Fordmods Logo

diff gears? quicker quarter mile or not? 

 

Page 1 of 1 [ 12 posts ] 

 
 Post subject: diff gears? quicker quarter mile or not?
Posted: Fri Dec 07, 2007 11:29 pm 
Stock as a Rock
Offline

Posts: 181

Joined: 7th Dec 2007

Location: sydney
NSW, Australia

Hi,

I have a blood orange XR6 turbo with 295rwkw, 4 speed auto with 2800rpm stall converter. Im thinking about diff gears?

Im thinking about a 3.73 or 4.11 ratio from my standard 3.45 ratio. My concern is that the car might actually be slower over the quarter mile with the gears?

My concern is that with shorter ratios, the car may change into fourth down the quarter mile which will result in poor acceleration? the standard gears may stretch out 3rd gear but wouldnt that result in better acceleration than being in 4th gear? Someone also said the XR6 turbo likes to be loaded up not have short gears?

Down low it should be quicker? what are the thoughts of the members?

 

_________________

Gone to a better place

Top
 Profile  
 
 
Posted: Fri Dec 07, 2007 11:55 pm 
Getting Side Ways
Offline
User avatar

Age: 29

Posts: 975

Joined: 26th Nov 2004

Ride: el falcon

Power: 608 rwkw

Location: Waroona
WA, Australia

1/4 mile will be slower if it changes into 4th.

i would just stick with 3.45's but if your keen for a change then go the 3.73. i dont think u will go into 4th with the 3.73 but it will be close.

 

_________________

# 1997 EL Falcon GLI - 600+rwkw

# 2008 FPV FG GTE - Xa Coilovers, 20x8/ 20x10 Fairladys

Top
 Profile  
 
 
Posted: Sat Dec 08, 2007 12:18 am 
Getting Side Ways
Offline
User avatar

Age: 33

Posts: 2058

Joined: 25th May 2006

Ride: ef xr8

Power: 229 rwkw

Location: Perth
WA, Australia

It would result in a quicker quarter mile time for sure.

Having the shorter gears means getting the car in the torque range earlier and with that slight reduction in gearing, accelerating alot better too.

I just wouldn't go too tall though, 4.11's is a bit much. 3.7's would be a great trade off, though I was under the impression that turbo likes tall gears, as when they hit boost they can get a big surge with all that extra torque with the gearing?

Also depends on what sort of rev range, boost you are leaving the line with too.

 

_________________

Because of Beer, Thirst is a Beautiful Thing!

'95 EF XR8 auto, Advance headers, 3" exhaust, Cobra manifold, BBK 75mm throttle body , 80MM Marauder MAF, Vortech V2 T Trim , 307 rwhp, 405 ft/lb 13.2 @ 105 MPH

Now N/A (permanent Lag) - AFR 165's, Comp XE270 cam, 1.6 RR - 269 rwhp 14.1 @ 102mph.

Top
 Profile  
 
 
Posted: Sat Dec 08, 2007 12:20 am 
Getting Side Ways
Offline
User avatar

Age: 32

Posts: 4401

Joined: 25th Mar 2005

Ride: BA XT, BA XR6T, ED Ghia 5.0

Location: Perth
WA, Australia

What sort of mph are you doing across the line.. also if you don't have slicks yet there's no question what your next mod should be.

 

_________________

What's the difference between a Holden and a sheep? It's less embarrasing getting out of the back of a sheep..

Top
 Profile  
 
 
Posted: Sat Dec 08, 2007 12:30 am 
Stock as a Rock
Offline

Posts: 181

Joined: 7th Dec 2007

Location: sydney
NSW, Australia

So do turbos like to be loaded up with long gears to take advantage of the surge or is it better they quickly wind out and pump through the gears.

Someone told me with 4.11's all i will get is wheelspin and it will hit into 4th gear down the quarter which will be crap. Apparently all the guys doing the quick times in XR6T's have stock diff gears? They pretty much ignore them.

I used to have a LS1 and diff gears made a huge difference in that car.

People are warning me not to do it to the T?? what do you think?

 

_________________

Gone to a better place

Top
 Profile  
 
 
Posted: Sat Dec 08, 2007 9:12 am 
Getting Side Ways
Offline
User avatar

Age: 33

Posts: 1239

Joined: 1st Jul 2005

Gallery: 9 images

Ride: EF XR8 & 2002 GSXR-1000

Location: Perth
WA, Australia

What is your current 60', ET & trap speed?

Being an auto, I wouldn't have thought the gear change would hurt it much (far less than if it was manual anyway).

 

_________________

The fast fun: Suzuki GSXR1000
The one I use when I can't use the fast fun: Blown EF XR8

Top
 Profile  
 
 
Posted: Sat Dec 08, 2007 9:19 am 
Getting Side Ways
Offline

Posts: 6166

Joined: 8th May 2007

i would assume 3.7 lsd would be good for accelration and is still a fairly tame ratio behind the auto.
Top
 Profile  
 
 
Posted: Sat Dec 08, 2007 9:52 am 
Getting Side Ways
Offline

Age: 34

Posts: 3406

Joined: 7th Feb 2005

Ride: AU2 Ute

Location: melbourne
VIC, Australia

Figure out what rpm you are crossing the line at first then decide.

Personally i wouldnt bother. My AU was running 11.8's with the stock 3.45's crossing the line at 120mph. I cant remember if it was changing into 4th or not though.
Top
 Profile  
 
 
Posted: Sat Dec 08, 2007 11:18 am 
Getting Side Ways
Offline
User avatar

Age: 33

Posts: 1442

Joined: 26th Apr 2006

Gallery: 6 images

Ride: 97 EL XR6

Power: 162 rwkw

Location: liverpool
NSW, Australia

im running stock 3.45s with a 5 speed, i JUST need to pick up fourth gear as i cross the line.

from what ive heard, if you do need to pick up fourth gear earlier because of diff gears, then your better off hitting it as early as you can so you can cross the line high up in the rev range maximising that gear... so you would have to work out what ratios would be close to redlining 4th at the 400m mark. 4th is a long gear and at that spead with tall gears the turbo should love it...

but with such gearing, and 300rwkw, youll have a hard time getting off the line!

also i dont see the point of getting 3.7 gears and crossing the line at 4,000 rpm in fourth gear...

if you cant get the info in here id look into the xr6T clubs, cos im sure someone has done this...

 

_________________

07 BF MKII XR6T
310rwkw @ 13psi - Tuned By CMS

Top
 Profile  
 
 
Posted: Sun Dec 09, 2007 11:53 am 
Stock as a Rock
Offline

Posts: 181

Joined: 7th Dec 2007

Location: sydney
NSW, Australia

i have not run the car yet. From the mods, the tuner says pretty flat 12 is achievable. The tuner also says chuck in the 4.11s so i dont know what to beleive.

I would have though in a 4 speed auto, the best quarter mile would result from crossing the line at about redline in third gear, up around the 120mph mark? thats probably what the stardard gears would achieve but 4.11's would certainly force a change into 4th and kill off the surge up top.

 

_________________

Gone to a better place

Top
 Profile  
 
 
Posted: Tue Dec 18, 2007 5:13 pm 
Getting Side Ways
Offline
User avatar

Age: 39

Posts: 1886

Joined: 26th Nov 2006

Gallery: 7 images

Ride: EL XR8, '08 Mondeo XR5t

Power: 205 rwkw

Location: Perth
WA, Australia

Take it for a run if you haven't done so already before touching the diff. That way you'll know if you need to change or not. It'll hurt less than making the change and discovering you've made the wrong decision cos you can't get the wheels to stick to the track!

 

_________________

Trickflow Street Heat top end kit, 70mm BBK TB & EGR, 24lb injectors, Underdrives & 3.73s: 275rwhp - 13.15@105mph NA / 12.37@116mph N20

When injustice becomes law, resistance becomes duty

Top
 Profile  
 
 
Posted: Sun Dec 23, 2007 3:55 pm 
Getting Side Ways
Offline

Age: 27

Posts: 1323

Joined: 12th Nov 2006

Gallery: 9 images

Ride: 02 xls ute 347

Location: adelaide
SA, Australia

2 sp powerglider with 5000 stalely and 411s will be perfect for your car it will hit full boost threw both gears and wheel spin wont be as much of a factor

 

_________________

02 series 3 AU marline ute 5speed 347 stroker

Top
 Profile  
 
Display posts from previous:
Sort by  
 Page 1 of 1  [ 12 posts ] 

Who is online

Users browsing this forum: No registered users and 12 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

 

 

It is currently Sun Dec 17, 2017 9:32 pm All times are UTC + 11 hours

 

 

(c)2014 Total Web Solutions Australia - Australian Web Hosting and Domain Names