question about 4x4 and locking differential

Even though you have open diffs, running in 4wd on pavement is hard on the drive train, because you have a solid drive train between the front and rear diffs. There is no slip in the transfer case from front to rear. You still have a different turning radius between your front and rear wheels, meaning the front wheels turn at a different rate than the rear while turning and something must give somewhere to allow for the difference. Since you have no slip or clutch in the transfer case (I think that is what they meant by center differential)to allow slip between the front and rear wheels, either the tires must slip on the pavement (which is why you hear the wheels slipping in dirt when you turn while in 4wd) or the drive train must give (very bad and expensive noises coming from underneath). Open diffs and limited slip diffs allow slippage from side to side, but not front to rear.

That being said, my Toyota manual says nothing about not running 4wd on hard surface. It simply says to run in 4wd at least 10 miles per month to keep the system lubricated. If there were a problem I would suppose they would state so. Now, I must ask, why would you want to run 4wd on the pavement anyway? It puts stress on the drivetrain, engine, and tires, wastes gas and horsepower, and has no practical application that I can think of, other than to keep the system lubricated, as stated above. If you have oversized tires, you could actually break things in your drivetrain by going 4wd on hard surfaces. Some kids like to light up all fours (spin the tires) to show off, but I guess I've grown out of that from paying for my own vehicles, gas, maintenance, and tires for too long.

 

Thank you for clarifying this for me!

 

Thank you for your detailed explanation. I now get it!

 

Center differential is key to hard pavement "all-wheel drive". This is also a MAJOR difference between AWD systems (All-Wheel Drive or Full-Time 4-Wheel Drive like on a Subaru or a RAV4) and 4WD systems (Part-Time 4-Wheel Drive like on a truck like the Tacoma).

 

Incorrect. 4x4 means all 4 wheels get drive line power. They will continue to operate normally. If you have limited slip they will slip if you dont, they wont. I use 4x4 all the time on the freeway when it gets slippery or wet. Toyota limits the speed to either 55 or 65 I cant remember but its written on the sun visor. Other companies do not have these limits. Its because of the way the system is made as others have said. awd vs 4wd

you must be in 4 lo to engage the rear lock. Both rear wheels spin at the same rate and both have drive line power. It will be more difficult to turn sharply because when you turn the inner wheel spins more slowly than the outer wheel. When the rear is locked, a sharp turn will cause the inner wheel to hop because it is being forced to turn at the same rate as the outer. For this reason it is dangerous to have a locked rear end at higher speeds. It can cause a vehicle to flip at high speeds.

4x4 just means 4 wheels get power. locked means wheels spin at the same rate. technically, 4x4 locked would be front wheels get power and the rears get the same amount of power... like 3 wheel drive. Front wheels do not lock in the taco.



Why do you want locked wheels? traction control works with the brakes. If a wheel is spinning faster than the rest, the traction control activates the brakes to slow the spinning wheel down with the assumption that at a slower rate it will gain traction. If you are in mud, it will never get traction so eventually it would be completely braked. the idea is for the wheel on the other side to gain traction and move the vehicle out of the area. There was a problem with the Audi TT where the traction control was so sensitive that it could actually get stuck in 1/2 inch of snow if all 4 wheels were spinning. the traction control would brake all 4 wheels to the point that is stalled!

With a limited slip... as one wheel spins faster, the brakes brake the wheel and the limited slip transfers power to the other wheel. Now this one wheel has all the rear end power and the likely hood that it will begin to spin is greater. which means that the traction control would begin to brake the wheel because it is spinning. So now you have on stuck spinning wheel and one wheel with all the power spinning that the traction control is braking when you actually want it to have power to pull you out. This is a rare situation on road, but likely to happen off road. Land rover actually had a button to turn off traction control for this exact reason. Locked rear end prevents this. It causes both rear wheels to get the same amount of power and causes them both to spin at the same rate. Toyota's locking system deactivates traction control to ensure that it happens this way.

Limited slip is generally better on road because it aids the wheels in getting proper power for on road situations. Locking is generally better for off road crawling and climbing situations. Limited slip is generally better faster movement and locking for slower. The TRD off road 4x4 does not have limited slip. The sport does but the sport does not have lockers.

If you put a locker on the front, now you are forcing both front wheels to spin at the same rate. Think about climbing over a rock obstacle. If one wheel is in the air, you dont want it to be spinning freely or braking.. You want it to be steady so when it gains contact again, it wont jerk the truck. You also want it to have power so that when it does come in contact with something, it grabs it and climbs.

 

A more fun and faster way to tell is to peel out and leave some rubber on the road and see if you have one trail or two. If you just have one rubber trail, you have limited slip

 

i think everyone is getting a little crazy about this topic a locker helps you off road

 

So I have an 09 OR TRD Prerunner. When the locker is not engaged, is my rear diff open or LSD?

 

Open. IIRC....The Auto LSD is not a differential- It's a computer that controls the brakes.

I'm pretty sure that you truck has the Auto LSD with an open rear diff with the electronic locker.

 

Thanks. I guess I'd have been better off with the Sport LSD rather than the OR Auto LSD then.

 

Anyone ever see a chevy z71 locker in action? My old man has one and I thinks it's pretty nice, turns on automatically, works in 4HI, and gets him through the mud with HT tires. Wish I could get one on my TRD sport.

 

IIRC- All the 09 models are Auto LSDs...There is no more mechanical LSD in the Tacoma.

You can get a "lunchbox" locker that'll auto lock...or replace the sport LSD with a ARB Air Locker for switchable locking...LOts of options.

 

Well I wont hi jack this thread, when the time comes to research this, I'll keep you in mind. Thanks Brunes

 

i tried rear diff lockers on my 02 TRD, i tried 4H , and 4L...light just blink,, thats it. owners manual said, when light is solid thats when lockers are engaged.

 

If your locker hasn't been used in a while it may be stuck. It will only engage while in low-range, unless you have done the "grey wire mod". Also, it will not engage while you are stopped. The light blinks when you push the button, indicating it is trying to engage, but if you are stopped, or if you are not in low-range, it will just blink. Once you start rolling it should engage and the light should go solid, indicating the diff is locked. With your window down you can hear it engage. It's electrically activated, so you might check your wiring at the diff. It may be that the solenoid is just stuck.

I bought my 2000 with 120K on it in '97. The first time I tried to use the locker it would not engage. Apparently the previous owner never used it. It took a few minutes driving around with the light blinking before it finally engaged. I try to use it once or twice a month, at least to engage it, to keep it lubed up.