I have also experienced this. Last year a few times before I figured out what the problem was and once this year because I forgot.
When the road is icy or even hard packed snow there is limited traction. If you apply the brakes gently the fronts will hold much stronger than the rears. The car is a rear wheel drive bias so it is sending more power to the rear wheels and the engine can over power a light application of the brakes on a slippery surface. I have had it happen several times before I figured out what was happening. If you press harder on the brake pedal when stopped it will lock the rear wheels.
I was able to figure this out from old school experience. Cars with carburetors in cold weather with the choke on are raving faster at idle. Older cars commonly had rear drum brakes that were weaker than front discs and were more commonly rear wheel drive. The car would be revving at a stop and the rear wheels would be spinning. A car with an open diff would start to slide sideways in the rear just like my Stinger GT with an open diff. After this happens a few times I start to think "Hey that's just like the cars in the old days" and then it clicks that the rear wheels are turning on the slippery road. So the next time it happens I press a little harder on the brake and presto! it stops.
As for the engine revs increasing the most likely culprit is your right foot is just slightly contacting the gas pedal especially if you have large feet. When the car starts unexpectedly moving forward you instinctively press harder on the brake but also press harder on the gas until you adjust your foot on the pedal.
My advice to anyone is to pay close attention to exactly what you are doing when this happens. Ask yourself is my foot on the gas? Am I pressing the brake hard enough when stopped?
Yup. This happened to me the other day. Fronts were on snow, rears on ice at a stop light. I felt this odd sensation coming from the rears. At first, I was wondering what the heck was going on and then I figured it out.
This happened to me as well last year after an ice storm. Was trying to move the car from the slab spot next to our garage (on an alley) into the garage. Alley was all ice. Ended up almost hitting the garage as I was at full steering left trying to turn into the garage, but feathering the brake to go slow, and the car was just understeering straight as the rears were still getting power but the fronts were locked.
Ended up throwing it in nutral and coasting. I'm so use to manual cars with a clutch that I was completely unprepared for it.
Determined that if you are on Ice, with the car in drive and your foot FIRMLY applied to the brake pedal, the right rear wheel will continue to rotate. It doesn't matter how hard you press the brake pedal.
I figured this out when my wife was trying to get into the car on my Icey driveway, she was yelling at me that rears were rotating.
This tracks with what I have experienced before, if you're on ice the car wants to crawl and pushes the front to the left. The only solution is to shift to neutral.
Determined that if you are on Ice, with the car in drive and your foot FIRMLY applied to the brake pedal, the right rear wheel will continue to rotate. It doesn't matter how hard you press the brake pedal.
It's done this since new, as others have reported in this thread. If I had to guess, the open diff on the NA models is sending all the torque to the right rear, the brake bias just isn't high enough to prevent the rotation.
It's done this since new, as others have reported in this thread. If I had to guess, the open diff on the NA models is sending all the torque to the right rear, the brake bias just isn't high enough to prevent the rotation.
It's done this since new, as others have reported in this thread. If I had to guess, the open diff on the NA models is sending all the torque to the right rear, the brake bias just isn't high enough to prevent the rotation.
This tracks nearly perfectly with the behavior of a seized / sticking caliper. Your right rear wheel should not rotate at all with the brake pedal pressed, while in drive, with the gas pedal NOT being pressed.
The brake have more than enough power to stop the wheels of a stationary car that's idling in gear/.
I would be concerned.
Another scenario could be that the brake fluid is old, and is moisture saturated which allowed the fluid to freeze/gel up significantly. What's the age of the fluid?
Technically brake fluid can't freeze solid like water due to the fact that it is an oil. But it can reach a point where it becomes so thick that it no longer becomes effective at transferring force from the master cylinder to the wheels. The fluid can “gel” or congeal.
It's not enough to just say that the car has an open diff. For a tire to spin, your torque converter at idle would have to be transmitting more torque than your brake is resisting, which seems much less likely than that particular brake not working / not working properly.
One test you could do is to jack the rear up and brake until one or both tires stop spinning. If only one stops spinning, keep braking further to see how much more brake pressure it takes. Or apply the brake in neutral while someone tries to spin each wheel, and see if the culprit is getting much less braking.
It's not enough to just say that the car has an open diff. For a tire to spin, your torque converter at idle would have to be transmitting more torque than your brake is resisting, which seems much less likely than that particular brake not working / not working properly.
One test you could do is to jack the rear up and brake until one or both tires stop spinning. If only one stops spinning, keep braking further to see how much more brake pressure it takes. Or apply the brake in neutral while someone tries to spin each wheel, and see if the culprit is getting much less braking.
I'm not the only one experiencing this issue. It's literally the subject of the thread.
I posted my observation to validate what others in this thread have experienced.
I'm not the only one experiencing this issue. It's literally the subject of the thread.
I posted my observation to validate what others in this thread have experienced.
I'm not the only one experiencing this issue. It's literally the subject of the thread.
I posted my observation to validate what others in this thread have experienced.
I'm not saying it's not happening, I'm saying that an open diff alone is not the cause. Either the TC is sending way too much torque at idle, or a brake is clamping way too weakly / not at all. Checking how it behaves with both rear tires in the air should help diagnose.
I'm not saying it's not happening, I'm saying that an open diff alone is not the cause. Either the TC is sending way too much torque at idle, or a brake is clamping way too weakly / not at all. Checking how it behaves with both rear tires in the air should help diagnose.
Our traction control doesn't send any torque..... Our traction control only applies more BRAKE to the spinning wheel(s) - without adding any torque.
In this case we are talking about a car at idle. There is no torque vectoring/traction control at idle.
Is the car in question AWD? or RWD? - probably don't wanna be lifting just the rear of an AWD car.
Our traction control doesn't send any torque..... Our traction control only applies more BRAKE to the spinning wheel(s) - without adding any torque.
In this case we are talking about a car at idle. There is no torque vectoring/traction control at idle.
And I'm done with this thread. I've reported what I observed.
It matches the OP's use case. It matches what I've experienced first hand when the car was new.
I only posted this because I had a similar experience on ICE to the OP, and my wife's observation that the rear wheel was turning validated that experience.
If you're reading this thread and you experience the same I suggest that you shift to neutral until you're ready to move off again.
