Diff gears....

[torana355]

Correct, no tangible benefit until you reach 200km/h+ acceleration as per the above.

Yep and when you have a 6L V8 that makes mountains of torque all you are going to do is wheelspin in first gear making the car even harder to launch and making your 0-100 time even slower. The one benefit for a street car will be in gear acceleration for overtaking but worse fuel economy and slower 0-100kph negates that imo.

 

[PIR4TE]

Yep and when you have a 6L V8 that makes mountains of torque all you are going to do is wheelspin in first gear making the car even harder to launch and making your 0-100 time even slower. The one benefit for a street car will be in gear acceleration for overtaking but worse fuel economy and slower 0-100kph negates that imo.

Exactly! Lower gearing in a stock Zeta V8 will not put you in front at traffic lights or over the 1/4 mile. Tune your car to a totally different operating range (specialised camshaft, headwork, race intake and exhaust mods) and it starts to pay off. However the trade off is a narrower powerband skewed to high RPM, and it takes proportionally higher RPM (HP) to compensate.
Then again there's an argument that similar mods for torque and stock diff would be smoother, more economical and last longer, particularly with your AFM auto.
3.27 is obviously midway between stock and 3.45.

 

[christov]

Exactly! Lower gearing in a stock Zeta V8 will not put you in front at traffic lights or over the 1/4 mile. Tune your car to a totally different operating range (specialised camshaft, headwork, race intake and exhaust mods) and it starts to pay off. However the trade off is a narrower powerband skewed to high RPM, and it takes proportionally higher RPM (HP) to compensate.
Then again there's an argument that similar mods for torque and stock diff would be smoother, more economical and last longer, particularly with your AFM auto.
3.27 is obviously midway between stock and 3.45.

I agree to a degree with regards to 3.27s, however from the comparison that I ran for my vehicle their was still no benefit in 0-100 and over the 1/4 mile mainly due to the relatively slow shift speed.

In gear acceleration however is a different story. I can appreciate that a different operating RPM will make it start to pay off in some areas, however as you mentioned it will actually negate some if not most of these benefits on a street car that is driven legally 95% of the time.

That being said though, it's horses for courses. I ultimately left my ratio stock after doing the analysis and reviewing my driving pattern, others have changed and been very happy with it which is great for them.

I hope OP has received some good insights from this thread, and gets the best result for him!

 

[arronm]

That may be true. But go drive 2 cars with similar mods and 2.92 and 3.45 diff ratios and the. Tell me which one feels better for a street car

I do agree though once you go over 300 rwkw or fit a blower 2.92 would be best to control wheel spin

 

[PIR4TE]

I may need to increase tyre width too, 245/45 R18 are on there at the moment.would 265 or 255 fit in there?....

Yes both will fit no probs, I have 255 Sumitomos all around.

Also regarding the TruTrac mechanism, depending on how and where you drive but for me it is the most significant improvement to dynamic cornering and handling you can buy. You won't believe what a difference it makes out of corners. So stock gears for straight line and economy, TruTrac for twisties, and lower gearing for in-gear and twisties.

This is why it works
[video=youtube_share;JEiSTzK-A2A]http://youtu.be/JEiSTzK-A2A[/video]

Cue to 11:00 to see how it works on Z28 and why it beats exotica AWD around a circuit, basically it doesn't hook up on deceleration which makes it easier to point into corners:
[video=youtube_share;PqkyWhVBSKU]http://youtu.be/PqkyWhVBSKU[/video]

 

[torana355]

That may be true. But go drive 2 cars with similar mods and 2.92 and 3.45 diff ratios and the. Tell me which one feels better for a street car

I do agree though once you go over 300 rwkw or fit a blower 2.92 would be best to control wheel spin

Yes the in gear acceleration will make the car with the 3.45 gears feel quicker, but in reality the 0-150kph is going to be very similar. The time you make up with in gear acceleration is lost with the time it takes to make extra gear changes to reach the same speed. A DSG gearbox would change things!

 

[christov]

That may be true. But go drive 2 cars with similar mods and 2.92 and 3.45 diff ratios and the. Tell me which one feels better for a street car

I do agree though once you go over 300 rwkw or fit a blower 2.92 would be best to control wheel spin

I have done so, and in my opinion I prefer the 2.92 over the 3.46 that auto I drove. In manual mode in gear it does feel quicker but as Torana355 stated, we don't have a DSG gearbox that has lightning fast shift speeds. As such the higher ratio creates a slower 0-100 and 1/4 mile.

The fact is, if you take a VF SS with the standard bolt ons and tuning you will be faster in acceleration everywhere sub ~240kp/h and for most practical street use.

Also for OPs purpose, changing to 3.46s with a non-LSD is likely to create even more traction problems. However if he gets the TruTrac setup it will help negate that.

You're definitely correct on 300+rwkw, the 2.92s would be beneficial for traction.

 

[Foggsy]

There's a lot of respect out there now for the Wavetrac diff centre. I've driven 2 of them and was super impressed. What do you think Pirate?

 

[calvv8]

Imo changing diff gears in a car that already has a short first gear is counter productive on a street driven car. Your 0-100 time will be slower due to three gear changes to reach 100kph, you wont see the benefit till you are well over the speed limit. You really need gearbox ratios that complement the diff gears.

Well now that has just thrown a spanner in the works.....:-/

Maybe i need to wait a bit and gather every single bit of info on this...0 to 100 would surely be quicker with 3:45 LSD set up than standard 2:92....Surely.....

In regards to the shift times ive had all the gear changes sharpened up big time from standard...

 

[christov]

Well now that has just thrown a spanner in the works.....:-/

Maybe i need to wait a bit and gather every single bit of info on this...0 to 100 would surely be quicker with 3:45 LSD set up than standard 2:92....Surely.....

In regards to the shift times ive had all the gear changes sharpened up big time from standard...

Simple maths mate. It won't be faster. In gear acceleration will improve as mentioned throughout this thread numerous times. Due to the comparatively slow changes from our gearboxes you will not be faster in a straight dash to 100 or the 1/4 mile.