Question about 1994 Chevrolet C/K 2500

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1994 chevy 4x 3/4 ton does not engage the the front differential

I had a bad front differential shift plunger (electrical and has been upgraded) I had a new transfer case installed at aamco transmission and they fixed the transfer case but the front shift was bad and they did not fix that and told me to get a new one and I did and even tested on another vehicle and works fine. When I shift to four wheel drive it does not engage but it stays in two wheel on the front differential. My shift console does not light anymore. They also put a new wire harness on tranny and transfer case. I know it is an electrical problem and is there a good place to get a good wiring diagram so I can trace the wiring. I really don't want to deal with aamco, they are a shotty place in everett WA. Is there a seperate fuse besides the one under the dash?

Thank You, Martin WilkinsonI am having the same problem with my 1994 2500 chevy truck. In the past I have changed the actuator and this has solved the problem. One time I found a wire from the floor shifter under the truck was broken, repairing this at that time took care of the problem. This time after replacing the actuator I am having no sucess repairing my truck. If there is anythig else I can try please let me know. Thanks...

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You say you have upgraded the front actuator i assume you installed the one that comes with harness?
here is a diagram1994 chevy 4x 3/4 ton does not engage the the fron - 721ef47.gif

Posted on Jan 15, 2009

  • TripleTauto
    TripleTauto Jan 15, 2009

    BE SURE to check the ground

    Also your switch on top of transfer case could be faulty this is what the new wire in the harness goes too. It has been a long time since i wired one but i think it was a brown wire? this kit would also read off of that to locck front diff quicker.

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1 Answer

4 wheel drive indicator light is on but the front wheels are not engaging


Are they vacum operated or you have to lock it in by hand? If you have an electric over vacuum control switch on the transfer case and 2 electric over vacuum switches, they are on the passenger side front fender well near the rear by the hood hinge, they are either green or blue and made of plastic, they both have vacuum lines and 2 wires connected to them. From there the vacuum lines run down near the front differential where they connect to a slave cylinder. the vacuum routes one way, the slave plunger moves and the differential engages 4WD, the vacuum routes the other way, the slave plunger moves again and the differential disengages 2WD (similar to a 90's model dodge 4x4).

Run this easy test. Label the vacuum lines that come from the top of the vacuum switches on the fender well (front, rear) use masking tape.

Start your truck. (make sure one of those switches has vacuum, put your finger over the nipples where you unplugged the lines, if you feel suction, you got vacuum) trade the vacuum lines, front to rear and rear to front. shift into 4x4, you wont get a 4x4 light, but if you now have 4WD then the problem is in the circuit somewhere between those 2 switches and the master switch on the T-case.


Keep us udated (remember to rate this).

Dec 01, 2010 | 1991 Isuzu Trooper

1 Answer

Whenever I shift my 1988 K-3500 in to 4hi or 4low the fuse blows and will not engage into 4 wheeldrive. Any ideas on this?


On the full size, the front actuator is electric, not vacuum.

When in 4wd mode, a switch on top of the transfer case conducts 12 volts out to the actuator. Wire #50 (brown) is the 12v feed, and it conducts to the light blue wire (#900) to the actuator.
When shifted out of 4wd, the switch opens up and no voltage goes to the actuator.

Check voltage at the connector for the front actuator (at the front differential - it looks like a large bullet that threads into the front diff.) If it has 12 volts, the actuator is the problem. If it does not have 12 volts, check the transfer case switch and the power feed to the transfer case.

I'll assume it is the actuator, if the plug to the actuator is getting 12 volts when in 4wd.
The way this actuator works, is it is a sealed chamber that gets heated by voltage. When it heats, the pin in the end swells and pushes a shift fork in the front differential. The shift fork engages a spline on the passenger side of the differential, and boom! you have 4WD.

GM offered an upgrade to this actuator that is a motor instead of a heated device. However, it requires a small harness addition, a spacer, and a new actuator. It is about a $150 to $200 option.

Good luck. The actuator is usually the problem 90% of time but recheck all of the wire harness just to maker sure there is no short before replacing any parts. The actuator may not be fully engaged or disengaged and the fork to the spline may be what is causing the grinding.

88-UP C/K ACTUATOR UPGRADE
VEHICLE SERVICED: 1994 CHEVROLET FULL SIZE
PURPOSE: IMPROVE AXLE CONNECT ENGAGEMENT TIME AND
COMPONENT RELIABILITY.

SYMPTOMS: NO FRONT DRIVE AXLE ENGAGEMENT WHEN SHIFTED INTO 4X4.

Obtain the following GM part numbers:
(1) 26060073 Actuator
(1) 88959465 Harness/Spacer Kit

Jan 25, 2010 | 1989 Chevrolet S-10 Blazer

2 Answers

The 4x4 do not engage on my 1990 chevy pick up what do i need to check first


On the full size, the front actuator is electric, not vacuum.

When in 4wd mode, a switch on top of the transfer case conducts 12 volts out to the actuator. Wire #50 (brown) is the 12v feed, and it conducts to the light blue wire (#900) to the actuator.
When shifted out of 4wd, the switch opens up and no voltage goes to the actuator.

Check voltage at the connector for the front actuator (at the front differential - it looks like a large bullet that threads into the front diff.) If it has 12 volts, the actuator is the problem. If it does not have 12 volts, check the transfer case switch and the power feed to the transfer case.

I'll assume it is the actuator, if the plug to the actuator is getting 12 volts when in 4wd.
The way this actuator works, is it is a sealed chamber that gets heated by voltage. When it heats, the pin in the end swells and pushes a shift fork in the front differential. The shift fork engages a spline on the passenger side of the differential, and boom! you have 4WD.

GM offered an upgrade to this actuator that is a motor instead of a heated device. However, it requires a small harness addition, a spacer, and a new actuator. It is about a $150 to $200 option.

Good luck. The actuator is usually the problem 90% of time but recheck all of the wire harness just to maker sure there is no short before replacing any parts. The actuator may not be fully engaged or disengaged and the fork to the spline may be what is causing the grinding.

88-UP C/K ACTUATOR UPGRADE
VEHICLE SERVICED: 1994 CHEVROLET FULL SIZE
PURPOSE: IMPROVE AXLE CONNECT ENGAGEMENT TIME AND
COMPONENT RELIABILITY.

SYMPTOMS: NO FRONT DRIVE AXLE ENGAGEMENT WHEN SHIFTED INTO 4X4.

Obtain the following GM part numbers:
(1) 26060073 Actuator
(1) 88959465 Harness/Spacer Kit

Jan 20, 2010 | 1992 Chevrolet K1500

2 Answers

I have a 2002 Chevy Tahoe making a grinding noise in the front drivers side wheel, what could this possibly be?


If 4wd Tahoe, it is the CV joint going out or is out, replace part about 250 bucks, very common in 4wd Tahoe

Jan 11, 2010 | 2000 Chevrolet Tahoe

2 Answers

Four wheel drive will not engage when truck is warmed up.sometimes it will engage usually when truck is cold????


On the full size, the front actuator is electric, not vacuum.

When in 4wd mode, a switch on top of the transfer case conducts 12 volts out to the actuator. Wire #50 (brown) is the 12v feed, and it conducts to the light blue wire (#900) to the actuator.
When shifted out of 4wd, the switch opens up and no voltage goes to the actuator.

Check voltage at the connector for the front actuator (at the front differential - it looks like a large bullet that threads into the front diff.) If it has 12 volts, the actuator is the problem. If it does not have 12 volts, check the transfer case switch and the power feed to the transfer case.

I'll assume it is the actuator, if the plug to the actuator is getting 12 volts when in 4wd.
The way this actuator works, is it is a sealed chamber that gets heated by voltage. When it heats, the pin in the end swells and pushes a shift fork in the front differential. The shift fork engages a spline on the passenger side of the differential, and boom! you have 4WD.

GM offered an upgrade to this actuator that is a motor instead of a heated device. However, it requires a small harness addition, a spacer, and a new actuator. It is about a $150 to $200 option.

Good luck. The actuator is usually the problem 90% of time but recheck all of the wire harness just to maker sure there is no short before replacing any parts.

88-UP C/K ACTUATOR UPGRADE
VEHICLE SERVICED: 1994 CHEVROLET FULL SIZE
PURPOSE: IMPROVE AXLE CONNECT ENGAGEMENT TIME AND
COMPONENT RELIABILITY.

SYMPTOMS: NO FRONT DRIVE AXLE ENGAGEMENT WHEN SHIFTED
INTO 4X4.

Obtain the following GM part numbers:
(1) 26060073 Actuator
(1) 88959465 Harness/Spacer Kit

Jan 10, 2010 | 1999 Chevrolet K1500

1 Answer

1991 K2500 pickup, 350tbi,4l80 trans, 4wd not working, I have gotten it to turn on a couple of times but it never stays working. The transfer case does lock in when its put into 4wd. also the actuator is...


On the full size, the front actuator is electric, not vacuum.

When in 4wd mode, a switch on top of the transfer case conducts 12 volts out to the actuator. Wire #50 (brown) is the 12v feed, and it conducts to the light blue wire (#900) to the actuator.
When shifted out of 4wd, the switch opens up and no voltage goes to the actuator.

Check voltage at the connector for the front actuator (at the front differential - it looks like a large bullet that threads into the front diff.) If it has 12 volts, the actuator is the problem. If it does not have 12 volts, check the transfer case switch and the power feed to the transfer case.

I'll assume it is the actuator, if the plug to the actuator is getting 12 volts when in 4wd.
The way this actuator works, is it is a sealed chamber that gets heated by voltage. When it heats, the pin in the end swells and pushes a shift fork in the front differential. The shift fork engages a spline on the passenger side of the differential, and boom! you have 4WD.

GM offered an upgrade to this actuator that is a motor instead of a heated device. However, it requires a small harness addition, a spacer, and a new actuator. It is about a $150 to $200 option.

Good luck. The actuator is usually the problem 90% of time but recheck all of the wire harness just to maker sure there is no short before replacing any parts.

88-UP C/K ACTUATOR UPGRADE
VEHICLE SERVICED: 1994 CHEVROLET FULL SIZE
PURPOSE: IMPROVE AXLE CONNECT ENGAGEMENT TIME AND
COMPONENT RELIABILITY.

SYMPTOMS: NO FRONT DRIVE AXLE ENGAGEMENT WHEN SHIFTED
INTO 4X4.

Obtain the following GM part numbers:
(1) 26060073 Actuator
(1) 88959465 Harness/Spacer Kit

Jan 10, 2010 | 1991 Chevrolet K2500

1 Answer

4x4 locks in ok but when locked in it real loads also shimmy and ginds just some times on the front end


On the full size, the front actuator is electric, not vacuum.

When in 4wd mode, a switch on top of the transfer case conducts 12 volts out to the actuator. Wire #50 (brown) is the 12v feed, and it conducts to the light blue wire (#900) to the actuator.
When shifted out of 4wd, the switch opens up and no voltage goes to the actuator.

Check voltage at the connector for the front actuator (at the front differential - it looks like a large bullet that threads into the front diff.) If it has 12 volts, the actuator is the problem. If it does not have 12 volts, check the transfer case switch and the power feed to the transfer case.

I'll assume it is the actuator, if the plug to the actuator is getting 12 volts when in 4wd.
The way this actuator works, is it is a sealed chamber that gets heated by voltage. When it heats, the pin in the end swells and pushes a shift fork in the front differential. The shift fork engages a spline on the passenger side of the differential, and boom! you have 4WD.

GM offered an upgrade to this actuator that is a motor instead of a heated device. However, it requires a small harness addition, a spacer, and a new actuator. It is about a $150 to $200 option.

Good luck. The actuator is usually the problem 90% of time but recheck all of the wire harness just to maker sure there is no short before replacing any parts.

88-UP C/K ACTUATOR UPGRADE
VEHICLE SERVICED: 1994 CHEVROLET FULL SIZE
PURPOSE: IMPROVE AXLE CONNECT ENGAGEMENT TIME AND
COMPONENT RELIABILITY.

SYMPTOMS: NO FRONT DRIVE AXLE ENGAGEMENT WHEN SHIFTED
INTO 4X4.

Obtain the following GM part numbers:
(1) 26060073 Actuator
(1) 88959465 Harness/Spacer Kit

Jan 09, 2010 | Chevrolet Silverado 1500 Cars & Trucks

1 Answer

1994 gm sonoma will not engage in 4x4 mode


Well this could be numerous things..

Does the vehicle make any kind of noise when you try to shift it into 4x4? Do the dash lights on the push button shifter light up?

It is very common for the transfer case shift motor to go bad on these. They are located on the side of the transfer case by 3 or 4 10mm bolts. Another possibility would be the plunger on the front differential is bad. This is located on your front carrier assembly. It screws right into the side of the housing.

If you aren't sure I would take it to a good shop and mention these 2 things and they will take care of you.

Good Luck!

Dec 21, 2009 | 1994 GMC Sonoma

2 Answers

4 wheel drive won't engage...how do I check it?


Hi Buganbird22

I pretty much have the same problem. The odds are that it isnt the transfer case at all.

That model year has an electric over vacuum control switch on the transfer case and 2 electric over vacuum switches on the passenger side front fender well near the rear by the hood hinge, they are either green or blue and made of plastic, they both have vacuum lines and 2 wires connected to them.

From there the vacuum lines run down near the front differential where they connect to a slave cylinder. the vacuum routes one way, the slave plunger moves and the differential engages 4WD, the vacuum routes the other way, the slave plunger moves again and the differential disengages 2WD (similar to a 90's model dodge 4x4).

Run this easy test. Label the vacuum lines that come from the top of the vacuum switches on the fender well (front, rear) use masking tape.

Start your truck. (make sure one of those switches has vacuum, put your finger over the nipples where you unplugged the lines, if you feel suction, you got vacuum) trade the vacuum lines, front to rear and rear to front. shift into 4x4, you wont get a 4x4 light, but if you now have 4WD then the problem is in the circuit somewhere between those 2 switches and the master switch on the T-case.

I'll post more as I go. I've been switching mine that way for a week now, because i'm too lazy to fix it in 2 feet of snow.


Dec 13, 2009 | 1991 Toyota 4Runner

4 Answers

I drove my 1994 z71 truck through a creek and now 4x4 doesn't wrk


On the full size, the front actuator is electric, not vacuum.

When in 4wd mode, a switch on top of the transfer case conducts 12 volts out to the actuator. Wire #50 (brown) is the 12v feed, and it conducts to the light blue wire (#900) to the actuator.
When shifted out of 4wd, the switch opens up and no voltage goes to the actuator.

Check voltage at the connector for the front actuator (at the front differential - it looks like a large bullet that threads into the front diff.) If it has 12 volts, the actuator is the problem. If it does not have 12 volts, check the transfer case switch and the power feed to the transfer case.

I'll assume it is the actuator, if the plug to the actuator is getting 12 volts when in 4wd.
The way this actuator works, is it is a sealed chamber that gets heated by voltage. When it heats, the pin in the end swells and pushes a shift fork in the front differential. The shift fork engages a spline on the passenger side of the differential, and boom! you have 4WD.

GM offered an upgrade to this actuator that is a motor instead of a heated device. However, it requires a small harness addition, a spacer, and a new actuator. It is about a $150 to $200 option.

If I were you, I would buy a new heated actuator. They are available at most auto parts stores, and are about $90. They are also on eBay for about $55 plus shipping. These are very easy to change - just thread out the old one, and thread in a new one.

Good luck, That actuator is usually the problem 90% of time.

Dec 02, 2009 | 1994 Chevrolet K2500

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