Transfer gears versus diff ratios

[duncan]

I have a diesal GQ running 35s and when doing 100ks my tacho reads 2000rpm 400 below my peek torque postion so when towing my camper trailer any small hill kills me and sends me looking for more gears sometimes even down to 3rd also when 4x4ing 1st low range isnt low enough i have to use the brakes going down hill and high range is unusable as the motor dosent develope enough power to push the car

So my question to you is should i fit rock crawler gears to the transfer case for better off roading and just deal with the road manners or should i fit 4.6 diffs so that my towing is better and my low range only down fall to this that i can see is higher fuel consumption for every day driving as the revs are higher any comments would be appreciated also can you fit the diffs from a 2.8 turbo GQ that has 4.6 straight into a 4.2 diesal ie are they the same diff just different ratios

[Area54]

Diesel or petrol? IMO replace the diff gears. Fuel consumption may actually improve (depending on your driving style) as the motor is running closer to peak efficiency. The 2.8 uses the same centre so the R & P will bolt straight on.

[HSV Rangie]

the ultimate answer is to do both.

but first change the diff ratios so that road performence is ok unless you can live with what you have.

Diff ratio change will benifit both road and crawl speeds.
Find the ratio that will bring it back to around stock spec.

Just changing the t/case will not benifit on road at all.

Michael.

[Wendle]

I did the diff gears first (went from 3.9 to 4.88) and fuel economy improved out of sight. This is with the datsun petrol engine, but I can't imagine the diesel using more fuel when it is allowed to spin up a bit more freely, rather than lugging around everywhere.
And the diff gears do improve the offroad side of things quite a lot. You also get more value out of your aftermarket transfer ratios when it is multiplied by a lower diff ratio.