87 blazer 4x4 help - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 10-08-2000, 12:01 PM
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87 blazer 4x4 help

my 4 wheel drive will not go in 4 hi or 4 lo my light stays on in 2 wheel drive can some one help me? does anyone have a pic of the vacuum sys. i need all the help i can get
thank you

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post #2 of (permalink) Old 10-08-2000, 01:26 PM
 
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Re: 87 blazer 4x4 help

How do you mean it will not go into 4 hi or low? Do you mean the lever will not physically move to those positions, or do you mean you can move it to those positions but it still won't engage the 4 wheel drive?

To test the vacuum actuator mechanism, take a vacuum pump (or a clean hose) and attatch the hose to the vacuum port on your vacuum actuator, which is located on the passenger side fender or under the battery tray (my 85 has the actuator right up on the fenderwell so I'm not sure which location yours will be in)... If there's any doubt as to where your vacuum actuator is, you can look under the truck at the front differential, and find the cable sticking out of your differential, if memory serves me correctly it'll be in the passenger side of the differential. Trace this cable and it'll lead you to your vacuum actuator. Draw a vacuum on the actuator and check whether it moves in, it shouldn't take too horribly much vacuum to pull it in. If the diaphragm does move in, then look at the cable, and ensure it moves with the diaphragm (there's a little clip that holds the cable to the actuator diaphragm that could have fallen off, and could prevent the actuator from engaging the front diff)... If the cable doesn't move, then try pulling on it in the direction of the diaphragm travel. If the cable doesn't pull freely, then you'll have to pull the cable from the front differential, and make sure you lube everything up in there.

If your actuator and cable mechanism engages the front differential with the help of the vacuum pump or your lungs, then your problem resides in the vacuum lines leading to it. You should not need a vacuum line/hose routing diagram for this part if the hoses are already in place... Just check them for cracks and or tears/melting... If they seem old, replace them, simply feel around and plug the replacement hoses into the port you got the other hose off and test it. If the 4x4 fails to disengage then the problem is the vacuum switch on the t-case...

I haven't seen a good diagram of the vacuum lines, so if anyone has one please post it... If no one has one, I'll go out and do some looking at my truck, they should be similar... But either way, the diagram will be one of the final elements I'll need to produce an article on troubleshooting the 4x4 system on these trucks for the ORC Chevy/GMC page...

Good luck, I hope this helps at least a little...

Oh one other thing, what transfer case is it? There will be a tag screwed into the back of the t-case, that info is on there...

Tim
ORC Land Use columnist
My August article on ORC

http://www.off-road.com/land
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post #3 of (permalink) Old 10-08-2000, 01:55 PM
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Re: 87 blazer 4x4 help

thanks for the replie!
it well move to those positions but well not go in i do not have any vacuum when i unplug the line from the actuator.
i do not know what transfer case i have but i well look at it and let you know! thank you for you help i need all the help i can get ! if it is the switch how do i get to it?

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post #4 of (permalink) Old 10-08-2000, 08:11 PM
 
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Re: 87 blazer 4x4 help

The first place I'd probably look for the (no vacuum at the actuator) problem would be the vacuum hose that goes from the intake manifold on the engine to one of the ports on the transfer case. The port on my intake manifold is behind the carb (is yours TBI?, probably the same place for TBI and carbed)... Last time I looked at mine, it was dangerously close to the exhaust manifold (until I rerouted it somehow, if memory serves me correctly, I pull tied it onto either the frame or the crossmember, I'll try to check on that some more)...

Tim
ORC Land Use columnist
My August article on ORC

http://www.off-road.com/land
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