Hi my name is ***** ***** I will be happy to assist with this today.In some cases I may need more info to assist better.I apologize for any delay.
The first thing that should be done here is to have the fault codes checked with a scan tool that will plug into your vehicle and can read all computers to see what codes are set.Once this has been done any codes set can be diagnosed to help locate and repair the fault here.
Usually if this was the speed sensor at fault here your speedometer may read differently then what the vehicle is actually traveling so the speed sensor may not be the cause here.
What can cause this here is one of the shift solenoids in the transmission valve body or the transmission valve body itself acting up.The flush can sometimes free up and remove debris from the valve body and the solenoids correcting this fault here but this doesnt always work.It is worth having done though as it does sometimes work.
I would start with having the fault codes checked just to see if any codes are set.If you can do this and post the code(s) here this will help.Places like Auto Zone will usually read out these fault codes free of charge.
I would say that transmission solenoid failure as well as valve body failure are usually most common for this issue here.
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