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I was wondering if anyone could offer some advice to an issue I have been experiencing with my 1997 Chevy Blazer? The problem I am experiencing is after having engaged in 4-wheel drive “4-HI”, I can switch back to “2-HI” but, you can feel that the front differential is not fully disengaging from 4-wheel drive.
About three days ago I used the 4-hi because I was on an icy hill. As always it engaged and I made it up the icy hill with 4-wheel drive without an issue. When I switched back to “2-hi” (rear wheel drive only), the push button switch on the dash indicated that the switch back to 2-wheel drive was successful, though I could feel in the steering and hear the front differential was still engaged. Eventually after putting it into natural and engaging then disengaging the 4-wheel drive into 4-LO, the front differential will finally disengage. My Chevy Blazer is a 1997 base model with the 4.3L Vortec, 4×4 and utilizes the NP-233 – 3 button switch controlled 4-wheel drive.
I have tried many things to correct this issue. I removed the battery and the battery tray and saw that the vacuum actuator’s diaphragm was still sucked in even though the 2-wheel drive mode was enabled. When I removed the vacuum house from the actuator there was a puff of air that came out and the actuator disengaged the diaphragm almost completely. I also noticed the actuator cable that runs down to the front differential was hard to work back and forth. I tested the actuator, it tested good and held vacuum. I replaced the actuator cable and still it seemed to not move very freely when pulling it by hand. I also replaced the Transfer Case Switch that mounts on top of the Transfer case with the 3 vacuum hoses. Now the vacuum tests good going to the actuator and properly releases the diaphragm when switching into 2-wheel drive.
My theory is there is another Transfer Case 2-wire switch the mounts on the front of the front differential right next to where the actuator cable runs into the differential. This sensor is covered in oil and may not be working. Does anyone think this maybe what is causing the cable to not move smoothly and is what is causing my front diff to be staying partially engaged? Also I recently replaced two
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Welcome to the forums!
Some vehicles can not be shifted on the fly so double check your owners manual.
Now, some things to take into consideration is to make sure that all 4 tires are the exact same size and same brand. Not all tires are created equal between different brands. If you have off sizes, it may cause drive line windup.
We also have a link to free Chilton’s online that may have some trouble shooting steps for you. Its located in the “How To” section, or you can just use the search function.
Yea you might want to check the procedure for going in and out of 4WD, on some models you need to drive in reverse briefly in order to fully disengage 4WD so check your owners manual for the procedure for going in and out of 4WD.
Sigh. Same thing happened to me. I have the same transfer case and push button system…except it’s in my 1998 Astro. Was AWD, got converted to 4wd. No complaints, but this last year I put new tires on the van. Not BRAND NEW, but in really good shape. However, they are all the same brand, but one tire on the front is a 100T and the other is a 102T ( load rating ). Same tire otherwise…Kumho KR21’s.
Here’s the rub. I could shift in and out of 4wd on the fly, no problems. Only had to stop to shift into 4WD LO in park or neutral. Well, I put it in 4Hi on some ice, pulled onto the highway and could hear the transfer case whining. Didn’t do that before the tire change….hit the switch to 2WD. No dice. It moved the acutator, but the 4WD didn’t disengage until a few miles later, and then it did it with a THUD.
The second time I tried it, it make a louder THUD, and now my van has 2WD, and 2WD LO.
It’s your tires. There is enough of a rolling diameter difference to preload the transfer case/front axel to the point where it can’t “unmesh” until it gets the preload off of it. Whatever went “THUD” in my van is gonna happen to your truck until you get 4 tires of the same diameter.
Don’t lunch your transfer case out of ignorance, or reluctance. AWD and 4WD on the highway always want 4 equally rotating tires to stay happy. If they aren’t, then those Transfer cases aren’t happy and they won’t play well for very long. And a transfer case isn’t a terrible job, but it isn’t cheap either.
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