Question about 2003 GMC Envoy Xl

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What's the difference between A4WD and 4WD Hi in the snow? Which should I use in the snow?

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A4wd means it senses wheel slipping automatically and engages 4 wheel drive as needed, use that.

Posted on Dec 29, 2010

Testimonial: "Thanks for your response. I'll use A4WD then."


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1 Answer

Service 4WD has come on twice, two winters in a row.

Its your control module for the 4 WD on the transfer case hanging. They go bad often. I would replace

Jan 11, 2015 | 2003 Chevrolet TrailBlazer

1 Answer

Expedition is AWD but drives all of the sudden like it's stuck in 4WL ????

There is a small difference in what you are saying here. "AWD" stands for All Wheel Drive. 1999 Ford Expedition is equipped with (A4WD) which stands for Automatic 4-Wheel Drive. There is a big difference between these two systems. The AWD has no driver controls and drives all of the wheels all of the time. the A4WD system ia capable of shifting in and out of 4WD automatically as needed, depending on wheel speed sensor data that indicates wheel slippage. The A4WD also has a 4WD Mode switch mounted on the instruent panel to allow the driver to override how the system operates.

FIRST, check to make sure that the 4WD Mode switch is in the "AUTO" position. If the switch is in the correct position, then you will need to scan your transmission and transfer case control modules and perform visual an functional inspection of the system to pinpoint the cause of the malfunction. It could be anything as simple as a defective mode switch to a major problem like bent/broken shifting forks inside the transfer case, requiring complete overhaul. Proper diagnosis will be required.

Mar 24, 2012 | 1999 Ford Expedition

1 Answer

What does A4WD mean?

It stands for automatic 4 wheel drive, the WD drive will engage when the vehicle senses tire slippage. Good to use when driving on somwhat snow covered roads where some driving might be on on the pavement , some on snow. Not good to use the 4wd when on pavement especillay when turning. OK.

Feb 06, 2012 | 2002 Ford F150 Regular Cab

1 Answer

The service 4wd light came on in my 2002 envoy.

There are two motors under the vehicle. The front axle actuator moves ONLY during 2HI->A4WD and A4WD->2HI transitions. The transfer case encoder motor makes a lower pitched noise in every mode transition: 2HI->A4WD, A4WD->4HI, and 4HI->4LO, and the three transitions upwards.

If EITHER of the motors fails to do what the TCCM commands it to do, the switch light will flash and the Service 4WD light on the dash will come on.

If you're a DIY mechanic, you might look into them further, or just take it to a mechanic who knows our systems. The average mechanic is not going to know the theory of operation of the trailblazer/envoy 4x4 system, which is pretty unique in the industry

Mar 11, 2011 | GMC Envoy Cars & Trucks

2 Answers

Should I drive in a4wd or 2h 2003 expedition

4WD is for soft ground or snow Do not use 4WD on dry pavemant for it wears out the transfer case 4 wheel drive gearing faster and the front tires out very quickly too

Apr 17, 2010 | 2003 Ford Expedition

4 Answers

Do I drive in A4WD or 2Hi?

Either one is fine I would use 2wd unless it is raining or snowy or you are on loose gravel. But you can leave it in a4wd all the time. In a4wd it will stay in 2 wd until the vehicle sees wheel slip, then it will shift into 4wd automaticly. If you have it in 2wd it won't shift into 4wd by itself.

Mar 27, 2010 | 2003 Ford Expedition

1 Answer

While set in A4WD the indicator will start

ask another GM dealer, have them check for related TSB's. could be the front acuator.

Jan 02, 2010 | 2005 Chevrolet TrailBlazer

1 Answer

4wd hi is not working, the a4wd works. the 4hi sounds like it is kicking in but the back tires spin

it is normal if u get tire spin in 4wheel or in all[a4wd]-- even auto[4wd] uses the rear spin to engage the front differential

Dec 22, 2009 | 2004 GMC Envoy

1 Answer

Service 4wd light

what causes the 4wd to kick in when you have it in 2wd

Mar 13, 2009 | 2004 GMC Yukon

2 Answers

Difference betweeb 2wH part time 4wd and 2wH + full time 4wd

The difference between 4WD Full-Time and 4WD Part-Time is not exactly what one would guess simply from the names without knowing. The main difference is basically an added differential in the transfer case vs. the front and read driveshaft being locked together.

Here's what that means to you.

4WD Full-Time (open differential in transfer case)- Is great for snow and ice. It is safe to leave locked into this mode anytime, even on dry pavement or highway.

4WD Part-Time - This is the traditional type of 4WD that you have in vehicles. It will give you added traction offroad, it's good for mud, rock climbing, snow... It is actually not as good on ice as 4WD Full-Time. Do not drive on dry pavement, especially around corners, in this mode. It can cause major damage, and at the least will cause unnecessary wear to the components.

I hope this helps.

Jan 11, 2009 | 1996 Jeep Cherokee Country

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