Is this a simple question ?

On the 2008 2 wheel drive with the locking diff. it says not to drivre over 5 MPH. Why can't you just peddle it through the gear box ?

 

I'm confused also....

When you have 4WD and are in 4lo range - they tell you not to drive more than 5mph (or something like that).

But in 2WD? Baaahumbug!

 

i could be wrong, but i think it is because cornering or turning at high speeds can be dangerous with the back locked. The binding can cause the truck to flip easier. not sure if this is the reason but it made sense when it was explained to me

 

Also, cornering with the locker on can cause damage to the diff. While cornering the tires rotate at different speeds - the outside tire rotates faster. So when you lock the diff, your tires are unable to rotate at different speeds. That's why you shouldn't go more than 5mph with the diff locked.

 

Then why doesn't Toyota build a failsafe circuit into the locking diff system to dis-engage at speeds over 6 MPH???

If a Toyota car's rear defoster turns off automagically after 10 minutes, then the electronic diff should dis-engage when speeds reach 6 MPH.

 

I understand the binding aspect of it....

The fact the 2WD guys can engage the locker anytime and the 4WD guys can't - is the confusing part to me. I mean - I can't imagine what they were thinking. Is there really any difference ?

 

that i'm not sure about. that confuses me too. i dont know why it would be ok for a 2wd to engage the locker, but a 4x4 in 2wd cant. No idea what toyota was thinking when they decided that made sense.... You're one of our resident wheelers, with all the answers, i'm actually surprised you dont know

 

drive with the diff locked as fast as you want to, nothing bad will happen. just dont run it locked on pavement, as that is where there would be too much strain on it and something may break, or you could wreck. i've had my diff locked and ran it up around 40-45 mph on dirt/grass and it was fine......kinda fun actually.

toyota only says dont run it over 5 mph while its locked for liability reasons....basically to save their own ass.

 

thats what i thought, thanks

 

OK, but I have friends who are into drag racing. They've got built hot rodded but streetable Camaro's and Roadrunners.

They install Posi to prevent it from "peg legging", where only one wheel turns, and the other is left to slip.

They want both wheels to turn. They're exclusively on the street. So, how come they/their cars can do it.

I see them go around corners and all I see is chirping. Not arguing here, just trying to get to the bottom of this.

 

the only thing i can really say here is dirt and grass give alot more that pavement or asphalt does. plus it may be a big variance with their tires.....all terrrain tires on a truck are way different that slicks or street tires on a car set up for racing.

 

Thanks for explaining Posi! I always thought it was the same as a locked axle.

I'm with Tacomaman. Trucks and cars have had lockers for years, but mostly for racers or offroaders who KNOW what to expect. Put one in a truck that any schmuck can buy without knowing how it works could spell trouble. Toyota doesn't want to get sued cuz some idiot locked up and power slid around a corner into a bus load of kids. Even Detroit lockers could do that from what I understand. Heard some guy talking about how he'd get on the gas going around a corner. The locker would engage with a BANG, scare the crap out of the people on the sidewalks, and light up the tires!

And I second the comment to bite your tongue about Toyota auto-disabling it above 6mph!! I've used mine at 35-45mph on snowy roads to help hold the truck straight. It would fishtail slightly in 4wd cuz my tires suck and one would spin. With the locker on at least both tires spun equally fast and the truck didn't try to break loose. There was lots of snow/slush on the roads so binding wasn't a problem. If toyota interfered then I'd have to disable yet another nanny system to do that.

 

some of my buddies that have full blown locker rear ends on their pre runners,
drive the shit out of em' on all types of road surfaces.
On tighter turns the tires chirps.

????????

 

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These are still not (most likely) spools, but gear or clutch types that are not totally street friendly, but do allow some varying speeds between the L and R axles.

 

awesome explanation mjp!!!!