Thank you for the donation.
Speedometer receives signals from the Vehicle Speed Senor (VSS) to operate and quite often the fails causing the problem and it could affect the transmission.
You need to check the speedometer operations and confirm it is only the sensor that is at fault.
Is the D4 light blinking when the problem occurs?
Did you try to retrieve for trouble codes?
What is the trans model?
Monday, July 12th, 2010 AT 2:11 PM