ref:...........my 4runner 2008 V8
Local guy has 265/75/17 tires on 7.5W wheels. 2 tires look pretty OK, other 2 are worn down. probs ? need 2 new tires? what happens if I mount these. different rolling Rad an issue?

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The AWD system on the V8 likes/needs tires that are within 4mm size of each other (iirc)

That said, those two worn ones would definitely need to be replaced imo. Looks like on any wet pavement you'd be sliding around with how worn those treads are

If you have AWD you want to match your tire diameter if at all possible. That being said a small amount of tire diameter difference won't hurt but a large amount will. Measure the two tires and compare to new (new info is on line) so you know how much is worn. As you said 2 of those are total junk and you should get a discount because you will pay the disposal fee...lol.

The Torsen T3 likes similarly sized tires (an unofficial number I have heard repeated over the years has been 3~4/32") on both axles. The All-Time 4WD system the V8 4Runners use is slightly sensitive to it, it may not blow up the transfer case. But the difference in speed of the two axles when the tires are significantly different in size between front and rear axle will cause the Torsen T3 center differential to overwork itself.

If you had 2 big back tires and two smaller front tires, your transfer case would be overworking itself. But if you had a large tire and a small tire on the same axle, that differential could overwork itself because it would think you are constantly turning (not very sharply) because the CV shafts on each side would be spinning at different speeds. The diff might experience more wear but your transfer case couldn't tell a difference. Therefore it could be better to have the taller tires at the FR and BL positions. Would this be correct?

Don't want to hijack this thread but I hope it's not too far off topic to ask if one under inflated tire. (bad me, but Ive been dealing with a flare up of a thyroid condition that throws off ones sense of awareness reason). And I mean really under inflated tire like 15 psi under, could cause the transfer case to overheat too the point of expanding out the vent? Again I apologize to the sewgan if this doesn't belong here but don't know how to move a quote to another thread and BlakWorksLnc post states one concept I was considering but discounted because I figured only one tire per axle would likely take a told on that axles diff before the center diff. And this is about the issue of ill effects of mismatch tire diameters.

This thread tries to describes the issue I'm dealing with: http://www.toyota-(4runner.org/4th-g...e-related.html

And by the way don't let that thread title throw you, at the time I mean temperature as in climate not as in equipment temperature.)
ps: the fluid is not burnt by any means.

Even if you could run all 4 of those tires, doesn't mean you should...

Two of those things are just too far gone.

Your link isn't working, so I can't say for sure, but here's a rough guess based off your post:

I don't think it'd get that overheated that it'd start boiling fluid out of the vent (especially if it's not burnt looking.) My first guess would be that the transfer case was over filled, which is something I do see often from other quick lube places. Another guess would be that the fluid is not the correct fluid for the vehicle and it's foaming or something.

I think I fixed the link for him... the URL probably got messed up from a copy/paste Actuator leak temperature related?

Oh the actuator seal leaking due to colder weather might be indicative of the seal starting to fail. Seals become hard/stiff over time and don't rebound as properly as they should. My best theory on that is when they are starting to be come that hard/stiff they'll shrink a bit in colder weathers and not rebound as well as they should until they warm up causing a seep. At least that's the only thing I can come up with it being that temperature sensitive.

Thanks

Good point. I lived on the west coast for nearly half my life so I can fully understand how a west coast guy may not have get a true appreciation for what fluids are like at sub-zero temps. Once, back in 94, I started a nearly new manual trans Accura which sat outside overnight at -34f. It turned over sluggish but started well enough. However, due to the thickening of the gear lube I had to hold the clutch in for about 20 minutes before the fluid thinned enough to let the poor thing idle in neutral.
I use the above example to back a possible theory for the self-healing actuator leak. Thinking: the cold stiff rubber together with the cold stiff lube wrapped in the cavity around the spring caused fluid to leak past the seal or that extreme cold may have finally compromised the o-ring to the point to shrink enough to release some lube. But, what baffles me here, why cleaning it up stopped the leak but really I've never been inside an actuator case and thus ponder this question: could conditions causing a seal leak leading from the torque converter to the actuator case result in the case partially filling with fluid which would then slowly drip out over the next few weeks? I'd like to figure this out but I guess if the leak returns intermittent or not I'll figure "it ain't gonna get no better by itself" and bite the bullet and drop the thing and replace the seals and likely the input and out put seals as well while I'm that close. That is unless common experience suggest leave these alone if not leaking. But I know they have 17 years (yikes hadn't thought about that for awhile) on them. In an extreme climate no less.