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Limits of strength of factory carriers (and 7.5" IFS fronts)

IowaOffRoad

Practical Engineer
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I've been wondering this for a while, and as I'm repowering my trail rig with a 3.9L this winter, I'm curious as to everybody's experience with factory Toyota 3rds.

What is the biggest deciding factor when deciding between using a 4cyl or V6 3rd member? Power, weight, or tire size?
What weight, power, or tire size should the Toyota stuff be ditched for a heavier duty axle?
What upgrades make sense from a $ standpoint, and what is the $ threshold would be a good time to change to a different axle platform.

I'm currently running 35's, but may swap to 37/38's in the future. Also, looking to build a 4Runner which will probably land about 1000# heavier than my current rig, but will probably not get the extra power, and will probably just have 35's on it. Wanting to possibly run the IFS front for a while.

I'm certain there are 100 different opinions on this, I'd like to hear them all.
 

eat.sleep.wheel

rigless
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Basically ymmv.

And v6 diffs are so plentiful that there is no reason to not use them if you're building up a diff.
 

YotaAtieToo

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Carrier as in the 3rd member assembly or the actual ring gear carrier?

V6 sucks as a welded or lunch box locked diff because the side gears are weak. Once you go to a full carrier locker, a V6 is much better.

As far as the ifs diff. Unless you go to the full rcv set up, (which are not made anymore) the weak link will not likely be the ring gear.

On my 90 4runner, I ran 35s with 5.29s and an open front. Never broke anything doing mild to moderate stuff for 2 or 3 years. The weak link ended up being the spider gear.

On my tracker that I put a 4.56/spartan Toyota ifs center in, the weak link ended up being the intermediate shaft on the driver side. That was kinda a failed experiment, so maybe no apples to apples. But with 1 tire in a bind and a reman cv, that's what broke. This was also with a 4.2:1 tcase and an auto, so quite a bit of tq being applied.

I wouldn't hesitate to run 35s on the stock ifs again for a mild rig. I actually just installed 35x10.50s on my 96 4runner, so we'll see how that goes.
 

TRINDU

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I had a similar thread. The consensus stubs and CVs are the weak point. Followed by the carrier, a $1000 ARB was the solution. Apparently r&p failures are down the list.

I'm still wanting a LC100 diff, but land cruiser guys are cocks
 

IowaOffRoad

Practical Engineer
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Carrier as in the 3rd member assembly or the actual ring gear carrier?…
I guess I’m asking about both. I have piles of stock 4cyl solid axle era stuff, not much v6. I’d like to use what I’ve got as much as possible, but don’t want to waste too much effort on shit that’s guaranteed to fail almost immediately. That’s why I think I’d solicit IBB’s experience here. Hopefully y’all have spent the money twice so I don’t have to:flipoff2:
 
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