I have a 2001 Blazer 4x4 and I put the truck in 4 Hi the other day and now I can't get the truck to shift out of 4Hi. I have replaced the transfer case shifting motor, and the dash 4WD dash switch and it still will not shift out of 4Hi. If I push the 2Hi button the 2 Hi button will flash, but go back to 4Hi after a few seconds. If I push the AUTO WD button it will stay on, but it does not shift out of 4 wheel drive. There is also a light on the dash the indicates "4WD Service Required". HELP!

Joe

 

I took the truck to my local Chevy dealer and he told me that the transfer case is locked up and needs to be replaced. When I got into my truck the dealer had removed the encoder motor, and was inside the truck. When I drove the truck it seems to be in 2 wheel drive. Can I leave it like this and just drive it as is, or am I damaging something?

 

The transfer case is probably not locked up, I cant remember which side of the truck you jack up in the front, left or right to spin the wheel by hand to see if its in 4wd, I suppose you could do both sides, if both tires spin freely, then its not in 4wd. The reason its stuck in 4wd could be the vac switch at the transfer case.

 

Is the vacuum switch located on the transfer case or up by the firewall on the 2001 Blazer?

 

I had the exact same problem sadly. Took it to the shop, great priced mechanic I know. Turns out the transfer case was bone dry. I had just bought the blazer about a month previous. New transfer case with 80k on the clock from a salvage yard for $350, he charged $300 to install.

 

Today I bought a Dorman vacuum switch for transfer case. Put the Jimmy on a lift. Removed the rubber vacuum connection. I blew air through the 3 lines to make sure they were all open and going to the right places. I stuck a wade of paper towel in the ends so I would know if it was the right line. The middle one directly behind the little nipple goes to the vacuum acctuator under battery on mine, I did this one at a time and checked to see if my paper was blown out of lines. All lines went where they were supposed to go. I used a stubby 7/8" wrench to get the switch out. Upon the install of the switch into top of Transfer Case, I could not get it to install. I tried and tried, gave up and went home. I came back an hour later and tried again. I could not even put the old one back in the hole. What a bummer. My arms were about to fall off. The moral of this story is that the switch is not 90 degrees to the transfer case. It slants forward by about 15 degrees to the front. I even took out the front driveshaft to get better access. ( Not needed to be done) Once I realized it was not 90, I had no problem installing the Dorman or the old one. I thought I was going nuts! I guess it is because it is a GMC. Still not happy with the pull on the actuator but it does move about 1/4". Is 1/4 " enough to engage the w4d?
Regards,
David

 

My son came over the other day, and we again tried to get this truck into 2 WD. We installed an new 4 button switch on the dash, but that did nothing to resolve my problem. We removed the battery and started the truck, and that vacuum canister and cable seem to work ok. We removed the electrical switch that is located on the front Tcase at the end of that cable and that seems to be working ok as well. We re-installed the rear Tcase encoder motor that the dealer had removed, and tried the the system again. We can hear the encoder motor turning and can feel the gears moving in the housing of the encoder assembly, but now the truck seems to be stuck in neutral, and the truck will not move. We again removed the encoder motor and manually shifed the Tcase into some position. We left the front drive shaft removed, and now the truck moves ok, and the front wheels seem to rotate freely. If I leave the front driveshaft removed will I damage the Tcase or the front Tcase? The 4WD Service light is still on in the dash, but at least I can drive the truck, but no 4WD though. It seems to be down to the computer module, new encoder motor, new rear transfer case assembly, but I hate to just start replacing components without knowing what is the problem. My local salvage yard has a rear transfer case off a 87K mile truck for $250 that does not enclude the encoder motor. NAPA wants $200 for a new encoder motor, and a new control module is $400. Has anyone had any luck with used encoder motors or control modules? Hate to installed used stuff and not know if they are any good, and still have my problem. HELP

 

Your previous posting said that you thought it was in 2WD--when did it shift back into 4WD?

The dealership told you it needed a t.c., and you hate to start replacing components w/o knowing what is the problem? Do you disagree with their diagnosis? If so, get another quote. A mechanic with a trouble code reader that deciphers 4WD/AWD codes can determine the likely problem.

If you believe the t.c. is in good working condition, remove the shift motor and shift it manually at the t.c. input shaft with a wrench.

You said you already replaced the motor...why do you want to replace it again? Don't know what model you need, but the motor can likely be found for less than 200 new.

 

When the dealership removed my used Tcase control motor then indicated that they thought that it was in 2WD, but I could still feel the front wheels dragging when I turned a corner.

I know the dealership indicated that they thought that the Tcase was bad, but if that is true, why can I shift it manually. I agree with you I am going to take it to a different mechanic this week.

I previously replace the shift motor with a used motor, which I returned to the salvage yard, in that it did not change my issue. So I don't know if the used one was also faulty.

 

gotcha. I'd say #1 get the codes read. Start there. If you have been successful in shifting the t.c. manually then the t.c. is likely ok.

For me, the shift motor was the issue and a used motor did not fix when a local shop tried it. I put the new motor in and done. Good luck.