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Diff gears with an Auto XR8 

 

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 Post subject: Diff gears with an Auto XR8
Posted: Sun Jul 23, 2006 2:58 pm 
Getting Side Ways
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Age: 33

Posts: 2058

Joined: 25th May 2006

Ride: ef xr8

Power: 229 rwkw

Location: Perth
WA, Australia

I am considering changing my diff gears in my ef xr8.

After searching through the other diff gear threads i am considering the same.

A few questions i'd like a bit of insight to.

1. Does changing to 3.9 gears change the shift points in D? (ie over revving?)
2. Is there any adjustments needed to be made to the ECU?

3. Is there a replacement speedo gear available for the gear change? (so speedo reads correctly)

4. Fuel usage isnt an issue but would 3.7 be a better alternative all round compared to 3.9 in acceleration vs speed?

The car has only cold air ind and exhaust done and im not looking to warm it up just yet as i've only just clocked up 115k's .

Any help would be much appreciated.

 

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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.

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Posted: Sun Jul 23, 2006 10:04 pm 
Getting Side Ways
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Ride: XR8(EF) & XR8BOSS290 Ute(FG)

Location: Sydney
NSW, Australia

You have two choices with speedo reading & shift points.
You can either have you speed be out, or have your car rev to the s**t house before shifting.
The auto box uses a signal from the speed to shift at certains speeds rather than rpm.

And if you want it to rev you had better do some work to the motor to let it do so freely. :idea:

 

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Posted: Mon Jul 24, 2006 8:56 pm 
Getting Side Ways
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Age: 33

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Joined: 25th May 2006

Ride: ef xr8

Power: 229 rwkw

Location: Perth
WA, Australia

im not after a high reving car just a lil bit more acceleration from it with out compromised top end speed too much and just a bit more response.

I still want it to rev no more than 5 - 5.5k but just so when i put my foot in the sump (occasionally throttle the car) it doesnt rev out to 65-70 kmph
till it changes into 2nd gear. it seems that its out of the cars torque curve at the first 15-20 kmph. i just want to eliminate or shorten this time especially in first gear.

Any more insight would be helpful.

 

_________________

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.

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Posted: Mon Jul 24, 2006 9:17 pm 
Tyre Shredder
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Ride: EB V8

Location: Blue Mountains
NSW, Australia

Said this before but not in here. If you want acceleration (& economy) convert to a manual (you knew someone would say that :roll: ).

1st gear in the auto & second gear in the T5 are almost the same. 1st in the BTR is so rediculously tall that in the EB I could have done more than 100kph before the eeciv cut the fun.

 

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Posted: Tue Jul 25, 2006 12:32 am 
Getting Side Ways
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Ride: 07 BF mk2 E-gas wagon + eb 5.0

Power: 174 rwkw

Location: Adelaide
SA, Australia

although mine's not an ef it is an auto v8 with 3.9 gears. i have the 23 tooth drive gear(black) in the 'box and speedo is still out 15%. it will change into 4th at 70kph on the speedo which is about 60kph in real time. mine is no longer std though so can't say how it will improve your acceleration but for me it launches very hard. i doubt there would be a whole lot of difference between 3.7's and 3.9's either.

as far as manuals go, this is my first auto car and to be quite honest i don't actually mind. it has been shift kitted so changes are pretty good and if you want to go, just stick the boot in. no more getting busy with both legs and arms. nice low loud lazy man's v8.

 

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eb v8: low loud and fast. just how a v8 should be. i guess the big question is, is it fast enough...

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Posted: Tue Jul 25, 2006 12:46 am 
Getting Side Ways
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Age: 33

Posts: 2058

Joined: 25th May 2006

Ride: ef xr8

Power: 229 rwkw

Location: Perth
WA, Australia

Alright thx for ur help guys.

I'll ring around and consider my options.

 

_________________

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.

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