Results 1 to 4 of 4

Thread: Modulator valve on my turbo 400....

  1. #1
    Junior Member
    Join Date
    Dec 2011
    Posts
    4

    Modulator valve on my turbo 400....

    Hi everybody!

    I need some mechanical help here. I just bought a 1986 GMC Sierra 1500. It has a 4.3 Liter V6 with a turbo 400 transmission. Odd huh? The engine is out of a van I'm thinking because the oil filler cap is extended to the front of the motor.
    Anyways the transmisson is having a hard time shifting between gears. It won't shift until I'm at high RPM. I changed the filter and fluid in the transmission, also changed the modulator valve. I followed the vacuum line back to the motor where it goes into the intake manifold. It splits off from there two directions, one goes behind the motor over on the other side of the power booster to what appears to be an emissions box or something. The other heads towards the front of the motor but it has been cut off and capped with a screw. Alot of my vacuum lines and emissions have been removed. Any suggestions or thoughts would be greatly appreciated. I'm new with vacuum lines and emissions but i'm learning there importance. I want my truck to shift properly also.
    Thanks Alot!
    Gabriel

  2. #2
    Senior Moderator chevychase's Avatar
    Join Date
    Oct 2010
    Location
    truck forum .org
    Posts
    15,885
    Blog Entries
    2

  3. #3
    Senior Moderator chevychase's Avatar
    Join Date
    Oct 2010
    Location
    truck forum .org
    Posts
    15,885
    Blog Entries
    2
    Just like oldmech said in his post.. all you really need is a vacuum to distributor .. brake booster ,and modulator valve.
    Rest of it is emissions .

  4. #4
    Moderator
    Join Date
    Jul 2011
    Location
    Central Oklahoma
    Posts
    4,195
    I would try to pull that T off that line for the tranny, hook the modulator vacuum line up by its self drive it see if it shifts better, it could be its losing some its vacuum needed to work right. When you start T'ing vacuum lines you lose vacuum each time its split.
    1994 white ext cab chevy silverado 5.7 rolling 230k miles
    stock with air filter lid flipped,
    open flowing exhaust to a 40 series flowmaster dumped.
    God Bless America, Support our Troops!

Similar Threads

  1. Can you test a transmission modulator???
    By 83GMC in forum GMC Truck Forum
    Replies: 4
    Last Post: 11-15-2011, 09:09 AM
  2. Egr valve
    By gonmoises in forum Chevy Truck Forum
    Replies: 2
    Last Post: 06-24-2011, 12:00 PM
  3. PCV valve
    By matt brooks in forum Chevy Truck Forum
    Replies: 5
    Last Post: 10-05-2010, 07:51 PM
  4. IAC valve
    By duckle1 in forum Chevy Truck Forum
    Replies: 17
    Last Post: 09-29-2009, 02:08 PM
  5. ERG Valve
    By Pantharen in forum Ford Truck Forum
    Replies: 10
    Last Post: 05-13-2008, 08:07 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •