3.08:1 = 1750 @ 100km/h
3.45:1 = 2000 @ 100km/h

3.08:1 = 750kms per tank on highway
3.45:1 = 630kms per tank on highway

3.08:1 = 550-600 per tank in city
3.45:1 = 450-500 per tank in city

All figures recorded in my auto EL Gli I6 with PH4480, high flow cat, 2.5" mandrel bent, 3" intake and K&N panel filter in good cond. with 150,000kms.

An update.
I have now had my diff overhauled, the carrier bearing, and pinion were shot, and it cost me $750.00.
So now I've done the diff, and the wheel bearings.

So now that those noises are gone, I'm left with a couple of remaining ones, and am wondering if anyone can help me out with these?

1.

I get a little hum when cruising 80KMH with cruise control engaged. It's a hum that goes up and down like a sine wave, but goes away when the load comes off and the cars descends down hill a bit, comes back when the load returns. Any thoughts?

2.

When I go to accelerate I get a very small knock in the driveline. If the car is in D and moving at 60 with no foot on pedal, then when I touch the pedal theres a little knock before acceleration. A knock in the driveline somewhere.
When the car is moving, and I put the auto in neutral then back into drive, I get the same knock, but a little louder.
What could that be?

And while I'm asking lots of questions, how much would you recommend I pay the have all the rubber bushes under the car replaced?

Thanks to all.

2 sounds like the uni joints.

I think theres a lot of knocking noise coming from the engine bay.
Almost like theres something unbalanced on the engine, it's transferring a lot of NVH through the rest of the car. Maybe that's my hum at 80kmh?
It says on my receipt, my last check-up found a noisy idler pulley.

Are EL engine mounts worth putting in?

sorry to steal ur thread, but i got a similar problem, so can u just swap centres? or do u have to swap the whole diff?

I've done some very basic research on the drive-line hum phenomenen, and found that many cars around the world, even new ones do it, for various reasons.
Some makers have had to come up with differently designed rubber exhaust hangers and all sorts of things.
This drive-line hum in my car is a vibration around the middle rear of the car at 80kmh. I have a feeling I'd be better off starting with simple things first. Especially now that the car has traveled 166,000 km's.
I should be able to cure this problem by replacing the shockers, suspension and rubber bushes under the car, and maybe look at EL engine mounts?
Does this sound like a good idea guys?

Is the EL engine mounts worth a look at?

How much could I be looking by getting someone to do all the rubber bushes underneath?

Was under the car today, and noticed that one of my front sway bar bushes was split at the bottom. Theres gunk on either side of the bushes on both sides of the car. That would mean a bit of movement.
That would cause a bit of clunking wouldn't it. How hard would that be for me to replace, any ideas gents?

The hum sounds like your tailshaft is unbalanced, or the universals are worn. You could try detaching the tailshaft from the pinion on the diff, rotating the tailshaft by 180 degrees and reattaching it to the pinion. This can sometimes cancel out a slight inbalance in the driveline.
Check for slack in the rear universal joint when you do this.

Thanks. I also just received my Nola-thane bushes to do the swaybar. I am surprised to see that the big ones come the factory with a split in them anyway so what the difference?
Now after all that I have a blown bearing in the idler pulley. Looks too hard to do myself..

The split is how you get them on!
When you do them, use lithium grease on the inside of the rubber.
Also, do up your swaybar links when the car is on the ground, and don't do them up so tight that the polyurethane distorts.
Should help minimise/eradicate any 'knocking' over bumps from the bar.
I'm assuming you got nolathane swaybar link bushes as well?

Yeah I decided to do all the swaybar bushes. Thanks for the info.

BTW all I have is Silicon spray, will this be enough?

I read somwhere that with the Nolathanes, I have to have the car level, with wheels unladen, before I torque up the swaybar bolts. What a pain in the a** for home users..
Is it really all that important that it has to be done this way?