Odd shift when going 60

[SiegSolara]

This just started happening a couple of days ago, dunno if anyone know what the problem is. Im driving an automatic.

When Im driving between 55 and 65 mph, periodically (seems like once every 3 minutes or so) I will feel a strange shift. You know that odd shifting feel you can get when you switch from reverse to drive (or vise versa), feels like the car shifting hard. Anyways, thats what it feel like when Im going 60 mph.

Also, I hear this bearing noise (pulsating humming) coming from the front of the car between 50-60 mph. I've replaced the front left and front right bearings, but it still makes that noise. A mechanic said there is another bearing located on the driveshaft (which I assume is near the transmission).

Could the two problems (the periodic shift and the humming noise) be related to a driveshaft bearing going bad?

Thanks

[RichD978]

i had the same weird shift but it was any speed. i flushed the atf and it was a lot better

[SiegSolara]

I'll change the fluids this weekend and see if the problem still occurs.

Thanks!

[SC V6]

could be the overdrive clutches slipping... happened to me

[DDH1313]

This is very far fetched but it is my theory..... if the bearings that were replaced are faulty and are intermittantly grabbing I can see how that would happen. The transmission would not know the difference, having determined that more torque was required to turn the driveshaft and thus dropping out of converter lock-up momentarly and then shifting back into lock-up. "Same as if you went up a slight hill". Do your RMP's increase slightly when this happens and then fall back?? I guess that is one important question.

[RichD978]

"Same as if you went up a slight hill". Do your RMP's increase slightly when this happens and then fall back?? I guess that is one important question.

i think that still happens to my car. what causes it? what needs to be fixed and how. and also how much? thanks

[DDH1313]

"Same as if you went up a slight hill". Do your RMP's increase slightly when this happens and then fall back?? I guess that is one important question.

i think that still happens to my car. what causes it? what needs to be fixed and how. and also how much? thanks

I guess that first we need to make sure that we are defining a problem and not normal operation. The idea behind a lock up torque converter is to increase gas milage by slowing engine RPM. This is accomplished by a clutch inside the torque converter itself that "locks up" when the torque required to maintain a particular speed is less than what the engine is capable of creating "there are other factors as well such as vehicle speed and engine tempurate but we wont go there"...... Now, having said all that. If you accellerate from a dead stop you should be able to feel 5 distict inistances of the tranny doing something. The first 4 are the shift themselves of the gears. The 5th is converter lock up and is actually sometimes difficult to feel due to the quality of our cars. I suppose its possible that over time either.... A) the shift into/out of lockup becomes more prevelent due to normal wear and tear and thus is being noticed but was always there or B) something is causing this process to happen at unintended times. This should be occuring in cases where you are asking the engine to put more torque to the ground than what it is capable of delivering while in lockup...IE going up hills, accelerating but not so much that it drops into 3rd gear, in some cases if you have cruse control on and press the toggle up to accelerate it will drop out of lockup. Oh Yeah... and most obviously, if you press the o/d "over drive" off button. The RPM variation between lockup and non lockup is not much. Maybe 3 or 4 hundred RPM?? unless anyone knows better. If your car is performing the task during sitautions similar to what i have mentioned than it is doing what it is supposed to and nothing is wrong. If it is doing it outside of what is normal, or to often then either something is wrong with the electronics or mechanics of the tranny. Hope this helps.

[SiegSolara]

I just got the tranny fluid flushed, and theres no real difference. I think that the shift may be due to the slippery weather. Seems to only happen just after its snowed. Wonder if traction control could be to blame?

[00-solara]

I have a double like down shift when going around 50 at 2,000 rpms but thats about it is that what you are talking about

[SiegSolara]

It hasnt been shifting for the last week or so. Incidentally, the weather hasnt been snowing or icing for the last week or so either. I think it was the traction control.