The gx has a center locking diff and the four runner a rear locking diff. Which would be better and why

Depends on how you're going to use it. You need to read up on the differences between full time 4WD, part time 4WD, AWD, and Toyota's Multimode center diff, and you need to read up on how a differential works and what locking it means.

In short, an open center diff lets you use 4wd on the pavement similiar to AWD cars, or you can lock it and it acts just like a tradition part-time 4WD. The locking rear diff is an entirely different animal - it locks the two rear wheels together at the differential, which adds traction off road.

The gx has a locking center diff. I thought that was different than an open centre diff.

I will be using mostly on pavement but we have heavy snow cover for five months a year. When I go off road it won't be moguls or ruts but heavy snow over graded dirt road.

I also have to tow a 4000lb boat

I currently have an 02 tundra 4 x 4 hi lo range and limited slip. The traction is not sufficient on the snow covered dirt roads

Which has nothing to do with your 4wd system and everything to do with the tires on the car. Your tires make up at least 80% of your car's snow performance. A FWD Camry with snow tires would destroy any 4runner on the stock tires in the snow.

Which is why you need to understand the difference between part time 4WD with no center diff, full time 4WD with an open center diff, and Toyota's multimode with a lockable center diff. I've summarized the differences above, which should be enough to get you pointed in the right direction.

Better tires are what you need then, because your Tundra with limited slip is exactly the sort of truck I'd want in those conditions - an open center diff will lose traction immediately, and a locked rear will break free and spin out too easily.

Just a note, the GX460 has a lockable torsen center diff and will actually do better than a locked center in the snow during turns by not binding and causing the tires to start slipping causing an even bigger slide. The only time you're better off locking it is when rock crawling.

Still, either a new Trail Edition or GX460 will need completely different tires to perform in the snow. The stock tires will not cut it at all.

Got decent winters lots of tread left. Perhaps I should upgrade though. New tires would be a lot cheaper than a new truck. Not as much fun though.

Would the gx center lock system perform similar to my tundras 4x4

I have read up on the Toyota four wheel drive systems but is confusing as all heck

Loss of traction I am having happens on significant twisty uphill grade. Don't know if that changes anything.

I' m thinking atrac with 4x4 kdss would be an upgrade over my current setup?

atrac only helps if you're spinning one tire. Kdss won't make any difference.

Which tire brand and model is this?

Firestone winterforce. They probably have about 60% tread left. Well above wear bars

When I'm going up the bigger hills everything is spinning and sliding. Thought atrac might kick in and help at that point. I am probably losing some contact with the ground on a tire or two when i get speed up going up hill around a corner. That's where I thought the kdss may help.

So the 4x4 systems on the gx and trail edition aren't a substantial improvement over my tundra for what I do?

That's a pretty good tire. Anyone else have an easier time getting up the hill? It may just be too difficult for any car to do in the snow.

If anything the limited slip in your tundra rear is actually better. Open diffs and atrac would be a downgrade.

Another idea, in deep snow, mud or aggressive all terrain tires actually have an advantage over winter tires due to their ability to churn snow, you may want to give that a try. But on ice, snow tires always win. You may want to give something like a Duratrac a try.

A new ram 1500 had an easier time but he had new blizzaks. I'm going to try new tires. We have lots of ice here too so I don't want to give up on my winter tires unless I'm confident the mt's will be good with ice. Maybe mt's with studs. I'll have to do some research. Thanks for your posts they have been really helpful

I don't think you have explained the GX 460 features. The top line GX has a torsen high technology limited slip differential, various traction control settings that prevent individual wheel slippage, and a rear differential that can be locked. The KDSS suspension system can provide much greater wheel contact, but only in very steep terrain.

If a front wheel spins going up the steep incline, the torsen limited slip diff will apply more power to the rear wheels. However the traction control system should also apply some brakes to the spinning rear wheel.

But this is irrelevent - because the GX 460's top model has an off road mode, that normally only operates in low range (hence the vehicle goes much more slowly). But there is also a high slip condition mode, that operates in normal gearing mode ie muddy, sandy, dirt, slippery or in snow. This mode is the first on the menu, Mud and Sand mode. This modes can be selected by selecting Multi-Terrain, and then selecting that first menu, mud and sand, and then all the vehicles senses change. Even the ABS braking changes its operational behaviour. IF there is a bad hill or tricky part in the snow drive, the Gx 460's multi terrain will use all its sensors to get you through.

As others have said though - tyres are much more important but with the right tyres a GX 460 would go around that hill I suspect terribly easily. You need a test vehicle from Lexus for a winter weekend. They'd lend you one in australia for such a test - successful tests like that sell vehicles. Ask your dealer about a test vehicle for a snowy weekend, and get them to explain to you about how you should engage mud sand (and snow) multi-terrain mode before you leave the dealership.

The GX has the same lockable, limited slip Torsen center diff as the 4th Gen (all trims) and 5th Gen (Limited trim only). When locked, it behaves just like a part-time system -- the front and rear driveshafts turn at the same speed. When unlocked it is not an "open" diff -- it is still limited slip.

As for which is "better", for onroad use in snow, I prefer fulltime 4WD over the 4Runner Trail Edition's part-time 4WD system. For offroad use, the Trail Edition's ability to lock the rear diff gives it the edge.