Gear ratio question?

All about KA-T Drag Racing. Bragging, Timeslips, Results, Questions, Whatever
Post Reply
Badazzsr20
240sx Wannabe
Posts: 140
Joined: Wed Sep 09, 2009 8:35 pm

Gear ratio question?

Post by Badazzsr20 » Tue Aug 26, 2014 9:36 pm

Hey guys I have a question. I was wondering lets say we have a 240 with a 1jz r154 and let's say we have it making 550rwhp. With a 4.11 300z diff in the rear the car ran perfect at the track it was a perfect set up and going throw the traps at about 6k 6.5k for say.

Now here's the question?

Let's say we have that same 240 now making 700rwhp my question is will that same diff gear ratio Help or hurt the car in proformance? How much rwhp would a car need to make to get that 3.69 gear ratio to help the car rather then hurt the car?

Will 700rwhp be enough to make that 3.69 gear wind out like that 550rwhp 240 with a 300z 4.11 gear ratio?

If the gear ratio of 3.69 with 700rwhp help please explain how it will and what are the benefits.

This question is to help a few friends out cause we all have diffrent out looks. If the 240 with 700rwhp is not benifishial how much rwhp would one need for the 3.69 to be working at optimal proformance?

Also would like to know this if a 240 with 700rwhp let's say traps 140 at the track with a 4.11 gear ratio and if u swap out the 3.69 gear ratio will the trap speed go up to let's say 145 or will the car lose trap speed? I guess this question can be answered with the 3.69gearratio question of being benifital.

There's a few questions here if u can please try to answer them all that would be great sorry if I was hard to understand. I'm trying to explain this the best I can.

Thanks guys!!!!

RosadoRacing
Dont Question My Nissan Knowledge
Posts: 540
Joined: Tue Apr 06, 2010 5:33 pm
Location: Bethlehem, PA
Contact:

Re: Gear ratio question?

Post by RosadoRacing » Sat Aug 30, 2014 2:35 pm

My car has 700whp with 26" tires I hit redline at 1000ft around 145mph 7500rpm with the 4.08. So I went with a 3.92 rear and will try the car out next weekend. A 3.69 rear in my opinion is to tall and will kill your et and trap. 8 sec 2jz use that gearing to trap 160+

Badazzsr20
240sx Wannabe
Posts: 140
Joined: Wed Sep 09, 2009 8:35 pm

Re: Gear ratio question?

Post by Badazzsr20 » Wed Sep 10, 2014 1:54 pm

Ok so I changed my rear to 3.69 from a4.10 and I lost 60/80hp on the dyno. The car made 60hp more on the low end with this diff but dies out on the top end on the dyno. I don't no if it's cause of the diff or if there's something wrong with my car? I'm going to change the diff back and ready dyno it just to see if that's the problem. It's the cheapest fix I can do to check out if this is why I lost so much power....


I'll let u guys know what happens....

Rosado, what diff u used to trap that 145 and what's ur mph at the end of the 1/4?

Also wanted to ask u what car u got and weight does it have?

User avatar
sdaigle240
Belongs To The TOP CONTRIBUTING MEMBERS!
Posts: 4670
Joined: Wed Oct 17, 2007 9:53 am
Location: CONN.

Re: Gear ratio question?

Post by sdaigle240 » Thu Sep 11, 2014 7:54 am

interesting. subscribed.
airman wrote:I'm all about spreadsheets. Bitches love spreadsheets.
schmauster920 wrote:I shall cast my own pistons in the sands of time, then forge them in the depths of hell.. as funds allow
Image
hy35 18psi Build Thread: viewtopic.php?t=38784
RIP MJL best friend of 20 years and the man who showed me 240s

Badazzsr20
240sx Wannabe
Posts: 140
Joined: Wed Sep 09, 2009 8:35 pm

Re: Gear ratio question?

Post by Badazzsr20 » Thu Sep 11, 2014 4:36 pm

Ok so I change it back to the 4.10 and come
To find out that it wasn't the gear at all it was a a ecu problem. But we did see a power and change in the graph that actually helped. I picked up 70 more hp of the couse of a powerband. The other diff "taller" gives me about 60hp.

Your not gaining hp it's just placing the TQ in a better powerband witch in turn give u a better control of the power. I think I'm explaining this right.

So being that u said that your 4.10 gears ran out at the 1000ft did u try a new gear? I'm going to put the 3.69 gears back in cause the 4.10 with 26" talls won't make it to the end without shifting 5th according to you.

Please update us with this info thanks.

BoBaCk1
240sx Wannabe
Posts: 156
Joined: Wed May 27, 2009 7:56 pm
Location: houston tx,guam

Re: Gear ratio question?

Post by BoBaCk1 » Fri Sep 12, 2014 9:14 pm

Hope to see your results. I too am in between keeping my 3.90 j30 diff in or swapping to my 3.69 q45 diff.
Built ka-t
Arias 8:8:1 .20 over
K1 rods
Arp head,main,rod studs
Kelford 272's,dual valve springs
Precision 6262sp .82a/r, peakboost manifold
Cxracing fmic
Fuel injector development 2000cc
Proefi pro128, e85 flex fuel
Rb25 flywheel, dxd 350z clutch

User avatar
s14fiend
Knows Some Stuff About 240's!
Posts: 332
Joined: Wed Feb 09, 2005 7:53 pm
Location: Miami, FL
Contact:

Re: Gear ratio question?

Post by s14fiend » Sat Sep 13, 2014 8:03 pm

Cool thread.... so what about if you launched harder and dumped clutch with some nitrous to spool the turbo with a longer gear (those that you speak of)... you can you can basically make more power and control the tq load better down the track is what your saying?

Sounds like theoretically you would be flying down that track :x lol just gotta let the car cool down good after every pass and not let the clutch burn up.
:x

silvianc
NooB
Posts: 1
Joined: Thu Sep 18, 2014 12:53 am

Re: Gear ratio question?

Post by silvianc » Thu Sep 18, 2014 1:01 am

Im curious about results on 1/4 mile.with q45 3.54 gear. Im using z32 gear box on my rb26 and I just gathered everything needed to do the 6bolt star axles. Ill be running around 600hp. Anybody with this setup? Wonder if i should swap R&P from a j30 or newer q45 3.69. I apreciate your input.
note- Im running t4 twin scroll.manifold woth precision 6262 bb. I shouldnt have any response issue IMO

Badazzsr20
240sx Wannabe
Posts: 140
Joined: Wed Sep 09, 2009 8:35 pm

Re: Gear ratio question?

Post by Badazzsr20 » Sun Sep 21, 2014 9:41 pm

silvianc wrote:Im curious about results on 1/4 mile.with q45 3.54 gear. Im using z32 gear box on my rb26 and I just gathered everything needed to do the 6bolt star axles. Ill be running around 600hp. Anybody with this setup? Wonder if i should swap R&P from a j30 or newer q45 3.69. I apreciate your input.
note- Im running t4 twin scroll.manifold woth precision 6262 bb. I shouldnt have any response issue IMO
from what i noticed from my 4.10 to a 3.69 i didnt see much loss believe it or not. i didnt get to try out the 3.69 much cause i am having a clutch problem and i though it was from changing diffs (long story). i got back to the track but the clutch was slipping so bad i couldnt tell ****. i am trying to fix my clutch and ill head out again with the 4.10 and then with the 3.69 and see what it does.

soon as i get updates i will post!

User avatar
2FAS240
240sx Wannabe
Posts: 176
Joined: Fri Oct 03, 2008 6:21 am
Location: Minneapolis, MN

Re: Gear ratio question?

Post by 2FAS240 » Tue Apr 12, 2016 7:42 am

Is anyone using the 96 Q45 diff with the 3.54 gears?

When I was at the track last summer I couldn't quite make down the 1/4 without having to shift into 4th and losing everything.

At the time I was making 520hp on my KA24DE-T / z32 trans / 96 Q45 diff with 3.54 gr.

Any recommendations on what the best gear set is for the Q45 or just trial and error to find out what works best with my setup??

Sorry to thread jack! This thread just has some good content and just wanted to keep adding to it.

Rb26kouki
Driving Mom's Station Wagon
Posts: 30
Joined: Wed Oct 09, 2013 8:25 am

Re: Gear ratio question?

Post by Rb26kouki » Tue Oct 25, 2016 12:02 am

I'm on the same boat

ICEMAN.KCMO
Knows Some Stuff About 240's!
Posts: 435
Joined: Sun Nov 12, 2006 8:33 am
Location: Kansas City, MO
Contact:

Re: Gear ratio question?

Post by ICEMAN.KCMO » Tue Nov 01, 2016 7:23 pm

subscribed
Steve.

Post Reply