Chevrolet Repair: 1991 1500 p/u, vehicle speed sensor, throttle linkage

Question
QUESTION: My truck is an 1991 1500 p/u with 350 v-8 overdrive trans. it will not shift out of first gear the fluid is full and it looks clear and no trash in it
. Is there a part that I can replace like a modulator valve or something please help
thank you
bobby

ANSWER: Hey,

  If the trans has a detent cable attached to the throttle linkage make sure the cable is bound up or the plastic end isn't broken.  They typically cause early shifting and low line pressure if they are off but the cable adjuster could be out of adjustment.
 Does it upshift if you max out the RPM? Late and Hard?  or no upshift at all no matter what.  What is the Maximum speed you can get out of it.  Are you sure it is starting out in first and not second?



Wayne


---------- FOLLOW-UP ----------

QUESTION: does not upshift with max rpm max speed is about 40 mph

Answer
That trans should be fully electronic and if it doesn't upshift out of first it could be the Vehicle speed sensor itself or the wiring to the PCM.  You need to check and see if there is a signal to the ECM or not.  They typically rot out under the battery mounting panel.

Wayne