Why does the front tires not spin when in 4x4

[travis0311tide]

I haven't had my 4runner but a few months and it has done very well on clmbing hills and going in snow with no problems at all. Today was the first day I needed to use it in the mud and really had to get on the throttle hard. The back tires would spin and throw mud but the front tires never spun. Needless to say I got stuck because the front tires would not spin..I put it in 4 high and 4 low but no change. Does Toyata have something about them that prevents the front tires from spinning in the mud? I'm very displeased if this is the case.

 

[Gecko123]

I haven't had my 4runner but a few months and it has done very well on clmbing hills and going in snow with no problems at all. Today was the first day I needed to use it in the mud and really had to get on the throttle hard. The back tires would spin and throw mud but the front tires never spun. Needless to say I got stuck because the front tires would not spin..I put it in 4 high and 4 low but no change. Does Toyata have something about them that prevents the front tires from spinning in the mud? I'm very displeased if this is the case.

Did you lock the differential?

 

[travis0311tide]

Did you lock the differential?

Yes, I locked it in but it made no difference.. I have never had a Toyata before so I thought maybe this is the way they are made. Doe's your front tires spin? Mine had no spinning. Once I got out of the mudhole and went n up the hill it pulled good but if the back tires ever started to spin I was stuck again.

 

[Gecko123]

Yes, I locked it in but it made no difference.. I have never had a Toyata before so I thought maybe this is the way they are made. Doe's your front tires spin? Mine had no spinning. Once I got out of the mudhole and went n up the hill it pulled good but if the back tires ever started to spin I was stuck again.

That's odd. with it locked all four wheels should get equal power, from what I understand, so to prevent being stuck.

 

[DocMT]

Sounds like you weren't in 4wd. I'd check to make sure your 4wd system is operational. ATRAC will step in to control a spinning wheel (front or rear), but it should still spin until ATRAC is activated.

 

[jlmilligan]

That's odd. with it locked all four wheels should get equal power, from what I understand, so to prevent being stuck.

That is only partially true. You are locking the center differential only. Which means equal power to the front and rear. NOT equal power to all 4 wheels. 50% to the front 50% to the rear. So one in front and one in the back should be turning. You would need front and rear lockers for that.

I would say that something isn't right. When you put it in 4hi AND lock the center diff, what lights come on and what lights flash?

 

[DocMT]

That is only partially true. You are locking the center differential only. Which means equal power to the front and rear. NOT equal power to all 4 wheels. 50% to the front 50% to the rear. So one in front and one in the back should be turning. You would need front and rear lockers for that.

I would say that something isn't right. When you put it in 4hi AND lock the center diff, what lights come on and what lights flash?

Well, that's not entirely accurate either. Yes, locking the center diff will get you 50% power sent to the front and 50% to the rear, but to say that only one front and one rear tire would be turning (or spinning) isn't really true. ATRAC will brake a spinning wheel, which will transfer torque to the other side. So all wheels will turn/spin when you're in 4wd with the center diff locked. And in a case where the traction is equal between the front wheels, both tires will turn because they'll both get equal torque from the engine. Same is true for the rear wheels.

 

[jlmilligan]

Well, that's not entirely accurate either. Yes, locking the center diff will get you 50% power sent to the front and 50% to the rear, but to say that only one front and one rear tire would be turning (or spinning) isn't really true. ATRAC will brake a spinning wheel, which will transfer torque to the other side. So all wheels will turn/spin when you're in 4wd with the center diff locked. And in a case where the traction is equal between the front wheels, both tires will turn because they'll both get equal torque from the engine. Same is true for the rear wheels.

True, however, if the ATRAC is engaging, then one wheel is not getting traction. So it applies the brakes to that wheel. ATRAC will stop the loose wheel from turning, thus providing power to the other wheel, not by locking the axle. It is a very good system, but it isn't an axle locker. According to the statement that I quoted,

Originally Posted by Gecko123
That's odd. with it locked all four wheels should get equal power, from what I understand, so to prevent being stuck.

All 4 wheels can and will have power, but it won't be quite equal and it doesn't mean that one wheel can't stop completely. It is trying to equal the speed of both wheels so that they get equal power. If all 4 wheels truly got EQUAL power, then one wouldn't slip in the first place.

That is also why I think that something isn't right. Either the ATRAC is acting up or the center diff isn't engaging or something else isn't right. IF the CDL isn't engaging, the light should be flashing. The light on the dash should be on solid for it to be engaged.

 

[DocMT]

True, however, if the ATRAC is engaging, then one wheel is not getting traction. So it applies the brakes to that wheel. ATRAC will stop the loose wheel from turning, thus providing power to the other wheel, not by locking the axle. It is a very good system, but it isn't an axle locker. According to the statement that I quoted,

Originally Posted by Gecko123
That's odd. with it locked all four wheels should get equal power, from what I understand, so to prevent being stuck.

All 4 wheels can and will have power, but it won't be quite equal and it doesn't mean that one wheel can't stop completely. It is trying to equal the speed of both wheels so that they get equal power. If all 4 wheels truly got EQUAL power, then one wouldn't slip in the first place.

That is also why I think that something isn't right. Either the ATRAC is acting up or the center diff isn't engaging or something else isn't right. IF the CDL isn't engaging, the light should be flashing. The light on the dash should be on solid for it to be engaged.

ATRAC uses the same wheel speed sensors that are used for ABS. So yes, ATRAC can react very quickly to a spinning wheel. It will brake/release/brake/release fast enough that both front or both rear tires will get torque almost simultaneously. If you've ever seen a video of a 4Runner struggling for traction in snow, then you've most definitely seen ATRAC in action. It's very similar to ABS, but in reverse. Instead of releasing a locked wheel (like ABS) it brakes a spinning one. But my point is simply that both front tires and both rear tires should be spinning/turning when you apply power in snow. If the OP isn't getting the front tires to spin at all, then something is definitely very wrong. It soundsl like he's not actually in 4wd.