Question about 1991 GMC Sierra

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How do I locate the transmission modulator valve on a 1991 GMC Sierra 1500 4.3?

Posted by Jose GARZA on


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SOURCE: Fuel filter location Sierra

I have been told by a mechanic that the fuel filter is inside the fuel tank. Have to either drop the tank or remove the pickup bed. Access is on the top of the tank. This is poor engineering.

Posted on Mar 13, 2009


Nate Stansfield

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SOURCE: Need location of valve to recharge air

Some have the valve type that looks like a tire valve. Most newer vehicles have a red and yellow cap on the adapter. Red is for the high flow and yellow is for the low pressure flow

Posted on Jul 03, 2009



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Posted on Dec 02, 2009


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SOURCE: where is the vent valve located

The vent valve for what?

Posted on Dec 13, 2009

John P Schwantes Jr

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SOURCE: 2004 gmc 1500 sierra heater control stuck on

Defrost is the default position. Is the control a autyomatic temperture control unit? ( you set the temp and select automatic) if it is the system is completely electronic. You push the buttons and the control still says defrost or can you select something else and the control shows it but it just keeps coming out the defrost? If the control changes and the air comes out the defrost anyway and the cheack engine light isn't on, then the problem can be blown fuses or an air door actoater not working. Does the dash emit a clicking sound? if it does with the covers off the bottom of the dash reach around touching the different pieces till you touch the idem that is clicking. this is an acutor motor, or blend door motor. they have gears in them that wear out and break the motors aren't repairable and you just replace the ofending motor. the door that is moves can be stuck. and may have to be freed up with blaster, WD40, or other rust buster till it moves easy. maybe after getting the door to move smoothly you can get the old motor to move the door wiithout having to install a new one.

Posted on Jan 06, 2010

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How do i replace transmission modulator valve on a 1991 gmc sierra 1500 4.3

UNLESS you have a TH400 3 speed HD automatic transmission, which I HIGHLY doubt being it's a 1500 with a 4.3, you won't have a vacuum modulator. UNLESS someone swapped an older TH350 or TH400 transmission into the truck.

Instead you'll have what called a TV cable, or throttled valve cable.

This cable should be located on the passenger side of the transmission and is routed up to the side of the throttle body and hooked up like the old "kick down" cables.

The TV cable isn't simply a "kick down" cable, even though it does act like one, it also adjusts the pressure for the transmission to shift at different throttle positions. Much like the old vacuum modulators did.

Hope this helps.

Feb 10, 2015 | GMC Cars & Trucks

1 Answer

1991 4 x4 gmc sierra 1500 rear wheel seized

if both wheels are not turning look into the diff. but if only one tire is seized check for a brake problem.

Nov 03, 2013 | 1991 GMC Sierra

1 Answer

Location modulator valve


Apr 23, 2013 | 1994 GMC Sierra

1 Answer

1991 4.3 GMC SIERRA SLX 1500 engine starts but as soon as you go to turn the steering wheel or turn the a/c on the engine dies,have any idea ? ihave changed multiple sensors.

I would check the idle air control valve and the throttle body.
The valve could be faulty or the throttle body could have dirt blocking the air passage.
If you keep the RPM above idle speed does it still stall ?

Sep 04, 2012 | 1991 GMC Sierra

1 Answer

2005 gmc sierra Z71..driving down the road

This transmission is shifted by a computer via electric solenoids that open and close hydraulic fluid pressure passages when signaled by the computer control, so any kind of a problem with the external wiring harness to the valve body or the valve body wiring harness or the PCM (powertrain control module can cause this symptom. The most common cause of your particular problem is a damaged open or shorted shift solenoid, this causes the transmission to go into two gears at once, the computer senses this and shifts the transmission to neutral to stop any damage to the transmission.

Nov 16, 2011 | 2005 GMC Sierra 1500 Hybrid

1 Answer

Does a 1991 gmc 1500 have a cabin filter?

No, it does not. I cannot find a cabin air filter listed for a '91 GMC Sierra 1500. Sorry :(

Mar 01, 2011 | 1991 GMC Sierra

1 Answer

Where is the modulator valve located on the transmission of a 1993 GMC Sierra?

Will be to the back of your transmission, on the side, will have a vacuum hose going to it.

Dec 11, 2010 | GMC Sierra Cars & Trucks

1 Answer

What size engine goes into a 1991 gmc sierra 2300

2300????? Huh. I though they were 1500, 2500. i could be wrong. ususaly in the 3/4 tonne vehciles, they have a small block V8. I hae seen quite often a 350 cubic inch...but, depending on your transmission and engine braket mounts, not to mention mechanic skills and fabrication abilities, you could put whatever you want in it...As i said, probably a 350 small block is what was in there...probably

May 30, 2010 | 1991 GMC Sierra

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