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Vacuum diapragm actuator band-aid on 96 chevy blazer four wheel drive

I inherited a rust bucket that ran great but had lots of small, irritating problems. One of those problems was the 4 wheel drive not engaging the front axle. The actuator is a big vacuum diaphragm that pulls a cable that moves a shift fork that engages the front axle to the transfer case. The problem was that the vacuum actuator was covered in very tiny pinholes. I verified this by applying a vacuum, seeing the diaphragm pull in its guts, then watching it slowly re-inflate and hiss at me with the vacuum hose still attached and no other visible or audible leaks. What I found was that, in a pinch, a couple of layers of liquid electrical tape will seal it up enough to make it work fine for a couple of weeks. The trick is to make sure to clean the rubber well with denatured alcohol and to let those layers dry COMPLETELY before applying vacuum again. Only takes a couple of hours. Helps when you live upstate in the mountains and nobody can get your part for a few days. At least you can get unstuck, drive down to the parts store and yell at the guy IN PERSON.

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My 1989 toyota 4-runner 4-wheel drive not working.


Apr 14, 2017 | 1989 Toyota Camry

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four wheel drive wont engage

If you have push button 4-Wheel Drive, it is recommended that you use it every once in a while, in order to keep gunk, rust, and corrosion to build up on moving parts. The mostly likeley (though not definite) reason would be that you let the 4-wheel drive unused for so long that corrosion has built up on the parts and the actuator that engages the 4-Wheel Drive doesn't have the power to engage it past the corrosion. You'll need to take it in to be cleaned, or to have parts replaced. In the future, every month or so, engage 4-Wheel Drive and drive around in some mud, grass, sand, or any other loose ground for a bit, just to keep the parts moving and clean.

The service Four wheel drive light is to alert the operator the system is not being read properly by the ECU.

If the ECU loses contact with or position of the Transfer case actuator motor the service light will come on. Same thing goes for the front diff actuator.

So it may be a bad switch, sensor, or an actual problem in the 4WD linkage. This is not a Oil Change light that you can ignore a few extra weeks - it indicates a problem that should be taken care of ASAP to avoid costlier problems down the road.
Thanks for using FixYa - a FixYa rating is appreciated!!

Feb 21, 2009 | 2004 Chevrolet Suburban

1 Answer

1993 Chevy 1500 pickup 4-wheel drive

I replaced the malfunctioning “thermal actuator” with the “Warn” Vacuum actuator setup, it’s been working great for about 7 years now, simple install, if I remember correctly, it was about $150.
That’s what engages the front diff into 4wd.

Nov 24, 2008 | 1993 Chevrolet C1500

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