Optimal diff ratio and wheel size for 4 speed auto ecotec? (VYII Acclaim)

[BenMitchell]

Also, is the SS 3.46 diff a lsd?

 

[james1988]

You can have whichever diff ratio you like on whichever gearbox you like.
So yes it is compatible.
And the vy ss has LSD. But whether or not it's still working is another story.
The lsd's in commodores aren't renowned for durability at all.

 

[Surfwagon]

I did a search and it looks like the auto option for the VY SS uses the same transmission and 3.08 diff as the auto V6. From which model would I be using a 3.46 diff to suit the 4L60E transmission? Assuming I've read correctly the SS manual has a 3.46 diff. Is this compatible with the 4L60E transmission? Thanks

My Senator is a 4spd auto simialar to yours and comes std with 3.46 LS diff so it does not matter what diff ratio you use behind any transmission, you just need to get the speedo corrected by some one with "tech2" once you have changed the ratio.

 

[BenMitchell]

Good to know. So it's just a straight swap of the diffs? Bolt on the 3.46 lsd and get the speedo recalibrated? I've read this only costs about $50 to get done but i'm not sure where i would go to find someone with a "tech 2".

 

[Kernal]

My personal experience.

Ive got a VT V6 Auto. Engine is completely standard. VE SS 18" wheels and 4.11 diff gears, limo.

Taking into account the speedo and odo readings are out by 25% (yes I am that accurate lol) I still manage to get about 530-550km per tank. whereas with the 3.08 ratio i was only getting about 30kms more. So fcuk all difference.

I wouldn't worry about top speed. how often do you plan on clocking your car lol.

 

[BenMitchell]

My personal experience.

Ive got a VT V6 Auto. Engine is completely standard. VE SS 18" wheels and 4.11 diff gears, limo.

Taking into account the speedo and odo readings are out by 25% (yes I am that accurate lol) I still manage to get about 530-550km per tank. whereas with the 3.08 ratio i was only getting about 30kms more. So fcuk all difference.

I wouldn't worry about top speed. how often do you plan on clocking your car lol.

Just for an idea (if you know).. how fast was your VT capable of going with the 3.08 diff compared to now with the 4.11? I imagine it accelerates like a rocket but is the top speed reduced by a significant enough amount to inhibit overtaking on the highway or something?

When you change the diff do the shift points for the gears need to be modified?

 

[Kernal]

Just for an idea (if you know).. how fast was your VT capable of going with the 3.08 diff compared to now with the 4.11? I imagine it accelerates like a rocket but is the top speed reduced by a significant enough amount to inhibit overtaking on the highway or something?

When you change the diff do the shift points for the gears need to be modified?

You'll have no issues with overtaking man. With the 3.08 I clocked it. Speedo goes to 220. And with 4.11 about 170 but i wasn't trying to see what my top speed was so there was a bit more in it (that was with a mate along side, his speedo was correct, obviously mine was out cos of the gears). And no i dont have a 'private road' as so many people on here do lol. It was a track day.

Shift points did change a bit but theres no need to modify them.

 

[james1988]

3.08 to 4.11 is 33% difference.
So with absolutely ever speed and every gear and everything. There will be 33% difference.
If the cars theoretical top speed is 240 with 3.08 then it will now be 160.

At any speed your revs will increase by 33% also.
So you can work out maximum speeds in certain gears and whatnot

 

[james1988]

25% sorry. Not 33

 

[showbags]

I've got 3.45's and mine uses less fuel now than what it did with 3.08.

Mine uses nearly 10% more

I've got a 2500 hi stall as well, but I drive like a grandpa most of the time.