission (FS5W71C), and an axle other than 'RC40', and I'll believe it.

- Ryan, FIREWALL TAG NAZI!

Edit: just an aside... the CA18DET ratio was indeed 4.363:1, manual or automatic. Their tags say 'RC43'.

HippoSleek · 02-04-2003, 09:35 AM

ATTN MODS - can someone change this guy's status to "Firewall Tag Nazi"? That would own.

Okay, my problem is that I am now having a fundamental issue with multiple information sources. Your info is always good and firewall tags are awfully tough to refute BUT, so is heavythrottle.

Query: did the SR20DET auto come with a 3.9 or 3.7 ratio?

Query2: why can't the Japanese round numbers like the rest of the world?

AKADriver · 02-04-2003, 10:25 AM

Q1: 3.916 by every source I've seen.

Q2: I guess it's really truncated more than rounded... going to four digits is just my own pedantic self

Steeles · 02-04-2003, 11:13 AM

Quote:

Originally posted by AKADriver

Edit: just an aside... the CA18DET ratio was indeed 4.363:1, manual or automatic. Their tags say 'RC43'.

hehehe thats whats under my S14 now! well equipped with a NISMO LSD

let me tell you... 1st gear? its useless

RedSuns · 02-04-2003, 02:05 PM

i am betting that the junkyard mis-labeled it......because i have been cloked at 85 and my speedo was dead on......

burgy240 · 02-05-2003, 11:33 AM

So the final decision is that it is better for me to go with the j30 for my SR powered s14 right? I belive that this is the way I will go after all unless someone can prove the other case. thanks all.

AKADriver · 02-05-2003, 01:10 PM

There's no proof one way or the other, it's all preference and what you plan to use the car for.

02-03-2003, 11:54 AM	#1
burgy240 Nissanaholic! Join Date: Oct 2001 Location: Tampa Age: 49 Posts: 2,151 Trader Rating: (2) Feedback Score: 2 reviews	LSD j30 vs. s14 Anybody know the benefits and draw backs between a j30 LSD or an s14 stock LSd? I don't mean in terms of install either. I strictly mean regarding performance? thanks, joe __________________

02-03-2003, 03:58 PM	#5
RedSuns Nissanaholic! Join Date: Jan 2002 Location: Northern VA Age: 43 Posts: 1,865 Trader Rating: (1) Feedback Score: 1 reviews	so explain why my 1997 J30t rear end had 4.08 stamped into the RING gear......i have been asking about this for a long time __________________ Johnathan 2005 Titan 1996 240SX 1991 240SX 1974 260Z 1996 Honda CBR 600 F3

02-03-2003, 07:47 PM	#6
HippoSleek Nissanaholic! Join Date: Aug 2001 Location: elsewhere Posts: 2,081 Trader Rating: (0) Feedback Score: 0 reviews	DOH Why. Why. Why. I never get this one right. I distinctly remember telling someone the USDM and JDM lsd's were the same... and was promptly pointed to heavythrottle saying they weren't. I backed up the search on FA and agreed w/ heavythrottle. Since the search is broken and Jeff and Yury don't have any diffs on their site, I can't refute this. Ugh.

02-03-2003, 09:09 PM	#7
whateverjames Nissanaholic! Join Date: Jul 2001 Location: St. Louis Age: 45 Posts: 2,263 Trader Rating: (0) Feedback Score: 0 reviews	didn't different years of the j30 have different gears? like a 95 had a 3.916:1 gear ratio? __________________ 02 Blazer X - 90 240SX w/SR oh noes

02-04-2003, 01:48 AM	#8
drift freaq R.I.P. Aya, always love Join Date: Nov 2001 Location: Los Feliz/Hollywood Posts: 18,564 Trader Rating: (215) Rides Gallery: drift freaq Feedback Score: 215 reviews	ok guys most if not all J30's came with 3.916 which rounds off to 3.92 gears . I have never heard or seen a J30 diff with 4.08 . Ok now on to the Japanese side of things . CA18 powered cars supposedly came with lower gears than are in our cars here stateside. NA SR cars came with 4.08 . S14 SRdet cars and S15 SRDET cars came with 3.70 gears just like the Z32 VG30DETT cars. I know this because I was researching it about a year ago. Now on the S13's it seems that some SRDET cars did come with 4.08's but there where also some that came with 3.70 gears. I think it all depended on the year. FWIW if you are running a SR you are better off with a 3.92 or 3.70 gear rear end because it will indeed keep you in boost longer due to the fact that it takes a bit longer to rev through your gears. Which means that though its taller you will still pick up acceleration due to being under boost longer. this is why a NA Z32 diff has 4.08 gears like our car and the Z32 Turbo diff has 3.70 . __________________ "Having a lot of tracks on a song is like putting stickers on a car to get more horsepower" New Video https://www.youtube.com/watch?v=uebV1OnbRsw Buy my mounts! http://zilvia.net/f/sale-items/51531...ns-mounts.html http://zilvia.net/f/tech-talk/317539...e-mouts-6.html

02-03-2003, 12:00 PM	#2
AKADriver Post Whore! Join Date: May 2002 Location: Springfield, VA Age: 43 Posts: 3,517 Trader Rating: (1) Feedback Score: 1 reviews	3.916:1 gear ratio instead of 4.083:1. 4% loss in mechanical advantage... 4% worse acceleration. Aside from the gear ratio it should be exactly the same (same LSD response).

02-03-2003, 12:19 PM	#3
HippoSleek Nissanaholic! Join Date: Aug 2001 Location: elsewhere Posts: 2,081 Trader Rating: (0) Feedback Score: 0 reviews	Seeing as you have an SR, you might consider it more like 4% more gear in every gear. I know a fast SR w/ a typical KA final drive sucks. Ryan will correct me if I'm wrong, but I think the j30 is the same ratio as the SR.

02-03-2003, 01:11 PM	#4
AKADriver Post Whore! Join Date: May 2002 Location: Springfield, VA Age: 43 Posts: 3,517 Trader Rating: (1) Feedback Score: 1 reviews	5-speed SR cars had the 4.083:1 ratio, same as the KA. The extra speed in each gear might be worth it if you're frying the tires off the line right now.

02-04-2003, 07:56 AM	#9
AKADriver Post Whore! Join Date: May 2002 Location: Springfield, VA Age: 43 Posts: 3,517 Trader Rating: (1) Feedback Score: 1 reviews	On all the S13 and S14 5-speed SR20DET clips I've ever seen, the axle code listed on the firewall tag was "RC40" indicating a ~4.0:1 R200. Nissan axle codes: R = RWD A = R160, B = R180, C = R200, D = R230 ## = ratio rounded to the nearest tenth If you're pulling a diff from a J30 and you're unsure of the ratio, RC39 will be the 3.916:1 box, RC40 will be the 4.083:1 box. Automatic S13/S14 SR20DETs had the 3.916 ratio. The 3.692:1 ratio was included with the six speed in the S15. Here's some proof: I could find more... anyway, find a shot of an S13 or S14 firewall tag indicating an SR20DET, a manual transmission (FS5W71C), and an axle other than 'RC40', and I'll believe it. - Ryan, FIREWALL TAG NAZI! Edit: just an aside... the CA18DET ratio was indeed 4.363:1, manual or automatic. Their tags say 'RC43'. Last edited by AKADriver; 02-04-2003 at 07:59 AM..

02-04-2003, 09:35 AM	#10
HippoSleek Nissanaholic! Join Date: Aug 2001 Location: elsewhere Posts: 2,081 Trader Rating: (0) Feedback Score: 0 reviews	ATTN MODS - can someone change this guy's status to "Firewall Tag Nazi"? That would own. Okay, my problem is that I am now having a fundamental issue with multiple information sources. Your info is always good and firewall tags are awfully tough to refute BUT, so is heavythrottle. Query: did the SR20DET auto come with a 3.9 or 3.7 ratio? Query2: why can't the Japanese round numbers like the rest of the world?

02-04-2003, 10:25 AM	#11
AKADriver Post Whore! Join Date: May 2002 Location: Springfield, VA Age: 43 Posts: 3,517 Trader Rating: (1) Feedback Score: 1 reviews	Q1: 3.916 by every source I've seen. Q2: I guess it's really truncated more than rounded... going to four digits is just my own pedantic self

02-04-2003, 02:05 PM	#13
RedSuns Nissanaholic! Join Date: Jan 2002 Location: Northern VA Age: 43 Posts: 1,865 Trader Rating: (1) Feedback Score: 1 reviews	i am betting that the junkyard mis-labeled it......because i have been cloked at 85 and my speedo was dead on...... __________________ Johnathan 2005 Titan 1996 240SX 1991 240SX 1974 260Z 1996 Honda CBR 600 F3

02-05-2003, 11:33 AM	#14
burgy240 Nissanaholic! Join Date: Oct 2001 Location: Tampa Age: 49 Posts: 2,151 Trader Rating: (2) Feedback Score: 2 reviews	So the final decision is that it is better for me to go with the j30 for my SR powered s14 right? I belive that this is the way I will go after all unless someone can prove the other case. thanks all. __________________

02-05-2003, 01:10 PM	#15
AKADriver Post Whore! Join Date: May 2002 Location: Springfield, VA Age: 43 Posts: 3,517 Trader Rating: (1) Feedback Score: 1 reviews	There's no proof one way or the other, it's all preference and what you plan to use the car for.