Trying to figure out why my 4 wheel drive will not engage on a 1989 Chevy S10 Blazer with 4.3L TBI engine and 700R4 automatic transmission. When I put the truck in 4 high or 4 low nothing happens. The 4 wheel lights don't come on the floor panel and the transfer case does not engage. What should I do first to troubleshoot this problem. I've taken the battery box out and observed the vacuum actuator. Nothing happens when 4 wheel is engaged. I can move the actuator freely with my hand and I can hear a click where the cable goes into the transmission but still nothing engages. I getting ready to check the vacuum actuator switch on the crankcase to see if it is defective. Any other suggestions would be greatly appreciated.
The vacuum switch on the transfercase is most likely the problem. If you remove it and the plunger is stuck in, replace it and your 4wd should engage again.
I have tried all kinds of things to get my 4x4 to engage and still nothing can anyone help
The modulator at the transfer case probably stuck and may need service or replacement use a rubber mallet and hit actuator where it bolts to case careful dont hit connector and try if moves than remove and lube actuator shaft if dont move than remove and check shaft for bent or damage a lube shaft with out try to shift to 4hi if actuator activates and shaft does not move most likely replace but have part checked by auto store first
Theres a vacum line look under ur frame for loose hose from the transfer case .
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