what happens to steering when towed? 5

[knowlittle]

Someone please explain how this happened.

I towed a front-wheel drive vehicle on a tow dolly. Front wheels were up on the dolly, and gear was in Park. At the destination, I noticed the front wheels were turned (as if the steering wheel had been turned). It must have happened when I turned corners.

I started the engine, turned the steering wheel to straighten the front wheels, drove the vehicle off the dolly, and parked it in the driveway. I expected the steering wheel would remain turned when front wheels were straight. Not at all. Both the front wheels and the steering wheel were straight! How did this happen?

 

[gt6racer2]

The wheels are mechanically linked to the steering wheel, so if one moves, then so does the other. The wheels can turn the steering wheel just as the steering wheel can turn the wheels. I suspect you intended to state that on the dolly the wheels were turned but the steering wheel was straight(upright), but then when you came off the dolly the wheels and the steering wheel were now both straight (upright). This can happen as the steering wheel turns more than one full turn in each direction, so the wheel can be straight(upright) both steering straight ahead, but also in a sharp turn.

 

[LionelHutz]

Do you mean the steering wheel lock was engaged? Likely there was enough force on the steering it forced the lock to slip.

 

[knowlittle]

Clarification: On the tow dolly, the front wheels were turned, but the steering wheel remained locked (upright), apparently because the gear was in Park.

Actually, I towed 2 cars in the trip. I towed Car 1 to the destination, and towed Car 2 back home. Both cars had front wheels turned (with steering wheel locked upright). But when I unloaded the cars off the tow dolly, both cars got both front wheels and steering wheels straight.

I wonder if hydraulics has something to do with this self-correction?

 

[Tmoose]

"the front wheels were turned, but the steering wheel remained locked (upright)"

If this is really what happened, i think something is broken.

 

[MikeHalloran]

The typical steering lockplate is retained by a snap ring and a spring, which makes it difficult to remove the snap ring without using a special tool to depress the lockplate and compress the spring.

The spring is present so that you can turn off the key with the steering wheel in any position, and the lockplate notches will engage with the locking bar when the steering wheel happens to be turned so the notches align with the bar, perhaps later.

As a side effect of that feature, the lockplate can deflect and snap off of the locking bar when the wheels backdrive the steering against the lock. Call it a soft failure mode. It may deform or fracture some of the parts, so the locking mechanism may feel/work differently, or not lock at all, after a tow.

That's why I now rent trailers instead of dollies.


Mike Halloran
Pembroke Pines, FL, USA

 

[LionelHutz]

You may also want to take a look at the steering system of both cars just to ensure nothing got bent or damaged. Another test would be to more the steering to full lock in each direction and ensure the wheels turn the same amount each way.

 

[knowlittle]

Thanks. When I get home, I will check for something bent, cracked, or warped. I suppose I will be looking at the end of the steering column in the engine compartment, right?

As I think about this, I remember how difficult it was for me to unlock the steering wheel after towing. This time I towed a much longer distance and more turns.

By the way, what must I do differently with the locking mechanism damaged? Have it repaired? Just be aware of it? Apply foot brake always? Junk the car? Thanks.

 

[MikeHalloran]

The locking mechanism is inside the steering wheel end of the steering column. You have to remove the airbag and the steering wheel to get to it.

AIRBAGS CAN KILL YOU.

Don't mess with this stuff unless you know how to disarm the airbags. It's explained in the shop manual, which you should definitely have before proceeding to DIY. You can buy the special tools from JCW, or some auto parts stores. Read the manual and study the pictures.

Or engage a professional.
An old cranky one can probably guess what it will cost to repair it after personally inspecting it, and discuss your other options, better than we can from here.







Mike Halloran
Pembroke Pines, FL, USA

 

[cibachrome]

No mystery here. No bent parts, lock plates, or snap ring involved.

The hydraulic control valve in the steering gear has mechanical detents at about +- 3 to 4 degrees so that in the event you loose engine power, steering hose or belt, you can still control the front wheels with the mechanicla connections to the steering wheel. Normally, with the engine running and the hydraulics pressurized, the compliance in this system is pretty small. However, with the engine off, even small steering loads from cornering or turning your dolly will rotate the unpressurized valve body and there will be a large angular deflection between the steering wheel and the road wheels. If your steering gear ratio was let's say 16:1. then that 3 to 4 degrees could produce about 48 to 64 degrees at the road wheels. This is quite visible

One could argue that the tire aligning moments would be expected to encourage the road wheels to return back to center, but a few bumps along the way would relax these moments and the relationship would add up to be skewed. The wheels were probably turned in the direction for which you made the most number of turns and hit the most road bimps, eh?

Try the same experiment with and without the motor running. You only need to drive around a roundabout a few times for this to evolve...

 

[knowlittle]

1) Thank you all for answering my question. I posted the question at my favorite auto repair forum, but none could answer it.
2) Indeed I can turn the steering wheel in PARK without key in. (I cannot pull the gear out of PARK without key in.) Obviously, the steering lock plate is broken. I will address this at the repair forum, for I have no intent to turn this engineering forum to a repair forum. Thank you again.
3) I put the car on jack stands and turned the engine on. Steering wheel turned 1 1/2 turns both left and right.
4) I am a decent weekend mechanic. I have dealt with steering wheel, airbag, horn, etc. Many years back, a neighbor asked me about her car problem. I said to her I didn't know much about cars. She said, "But, aren't you an engineer?" I wonder if that statement got me into car repair.

 

[LionelHutz]

cibachrome - you are trying to tell us that with the engine off the wheels can turn 48 to 64 degrees without the steering wheel being turned? I haven't met a car yet where that is true.

knowlittle - thanks for coming back and confirming the problem. You could drive it as is, the concern would be that the damaged piece could jam up the steering while driving the vehicle.

 

[cibachrome]

No ! We were just seeing if anybody was really paying attention... (Unless its an older Dodge without a t-bar in the valve body or maybe a John Deere tractor).

 

[knowlittle]

the concern would be that the damaged piece could jam up the steering while driving the vehicle

You scared me enough to give the lock plate repair a high priority.