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1998 Blazer 4 Wheel drive

03-26-2003, 10:54 AM
Can anyone help me? I have a 1998 Chevy Blazer and the 4 Wheel drive won't work the dealer said that I need a 4 Wheel drive modual and want's to charge me 600.00 to replace it. I can buy it for cheeper but I can't find out where it is located at.

03-26-2003, 01:43 PM
Based on the price you said I would guess you are talking about the Encoder Motor.

Here is a blowup of the transfer case the encoder callout number is highlighted in teal.

07-05-2003, 08:21 PM
Ive got a 1998 chezy blazer with the automatic 4 weel drive button. Its been jammed for a month now. The mechanic said it would be $1200 to fix it!! But said it wasn't a emergency job. It seems like a ton of cash to fix this, could it just be the wire is shorted out?? Help Please

07-07-2003, 01:57 PM
hey man, I have a 95 blazer with the same problem with my 4x4. I looked into it and found that inside the buttons on the dash are little light bulbs. check to see if those bulbs are good. it turned out that I had a bad bulb. The dealer its gonna charge me like 4 dollars for a new bulb. Look into that.

08-17-2003, 08:24 PM
My Blazer wasn't shifting in and out of 4 wheel drive and I was told I needed a new transfer case actuater, some call it a Encoder Motor and what i found was when they removed the + battery terminal and rubed it against metal to ground it, when they hooked it back up & the 4 wheel drive worked again, what this did was re-boot the computer in the blazer and all is well again

08-17-2003, 08:36 PM
Try disconnecting your battery and hooking it back up after 10 seconds and see what happens. Sometimes the 4WD module gets logic lock up and this would reset the system. Its worth a try!!

08-19-2005, 10:13 PM
My father replaced all the components that he can find to try to fix this problem. Logic Lock did not fix the problem, and he replaced the encoder motor, the 3 button switch in dash, and the metal box behind the dash and it still did not fix the problem.

Is there any other component that could cause the problem or that needs to be replaced.

The problem is that it only goes into 4wheel low not 4 wheel high.. and acts funny has trouble switching form 2high to 4wheel low and takes a couple tries.

Any help will be appreciated.


08-20-2005, 01:38 AM
I had *major* problems with the 4x4 on my 95 Blazer and was able to fix it in the following way:

Before you replace any motors or even check any wiring look at the most simple thing... the fluid inside the transfer case.

This takes 3 minutes for the mechanically inclined, 10 for the not as inclined. Jack your truck up on jack stands or do like I do and use my ramps.

The transfer case has two plugs on it, a lower "drain" plug and a higher "level check / fill" plug. Take out the upper (level check) bolt plug and see if any fluid comes out.

The fluid should be at the level check plug and no lower than 1 inch below it.


There is a calibration technique. On flat ground switch your vehicle in to neutral. Press the 4hi button, wait until it shifts and stops flashing, then switch gears in to park. Switch back in to neutral, press the 2hi button and wait til it shifts, and shift back to park.

And I assume you checked your fuses before you came posting on here? :P

08-20-2005, 12:56 PM
just one other thing to note... make sure the vaccuum line is intact/connected/unobstructed (see #51)

02-18-2006, 05:05 AM
Well weíve got the same problem over here in Switzerland on this big Snowing day of Feb. 18.2006
I've a Blazer from 1999-2000 imported to Europe with the same 4x4 Bugs they have when they leave the factory in the US.
My best tip for today is:
Disconnect the battery for at least 15 minutes (removing the red cable will be enough and the sparks are not dangerous as long you donít touch another metallic car piece with your key). (Need an 8 Key)
Use this time to enjoy the snow hiding your nice and beautiful Chevy!
Maybe, take a look under the hood to be sure all pneumatics wires are connected well and are not broken or in a bad shape.
If there are broken take some adhesive and patch them with all your best efforts.
Cleaning before patching could be a solution for a longer time!
Some silicon spray could be useful for those kinds of gum wires especially in the Siberian winter of Switzerland or in Alaska.
Be certain no damage is visible under the hood, firmly reconnect the red battery cable ensuring it is dry and clean.
Sit and try starting on neutral (Itís a tradition in Switzerland!) and engage 4WD-Low. Wait at least for 5 to 10 seconds before changing to another mode.
If itís works, nothing is broken in your good old Chevy.
Total costs: dirty and cold hands!
I send you best regards from Montana Ė Switzerland!

02-18-2006, 06:44 AM
1st Check vac actuator under battery tray for tears, or leaks, and that the vac hose is connected. Replace if found

2nd Check vac hose leading from vac actuator to vac switch on transfer case for cracks and dry rot. Replace if found.

3rd Check remaining 2 hoses from vac switch on transfer case for dryrot or cracks Replace if found.

If all of the above are fine, disconnect your negative battery cable for 1/2 hour then reconnect it. If your 4x4 works after that you probably have a failing TCCM (Transfer case control module)

If that doesn't solve it, it's most likely the encoder motor

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