[Wideopen93]

My 05 tacoma 4wd.... when 4wd is engaged it immediately pulls to the left... to the point where I have to counter steer to the right to keep me going straight... in 2wd it does just fine. The tire pressure is good (which would be an issue in 4 or 2wd if it wasn't) and it has just had an alignment done. I have had it on a rack with it running in 4wd, both front wheels turn and the steering wheel stays straight, so it appears to only be an issue when under a load. I have looked all over the web and can't find someone with even the same issue.

 

[Enola Gaia]

(1) Welcome to CT!

(2) The 2 clues we have to go on are that it only happens in 4WD and only when the wheels are on the ground and the truck is moving. Given these clues ...

There are 3 theories that come to mind, and they may or may not be entirely independent of each other.

Theory A: Brake / ABS Weirdness

This one is simple - for some reason the left front brake is dragging. I don't know why the brake would drag only in 4WD and / or on the ground, but it could result from one or both the following 2 theories ...

Theory B: Front Left Drive Components (Differential / Axle / Maybe Wheel)

This theory focuses on the front left drive engagement from the front diff out to the wheel. If there's something like a bearing going bad (whatever) anywhere from the diff out to the wheel it could cause a bind that you feel as a pulling to the left in 4WD. The fact that it only happens when it's on the ground tends to suggest something somewhere along the left front drive axle, but that's not a sure bet.

Theory C: VSC / TRAC (Stability / Traction Control System)

If your Taco has the VSC / TRAC system, it uses the ABS system to juke the pressure on any / all 4 brake units in response to signals from sensors at each wheel. If your left (or maybe even the right) front sensor is signaling the controller that something's locking / dragging / slipping, the controller might be attempting to correct for apparent slippage / locking by juking the left front brake. It could be a bad sensor, a wiring / connection glitch, a crazy controller, or some mild dragging of the sort that might be caused under Theories A and / or B above.

Those at the 3 possibilities that I can offer off the top of my head. Then again, I could be totally wrong.

I'd start with Theory C (VSC / TRAC weirdness). If the stability / traction stuff checks out fine, I'd move on to the left front drive axle (and connections on both ends). You may not be able to totally rule our Theory B until the front differential is checked out as well.

Hope this helps ...

 

[Wideopen93]

(1) Welcome to CT!

(2) The 2 clues we have to go on are that it only happens in 4WD and only when the wheels are on the ground and the truck is moving. Given these clues ...

There are 3 theories that come to mind, and they may or may not be entirely independent of each other.

Theory A: Brake / ABS Weirdness

This one is simple - for some reason the left front brake is dragging. I don't know why the brake would drag only in 4WD and / or on the ground, but it could result from one or both the following 2 theories ...

Theory B: Front Left Drive Components (Differential / Axle / Maybe Wheel)

This theory focuses on the front left drive engagement from the front diff out to the wheel. If there's something like a bearing going bad (whatever) anywhere from the diff out to the wheel it could cause a bind that you feel as a pulling to the left in 4WD. The fact that it only happens when it's on the ground tends to suggest something somewhere along the left front drive axle, but that's not a sure bet.

Theory C: VSC / TRAC (Stability / Traction Control System)

If your Taco has the VSC / TRAC system, it uses the ABS system to juke the pressure on any / all 4 brake units in response to signals from sensors at each wheel. If your left (or maybe even the right) front sensor is signaling the controller that something's locking / dragging / slipping, the controller might be attempting to correct for apparent slippage / locking by juking the left front brake. It could be a bad sensor, a wiring / connection glitch, a crazy controller, or some mild dragging of the sort that might be caused under Theories A and / or B above.

Those at the 3 possibilities that I can offer off the top of my head. Then again, I could be totally wrong.

I'd start with Theory C (VSC / TRAC weirdness). If the stability / traction stuff checks out fine, I'd move on to the left front drive axle (and connections on both ends). You may not be able to totally rule our Theory B until the front differential is checked out as well.

Hope this helps ...

Wow.... these are awesome suggestions. No one has come even close to mentioning something like Theory C. I keep getting things like maybe it is torque steer or the ADD system.... which neither makes sense.

So get this.... When I get on the brakes harder then just a super light amount the truck wants to pull to the left. I just figured great.... I have a right caliper that is going bad now too, which still could be the case, but maybe it has something to do with Theory C. I will look into it and will report back.

 

[Wideopen93]

Wow.... these are awesome suggestions. No one has come even close to mentioning something like Theory C. I keep getting things like maybe it is torque steer or the ADD system.... which neither makes sense.

So get this.... When I get on the brakes harder then just a super light amount the truck wants to pull to the left. I just figured great.... I have a right caliper that is going bad now too, which still could be the case, but maybe it has something to do with Theory A or C. I will look into it and will report back.

 

[Enola Gaia]

Just so we're clear about this ...

If you press the brakes it pulls harder to the left, but it's pulling to the left all the time even when your foot's off the brakes - right?

If it pulls left only when you're applying brakes (no matter how softly or hard) start with Theory A. If it's as simple as a brake problem that would probably be the easiest and cheapest to fix.

I'd be surprised if it's only one or the other front brakes, because I can't figure out why a brakes-only problem would only occur while in 4WD.

If it pulls left all the time (but gets worse when brakes are applied) you may have more than one problem (one of which is probably Theory A).

 

[Wideopen93]

Just so we're clear about this ...

If you press the brakes it pulls harder to the left, but it's pulling to the left all the time even when your foot's off the brakes - right?

If it pulls left only when you're applying brakes (no matter how softly or hard) start with Theory A. If it's as simple as a brake problem that would probably be the easiest and cheapest to fix.

I'd be surprised if it's only one or the other front brakes, because I can't figure out why a brakes-only problem would only occur while in 4WD.

If it pulls left all the time (but gets worse when brakes are applied) you may have more than one problem (one of which is probably Theory A).

Turns out I do not have VSC/Traction Control... and it only pulls to the left when braking in 2WD.

 

[Wideopen93]

Just so we're clear about this ...

If you press the brakes it pulls harder to the left, but it's pulling to the left all the time even when your foot's off the brakes - right?

If it pulls left only when you're applying brakes (no matter how softly or hard) start with Theory A. If it's as simple as a brake problem that would probably be the easiest and cheapest to fix.

I'd be surprised if it's only one or the other front brakes, because I can't figure out why a brakes-only problem would only occur while in 4WD.

If it pulls left all the time (but gets worse when brakes are applied) you may have more than one problem (one of which is probably Theory A).

I'm going to be working on it this weekend.... I will let you know what I find out.