i had my truck in park with the motor running and i noticed the went to a higher rpm like 800+ or so then the overdrive light started to blink for about 20 sec then it went back to normal rpms but i was wondering if this is common or if there is a major problem thanks

 

Means there is an issue with the transmission... Blinking OD light means a code has been stored. I would retrieve that code before doing anything else...

 

well it only does it when its wet outside and its a new tranny ill take it back to the shop its the first time it did it im gonna see if it does it again first time it did it

 

check the VSS. i believe if that gets wet it will cause the o/d light to blink.

 

Is the speedo working, cause my 99 was doing that & my speedo wasn't working.

 

chech the plugs on the transmission too.

 

vss? and the speedotmer is working fine it hasnt happend again but ill check the wiring i hate how water can ruin something

 

Vehicle Speed Sensor. it's on top of the rear diff. just because the speedo is working doesn't mean all is good. pull the sensor and clean the plugs. put a big glob of dielectric grease in the plug and put it back together.