Question about 2000 GMC Jimmy

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2001 GMC 2500 4WD problem

The front end does not lock in at all times when in 4 hi or 4 lo. I have replaced the acutator on the front differential and checked the solenoids on the transfer case and they appear to be operating.

In 4lo, when the front end has locked in in forward, it does not stay lock in when shifted to reverse. Why?

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  • Anonymous Dec 20, 2008

    My 200 GMC Jimmy will not shift out of 2WD and only flashes when trying to shift into 4WD-High, Auto or 4WD high...

  • driver37 Dec 21, 2008

    only will go into 4 wd sometimes like when i first start it up. after it warms up it pops out and my 4wd light flashes. colud it be low on some kind of fluid? help i cant figure it out



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  • 3 Answers

Check all lines some have vacum or small elc. motor on front gears

Posted on Dec 15, 2008


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1 Answer

4 high won't engage but 4 lo and 2wd work fine

Check for power to the front differential actuator. This actuator slides a gear in position to lock the differential to drive the front wheels. If you have power and ground to the actuator when in the 4HI position, the actuator has gone bad.The 4LO is only engaging at the transfer case, but the front wheels are still not engaged if it is not working in 4HI.

Feb 25, 2015 | 2003 GMC Sonoma Extended Cab

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2004 Tahoe 4x4 will not go into 4 hi or lo. Changed switch on dash and actuator on transfer case.

There is an actuator located in the front differential " About 15 minutes to change " . By transfercase actuator , do you mean the Encoder Motor " transfercase shift motor ? 9 times out of 10 it is either the front differential actuator or the transfer case encoder motor

Feb 15, 2015 | 2004 Chevrolet Tahoe

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Why every time when I turn the steering wheel the rear differential starts to lock and it shakes?

Do you have the vehicle in 4 wheel drive? 4 wheel drive is only meant for slippery conditions. It will act exactly as you describe if on dry surfaces.

Aug 22, 2014 | 2002 GMC Yukon Denali

1 Answer

My 2002 gmc yukon slt wont switch out of auto fwd? It was working fine in 2 hi then i switched it to 4 lo the light on the 4 lo started blinking while it was still blinking i accidentally hit the auto...

You need to replace the lockup servo mounted in the front differential housing. the light will blink to indicate that the lockup servo is not engaging/disengaging. you can get the servo at a local parts place. It is very easy to replace and is easily accessible.

Mar 23, 2011 | 2003 GMC Yukon

1 Answer

I have a knocking noise in my front end whenever I put my 1998 gmc sierra z71 in 4 wheel drive

when was the last time you've checked the fluid level in the front differential?
Try this, quickly. these gears don't last long when the fluid level is low, and it's a real big job to replace the gears/differential housing.

I hope this helps, ask if you need anything.

Jan 10, 2011 | 1998 GMC Sierra

1 Answer

I removed the 4wd actuator on my 1997 1500 gmc located on the front differential and pressed the 4wd hi button in the cab. The actuator traveled out. I then pushed the device inside the differential...

4wd actuators are in the transfer case not the diff housing
on a diff housing it is more likely to be a diff lock to lock the 2 front wheels together

Jul 02, 2017 | GMC Sierra 1500 Cars & Trucks

1 Answer

I would like to upgrade from the present vaccuum 4wd actuator to electric solenoid set up for my 2001 s10 blazer. Who sells this?

There is no electric solenoid set up for the S10's, the upgrade was for the full size SUV's from the early 88 to 98 that had a thermal actuator. There is a mechanical system that is made for the S10's but it requires drilling a hole through your fire wall, running a cable into your cab and mounting the cable lock somewhere under your dash for easy access to lock in your differential.
I had the same problem and i just locked up my front differential all the time, it's been like that now for over 10 years without any issues. The transfer case is not locked up so your front axle is still not synced with your rear axle and is still free to rotate at a different speed then the rear. Just make sure you service the front differential like your suppose to and you should be fine on running with the front differential locked.
Thank you for using fixya and check to make sure that there is no cracks i your vacuum line that is keeping your front actuator from functioning or a failed vacuum switch on top of the transfer case.

May 13, 2010 | 2001 GMC Sierra Crew Cab

1 Answer

Had 2001 GMC Sierra in 4WD Auto and went to put in 4 hi. then Service 4WD light came on and selector wouldn't let me select anything and the truck stayed in 2 hi.

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.

Jan 07, 2010 | 2001 GMC Sierra Crew Cab

3 Answers

97 GMC Z71 4X4 Not Locking in

If it's a shift - on - the - fly 4wd, then call your local Chevy truck dealer. There was a recall on the Electronic 4wd on these trucks. (common problem). Try this just for the heck of it. With the truck stopped, put in 4hi/lo, then put it in reverse. Back up slightly, (about 5ft or so) and then put it in drive (or first in a manual trans) and go forward. Did it lock in? If it locks in but won't unlock, try backing up to unlock. Hope this helps.

Jul 26, 2009 | 1999 Chevrolet Silverado 1500

1 Answer

My 2001 GMC Jimmy is stuck in 4 Lo.

i believe those are vacuum controlled on top of the transfer case is a plug with 3-4 vacuum lines going to it,you will need to take it out and see if the check ball is stuck if it is it needs to be replaced

Nov 12, 2008 | 2001 GMC Jimmy

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