Need to know what the factory speaker sizes for my 1990 gmc k1500

no they are not

My personal suggestion would be to go for these repair catalogs from
www.reliable-store.com instead. much better info on all vehicles, complete details, and they also have live assistance feature

Ebay and www.crutchfield.com have indexes of all the common cars and the size of the factory speakers which fit them.

you need to replace the front actuator on differential it was a common problem for these to go out

check actuator at transfer case may be moving but not actually engaging the 4x4 may need adjustment or service

Here ya go. enjoy!
2002 GMC Sierra C1500 Car Radio Wire Color Codes
Car Radio Battery Constant 12v+ Wire: Orange
Car Radio Accessory Switched 12v+ Wire: Yellow
Car Radio Ground Wire: Black/White
Car Radio Illumination Wire: Brown
Car Stereo Dimmer Wire: Gray
Car Stereo Antenna Trigger Wire: N/A
Car Stereo Amp Trigger Wire: N/A
Car Stereo Amplifier Location: Under the center console.
Car Audio Front Speakers Size: N/A
Car Audio Front Speakers Location: N/A
Left Front Speaker Positive Wire (+): Tan
Left Front Speaker Negative Wire (-): Gray
Right Front Speaker Positive Wire (+): Light Green
Right Front Speaker Negative Wire (-): Dark Green
Car Audio Rear Speakers Size: N/A
Car Audio Rear Speakers Location: N/A
Left Rear Speaker Positive Wire (+): Brown
Left Rear Speaker Negative Wire (-): Yellow
Right Rear Speaker Positive Wire (+): Dark Blue
Right Rear Speaker Negative Wire (-): Light Blue

The size of speaker that will go into that vehicle is a 6 1/2". You will need to take off the door panel in order to remove speakers. Once door panel is removed, locate screws holding speakers and remove and reinstall new speakers.

PLEASE RATE MY SOLUTION, THANKS.


1996 GMC Truck Factory
Stereo Wiring Chart
Car Radio Battery Constant 12v+ Wire: Orange
Car Radio Accessory Switched 12v+ Wire: Yellow
Car Radio Ground Wire: Black
Car Radio Illumination Wire: Brown
Car Stereo Dimmer Wire: Gray
Car Stereo Antenna Trigger Wire: N/A
Car Stereo Amp Trigger Wire: N/A
Car Stereo Amplifier Location: N/A
Car Audio Front Speakers Size: N/A
Car Audio Front Speakers Location: N/A
Left Front Speaker Positive Wire (+): Tan
Left Front Speaker Negative Wire (-): Gray
Right Front Speaker Positive Wire (+): Light Green
Right Front Speaker Negative Wire (-): Dark Green
Car Audio Rear Speakers Size: N/A
Car Audio Rear Speakers Location: N/A
Left Rear Speaker Positive Wire (+): Brown
Left Rear Speaker Negative Wire (-): Yellow
Right Rear Speaker Positive Wire (+): Dark Blue
Right Rear Speaker Negative Wire (-): Light Blue

Those are 5 Inch Speakers and Tweeters I do Believe.

1990 Mazda 626 Car Stereo Wiring Diagram
Car Radio Battery Constant 12v+ Wire: Blue/Red
Car Radio Accessory Switched 12v+ Wire: Blue/White
Car Radio Ground Wire: N/A
Car Radio Illumination Wire: Red/Black
Car Stereo Dimmer Wire: N/A
Car Stereo Antenna Trigger Wire: N/A
Car Stereo Amp Trigger Wire: N/A
Car Stereo Amplifier Location: N/A
Car Audio Front Speakers Size: 4′
Car Audio Front Speakers Location: Dash
Left Front Speaker Positive Wire (+): Blue
Left Front Speaker Negative Wire (-): Blue/White
Right Front Speaker Positive Wire (+): Blue/Red
Right Front Speaker Negative Wire (-): Blue/Yellow
Car Audio Rear Speakers Size: 6 1/2′
Car Audio Rear Speakers Location: Side Shelves
Left Rear Speaker Positive Wire (+): Blue/Red
Left Rear Speaker Negative Wire (-): Blue/Green
Right Rear Speaker Positive Wire (+): Blue/White
Right Rear Speaker Negative Wire (-): Blue/Green