This actually makes a hell of a lot of sense. The 'deal' with diff gears, in practically any production diff, is that the pinion isn't in the centre axis of the crownwheel, it's down below it. That means the gears don't mesh like a gearbox gearset does, they actually slide across one another. This generates big loads, and potentially, lots of heat (and it's also why you need to run hypoid spec oil - hypoid being the eng term for the offset pinion/crownwheel gear arrangement - and it's also incidentally why you _don't_ want to use hypoid oil in a conventional gearbox, as some of the stuff required to make hypoid gears survive isn't as ideal for conventional gears). If you are curious about the heat aspect (and the heat the gear surfaces run compared to the oil can be a lot hotter) - remember more than a few race cars run pumps to route fluid to and from the diff to a cooler. Another interesting tid bit, diff oil viscosity is rated on a different scale/system than engine oil, and when it's up at operating temps, 'thick' diff oil pours/flows similar to something like castrol gtx2 engine oil!

On the 'straight cut' option - believe it or not helical gears in a gearbox (if they are made of the same stuff and are the same basic dimensions, and similarly finished/treated) are actually stronger than straight cuts, they just 'lose' a little bit of power as some of it is wasted due to the helix angle trying to force the gear forward or backward in the gearbox casing, ght cuts transmit it all to the next gear (or as much as is practical). On a limited (relatively) power NA racer, you need every % you can find, hence their use. they are also frequently made to a much higher standard than mass production stock engined cars gearsets would be!

In terms of percentage benefit of polished gears, I doubt you could find a massive difference in power output (you might if you kept it on the dyno long enough to really start cooking the diff oil, which would be 'great' for the rest of the engine/driveline!!) but it'd certainly be (at least potentially, and of course it's down to how bad they were to start with, how well it was done, how close to failure the std sets were etc) possible to extend longevity as much as 2-3 times on a circuit racer differential's life. Mostly because it'd be preventing the oil overheating toward the end of a race, and once that happens, even small amount of use, like 1 lap, causes massively accelerated wear.

These comments are general from stuff I've had any exposure to, not necessarily datto specific, and I'll happily stand corrected if there was other stuff going on, I don't mean to speak for the original poster in any way!

Quote:

The season kicks off shortly for the GT3 lads and we will not know for about 6 months or more when we get the box back. It will work, as it has been proven in the past with regular ol straight cut gears. GRM has been doing it for years and with our SG gearbox's that were dropping a tooth off, after polishing they have not needed to replace gears yet. They are homoligated in the Focus rally car somewhere in europe and they can only buy our gears so it does work. We have just never tried it with diff gears. When you buy a C/P from Astin Martin for racing purposes they come polished. It must do something.

not sure who your asking but i geuinely want to know what percentage benefit this would give?

Are you guys taking the piss or what?
I Suppose a smooth surface would reduce wear a fair bit.

i have one of those polishers at work, might invest in some different grade stones and give something like this a shot

DID IT WORK? any decent result from doing it?

i wonder were i could get them done around mandurah

Firstly the gears get soaked in acid for about 8 to 10 hours and then they get placed into a container filled with ceramic stones shaped like triangles. The container is also filled with a solution that has a chemical reaction th the acid causing the gears to vibrate. After about another 10 hours you pull the gears out looking like chrome plated gears. At about $2K for a crownwheel / pinion you would see the point in making it last as long as you can.

Yeah good tip, I might polish my roll cage to make it stronger! :) just kidding, really!

what would u recomend polishing the diff gears with? wire wheel? or is their some speical tool to polish the gears with?