QuestionQUESTION: i have a 90 gmc trcu k with a 700r4 transmission and it shifts into all gears but is reving out 1st 2an and 3rd i thinks its the modulator valve but i dont know where it is where is it
ANSWER: Brian,
If I'm not mistaken, the modulator is located on the driver's side of the transmission near the tailshaft. It should have a vacuum line running to it, so it should be easy to spot. It is a pretty straight-foreward swap, but before you change it out, check your lines to be sure it is getting vacuum.
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QUESTION: OK I FOUND IT BUT IT IS NOT A VACUUM ITS ELECTRONIC AND AND I CHANGED IT BUT IT IS STILL DOIN THE SAME THING (I DID DRIVE TO WORK WITH THIS CONDITION OF IT OVER REVING 1ST 2ND AND 3RD WHEN IT WAS REAL HARD TO GET IT TO SHIFT OUT OF 1ST I PARKED IT) BUT NOW IT WONT SHIFT OUT OF 1ST WITH THE NEW MODULATOR. WHAT COULD BE THE PROBLEM AND I AM ALSO CHANGING THE FLUID AND FILTER CAUSE IT SMELLED ALITTLE BURN AND DARK AND SOMEONE TOLD ME THAT MIGHT HELP
AnswerBrian,
On the modulator, there should be adjustment, or clocking, marks. you can loosen the modulator and turn it to a different position to adjust it, then road test it. Without looking at it and hearing it shift, it is tough for me to tell you where exactly to put it. Also, check the voltage going to the modulator and be sure there is power there, as it could be a bad wire or fuse. If your fluid is dark and smelling burned, it might be a band or clutch issue inside the tranny that can only be fixed by getting into it and rebuilding it. If there was a lot of metal in the fluid or the pan, that may be your issue.
