Transmission/Electronics Question--intermittent clunky shifting

[cwillard59]

'03 SR5, V8, 90k miles--Intermittently, the following problem is occuring on my 4Runner. Upon startup, the check engine light comes on followed by the VSC and VSC Off lights. When these are illuminated, my automatic transmission shifts very hard through gears (jolting, not smooth). Sometimes, while these lights are illuminated it will shift just fine. Sometimes, when I start the truck, these lights will not be illuminated and the transmission will shift just fine. I don't know what the problem is and I don't know why there are inconsistencies in the indications. Any ideas? Thank you for your attention and any suggestions, in advance.

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[cwillard59]

I forgot to mention that the hard shifting takes place while driving, not sitting, shifting through gears. Thanks.

 

[drmorbius]

I forgot to mention that the hard shifting takes place while driving, not sitting, shifting through gears. Thanks.

The first thing to do is pull the codes. If you are getting lights there will be a code for what's causing this. Many auto parts stores will read this for you free.

 

[03_4x4Runner]

Have you ever changed the fluid?

 

[cwillard59]

Have you ever changed the fluid?

No, I just picked her up in November of '07 and all the fluids look very fresh. Maybe I should flush the tranny just to be certain?

Thanks, for the reply, 03_4X4Runner.

 

[CJ3Flyr]

I suspect it's losing a speed signal from a sensor.
:cheers: