Can someone explain this to me about diff/axle strength...

[realm]

So I've read 50 million threads on here about recommended tire sizes and the axle strength, etc.

General concensus seems to be 33x12.50 is max recommended for M1009.

However, what is the weak point of a diff when they talk about this? Is it actually going to snap and break, or is it the inside gears that fail or what? If inside then couldn't you just replace it with a stronger ring and pinion gear?

Where I'm confused, is how do I see little Toyota's running around with these puny looking axles and yet running 36" tires all day long? Some of them I know are stock axles.

Are the Blazer 10-bolt's really that weak even compared to a little Toyota?
With that said, I love Toyotas... had a Tacoma with 33's I beat the crud out of and it never quit.

I'm just confused because for my use around the farm and city the Tacoma with 33's never failed me, so I'm wondering if I can do the same with cucv and 35's, or if the axles are really that much weaker.

Thank you.

 

[tsmall07]

It all has to do with the weight of the truck, the design of the axle shafts, and how heavy your right foot is. The first thing to go in a 10 bolt is the axle shafts, primarily at the ujoint. Toyotas can run larger tires because they weigh a lot less, so there is a lot less torque on the shafts to get the truck moving. Secondly, the birfield joint that a yota has is a stronger design than the ujoint that a 10 bolt has. Thirdly, you can run 36s all day if you don't push the loud pedal as hard.

You can get chrom-moly shafts for your 10 bolt and be able to run big tires, but it would be easier and cheaper to just get a 60.

Oh yeah and another reason 33s are the largest suggested is because of how tall the gearing is in a stock 1009. It's hard to turn big tires with tall gears.

the r&p is the weak point of some axle (ford 9") but you can't really replace with a stronger piece without getting a bigger r&p set, which requires a bigger housing... meaning you have to replace the whole axle.

If you want big tahrs then switch to some axles from a 1008

 

[11Echo]

I've run 33/12.50-15's on 8" wheels for over 30 years on several GM half tons and never busted anything axle related. My one 1/2 has carried an 8.5' Western Pro plow since 1984 and it is a heavy sucker. All these have had 3.73 gears in them unlike the 1009 and it's 3.08.

 

[AJMBLAZER]

It all has to do with the weight of the truck, the design of the axle shafts, and how heavy your right foot is. The first thing to go in a 10 bolt is the axle shafts, primarily at the ujoint. Toyotas can run larger tires because they weigh a lot less, so there is a lot less torque on the shafts to get the truck moving. Secondly, the birfield joint that a yota has is a stronger design than the ujoint that a 10 bolt has. Thirdly, you can run 36s all day if you don't push the loud pedal as hard.

You can get chrom-moly shafts for your 10 bolt and be able to run big tires, but it would be easier and cheaper to just get a 60.

Oh yeah and another reason 33s are the largest suggested is because of how tall the gearing is in a stock 1009. It's hard to turn big tires with tall gears.

the r&p is the weak point of some axle (ford 9") but you can't really replace with a stronger piece without getting a bigger r&p set, which requires a bigger housing... meaning you have to replace the whole axle.

If you want big tahrs then switch to some axles from a 1008

Don't forget the weak carrier, the relatively thin ring gear, and the oh so wonderful G80 "Grenade Lock" limited slip/locker abortion GM put in those axles. I've seen them all fail a time or two. Several times on relatively stock trucks.


Let's also not forget that Toyota tends to err on the safe side with their axles. The Tacoma's axles have weight capacity ratings damn near what GM puts under it's similar vintage half ton trucks and the pieces sure are beefier from everything I've seen. Used to annoy me to death that my buddy's '91 Toyota Pickup 4x4 had thicker gears than my '92 Blazer K1500.
Toyota trucks generally = beefy axles for their size.
GM half tons generally = barely enough to get the job done (since the late 70's).


Also keep in mind a 2008 GM half ton truck has nearly 3 times the power it had in the early 80's and it's rear axle is a relatively minor improvement over the original late 70's early 80's 10 bolt. It lives but you don't want to beat on it.

 

[hobie237]

Toyota (particularly in the case of the Tacoma) has taken a LOT of time to develop a good off-road truck. The entire 4WD driveline is overbuilt. There's a reason that the Taliban (among other, less well-known governments) uses Toyota trucks.

There are plenty of places where axles can fail. Ring and pinion gears can blow up. Differential units themselves can blow up (particularly the Gov-Bomb) in amazing ways. Axle shafts can snap. Universals/CVs can break.

As a general rule of thumb, bigger is better. It's easy (and fairly inexpensive) to slap a 14 bolt and D60 into a Blazer or other half ton.

Or you can just baby the thing around. For me, this is not an option. I don't even baby around my '95 Saturn daily-driven runabout. I don't abuse it, but I don't go easy on it, either. I don't have a turbo'd, lowered Miata to drive it slow, I don't have a 4x4 truck to baby it around on pavement. I just make sure that the vehicles are set up for the appropriate usage, that they can take what I can throw at them, and call it a day.