Diff Gears - Advice Please

[Bigrig]

G'day all

I have read things on the net, I have had people tell me, and I have read some of the other posts, but can someone PLEASE tell me the absolute reasons for getting the diff gears replaced with lower reduction cogs. I have 33" tyres which I wouldn't have thought made that much of a difference, but apparently they do??

Specifically, do diff reduction gears really allow you:

1. to sit in taller gears when towing/going up hill etc hence using less fuel (that is one I have heard);
2. to bring your vehicle back into the manufacturer specified "power band" (post the fitting of taller tyres) and hence you should see an improved power performance, again potentially with improved fuel consumption figures as a result
3. to change the way lower gears (1st and 2nd primarily) behave so you have more 'pulling power' off the mark; and,
4. other benefits I haven't mentioned??

And finally, IS IT REALLY WORTH IT FINANCIALLY??

Thanks a million in advance people - appreciate any and all feedback ... and yes, thinking of getting them, but obviously I don't know why as yet!! LOL

[Maxhead]

From my limited knowledge higher diff gear ratios will allow you to achieve the above.
I don't know the cost aspect of it though

Don't confuse with reduction gears in the transfer which are for better crawling speeds in low range

[YNOT]

These are not exact figures but, a standard GQ diesel with 31 inch tyres and 4.1:1 diff gears might get roughly 12 l/100km and sit on 2200rpm at 100km/h. If you fit 33 inch tyres you could expect to get around 13 to 14 l/100km and 2000rpm at 100km/h. Not a big difference.
If you were to switch 4.3:1 diff gears you would be very close to the same economy and cruise revs as standard. Likewise using 4.6:1 diff gears to run 35 inch tyres. Is it worth $1000 per diff supplied and fitted for different ratio's to run 33 inch tyres, most people myself included would say no. I've fitted 33 inch tyres to all 4 of my Patrols without changing diff ratio's, and had no problems towing or 4WDing. I would consider changing diff gears if I was changing to 35 inch tyres.

Tony

[Bigrig]

Nisspat/Tony - thanks for the information guys - Tony, I sort of shared your view but didn't have enough information to argue the point recently when someone told me that I could essentially get better performance from my rig by changing the diff gears. Been looking at different things to get a bit more out of it and the whole tyre conversation came up and I just couldn't see that fitting 33"s would make that much of a difference ...

Anyways - appreciate the comments as always!!!