The dealership let me bring this truck home. It has 4WD but when in 4WD when I turn or back up turning the truck almost seems to act like its got the emergency brake on. Only when you go straight does it NOT drive like this. Is this the limited slip kicking in? My '02 4Runner doesn't act like this. Please help.

 

Not to spoil your thoughts on the Tundra but, be prepared for some crappy fuel mileage. Around 16-17 highway, and around 12 in town.

That's why I dumped my 04 Tundra. 4.7, 4speed auto, doublecab 4x4.

 

Any idea of when the truck acts like this when turning?

 

Do NOT put your truck in 4 wheel drive, on DRY PAVEMENT. I repeat do NOT do this. It is extremely bad for your drive train. What you just experieince is called binding. Bad for your axles

 

I went through the same thing when I bought my 1995 4x4 Toyota pickup truck 12 years ago. The front end binds because both front wheels are locked to the front axle and both wheels turn exactly the same number of revolutions. Therefore, on turns, there's lots of friction in the front tires. That's why you don't want to engage four wheel drive on dry pavement. Dirt is okay. Grass is okay. Snow is okay. Rain is okay, but only if you have to. Dry pavement is a no-no.

 

OH OH i guess i hope i didn't screw it up too much. I did it about 5 times less than 2 minutes to test and show the mechanic.

 

Your truck has 2 axles. On each axle there are 2 wheels. There is the front axle and it's 2 wheels, and the rear axle and it's 2 wheels. At the center of each axle is the differential.

The Job of the differential comes into play when you are turning and one wheel requires more revolutions to complete the turn (the outside wheel) compared to the other wheel which requries less revolutions to complete the turn (the inside wheel). The Differential detects lesser resistance in turns and it adjuts the power (revolutions) it receives from the transmission (and transfer case) through the drive shaft and essentially delegates it to the appropriate wheel on it's axle to complete the turn.

When you are in 2 HI, your rear wheels are powering the vehicle and your front wheels are just in for the ride so to speak. Since they are not engaged to the drive train, the differential is not doing anything with them and is not receiving any power really. But your rear wheels ARE receiving 100% of the engines power and delegating the power to the appropriate wheels thanks to the differential in the turn. So lets say as an example you make a left turn. On that left turn the right wheel say gets 75% of the engines power to make 75 revolutions (as an example) and the left side gets 25% of the engines power to make 25 revolutions (again, as an example). This completes the turn, you're driving in a straight line again, and power is now automatically adjusted by the differential to be given equally to each wheel on the rear axle so you can drive straight again and power the vehicle properly.

When you shift it into 4 HI, now 50% of the engines power is sent to the front differential/axle to and 50% of the engines power t the rear differential/axle. This ratio can NOT be adjusted. It's 50/50, period. No sending it back and forth between front and rear.

So now you have 2 axles powering the vehicle with their 2 wheels each. The problem then becomes the fact that each wheel, take different pathes. Your 2 front wheels and 2 rear wheels do not take the exact same pathes during a turn, so each actually makes a different number of revolutions. The 2 outside wheels still get the most revolutions/power, and the 2 inside wheels get the least power/revolutions thanks to the differentials, but the 2 outside wheels will differ from each other, and the 2 inside wheels also differ, because again, they take different pathes. So becuase of the traction for your tires not allowing one of the wheels to slip, and they are turning at different rates on the same side of the vehicle, you now have a recipe for what is called "binding." If the back left wheel is turning more than the front left wheel, then the black left wheel has to "give" or "slip" to become equal to the slower revoutions of the front left wheel in this turn. Do you get what I"m saying? If it can NOT slip, which is what would happen on dry pavement then it will cause the axle to bind, which is bad. But this is why it is adivsable to only use 4 wheel drive in situations where one of your wheels can slip in a turn. Say as mentioned wet gras, a bit of ice, some snow, mud, loose rocks, etc, etc.

Now looking at the above, you can probalby figure out that if you are driving in an exact straight line in 4 Hi or 4 Lo, all wheels will be being powered, but all in theory should be turning at the exact same rate (assuming you have all your tires inflated properly and equally and have the exact same tire height on all 4 wheels), hence you won't experience binding driving in a straight line.

Now the reason your 4runner didn't expierience binding is because it has another seperate differential between the front and rear differentials. Remember what I said above about the fact that the power is distributed equally between the front and rear drive shafts 50/50 and it can't change thsi ratio in a part time 4 wheel drive system (what you find in all Toyota trucks but not all Toyota SUV's). Well the 4runner you had, because it had the center differential, it can send power back and forth between the front and rear differential, which can compensate for the differences in wheel spin. All 4 wheels are still being powered, but the ratios of front to back can be automatically adjusted, so you won't expiereince any binding at all. Now if you locked the center differential, you now have the exact same system as the Tundra, which means 50 front/50 rear and you would expierience binding.

Now you're probably wondering why, would you want 50 front and 50 rear only. Why wouldnt' you want the 4runner system with a center diff in all of them. Well there are huge advantages to having 50 front and 50 rear offroad and not being able to send the power back and forth between the front and rear axles. The reason is offroad prowess.

If you are on a trail and your right rear wheel comes off the ground, your differential will think it is the outside wheel in a turn (because it senses lesser resistance) and the 50 percent of power the rear differential has will all be sent to that wheel spinning it aimlessly effectively negating the wheel which has traction, which has contact with the ground, which is the wheel you actually would prefer to have the power right? Well because your 2 front wheels still have 50 percent of the engines power, and they both have contact with the ground, you wont' have issues with the front differential sending it's power to the wheel in the air, and the front wheels will pull you out of the rut and get your rear wheels back on the ground.

 

Wow Coed. You sure do know alot. Thank you for explaining it to me. I really appreciate it.