4.5 diff gears in 80 series

[TheBigBoy]

Ive got 2 80 series now. A 4.5 petrol and a factory TD.

The 4.5 petrol has 4.5 diff gears and a rear air locker.
So far the TD (4.1 and 35's) does about (I think) 2200 rpm at 100k's. Is it worth putting them into the TD as it will only increase the rpm at 100 and all its torque and power is down low. So adding to the rpm will just make it worse wont it??

[Auto-Craft]

put em in, it will love it, and get better economy.

Give the TD a tune as well

[TheBigBoy]

I worked it out to about 150rpm difference. Wouldnt it drink more at 100 on a long run though?

[Auto-Craft]

Doesnt sound like much, but as soon as you move them off the sweet spot, they will drink more.

Better off with the diff gears in, we do lots of them, but I wish we could get $4k for em.... LOL

Less RPM doesnt = less fuel, less throttle position to do the same thing = fuel savings though.

THe TD doesnt make all its torque down low though, until you tune it.

[TheBigBoy]

Yep, expensive bloody things. Marks diff gears fitted (drive in out) cost $2700. And $1500 for airlocker

Assassin, so running 35's and the diff gears will use less fuel after tuned and more power in diesel?

I know they make a hell of a difference in petrol. But not sure with diesel still

[Auto-Craft]

Yep,

same difference as you see with a petrol.

With tune, even better.

Normally minimum 10% improvement.