1987 S10: 4 wheel drive not working

2 wheel drive is fine, but my 4 wheel drive is not working. I go into neutral on the steering wheel while stopped. Then move the floor shifter from 2 wheel to 4
wheel which is the correct procedure,
The light on the floor shifter goes on saying its 4 wheel drive. I get a vibration on the highway when going over 40 mph and thats about it.
I checked the wheels while they were spinning in snow an the two front tires are stationary.
Neutral works on the floor shifter and I hear some grinding of gears occasionally from the floor shifter.
also when going from 4 wheel to 2 wheel via the floor shifter,.. then moving/shifting the steering wheel shifter out of nuetral into drive there was no engagement. A gear grinding noise so immediately I shift back to neutral then after a few trys I usually get back into Two Wheel drive.
Just started noticing this yesterday thanks to a snow storm out here in Massachusetts.
Anything sound familiar here?
Thanks
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There is a Vaccum Switch on the Tranfercase... Right side WAY up on the TOP
This goes Bad OFTEN
DEALER only part ( $18.00) The Vaccum Hoses at this switch are quite Close to the Cat Converter and they Dry out and also CRACK..or BREAK
These Hoses Route The Vaccum to a Canister UNDER THE BATTERY in the hood compartment.
Now This Canister Has A Cable Running out it to the FRONT Drive to engage The Gears for 4 wheel operation.
My Son's 87 Had BAD Hose's at the Switch and He had No 4 X 4 operation till we repaired the hoses and Replaced the Switch since Dirt got into the Switch !!
Kevin Duggan wrote:

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Fantastic,..Thanks
I went to the Auto Parts store today, they were telling me about the daiphram under the battery also,..
thanks for your help.
What would be a good manuel for me.
Basically a beginner
Again Thanks
Kevin

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Kevin Duggan wrote:

you can Pull that Cable BACK and Hold it with Vice grips Then Test drive to see it is in GEAR,
also u can pull off the Vaccum hose and see if You are getting Vaccum ... If Not, It is the swithch on the Transfercase or Your VACCUM Hoses are BAD..
Also The VACCUM ports on the engine are Noted for PLUGGING with Carbon,
I Clean my ports out with a DRILL BIT.. of Which I turn with my Fingers,, No DRILL MOTOR INVOLVED
,

Well Chiltons and Motors Manuauls Are of No use Today.. Back in the 50's and 60's they actually Helped A lot, But now-a-Days, They are not worth Buying..
You can go to your local Library and see if they have these manuals or You can Buy The Actual Repair and and Diagnos manual from your GM dealer.. But be prepared to have lots os $$$$ with you!!

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damn, sounds like the same problem on my 98 Sonoma
J
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<<<The light on the floor shifter goes on saying its 4 wheel drive>>>
If the vacuum switch, hoses, or the diaphragm were bad the 4X4 light should not be lit---my 2 zents worth
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There are two lights. The little dots beside the 2hi, 4hi, neutral, 4lo words which would light according to lever position, regardless of if the diff is engaged or not. The second is the top half of the little drivetrain diagram, that will only light if the diff is actually engaged.
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snipped-for-privacy@aol.com wrote:

On my 1994 s10 blazer with the elec. switch. I had a bad diaphragm(under the battery) the light would still light up. I thought i had 4x4 until i almost got it stuck on the farm. traced the hoses to find it torn.
miked
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I see the lights on the floor shift going off when I accelerate while in 4 wheel and going back on when I slow down.
This seems to be the pattern although I have not spent all that much time in 4 wheel.
I just ordered a manuel on Amazon last nite.
I have to go pop open the hood and hopefully have a idea about what is going on.
I like the idea of working on cars but not too much knowledge,
thanks
kevin

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The diaphgram unit is under the battery, but from the sound of it (indicator light going on and off) I'd place my money on a bad vacuum switch which is on top of the transfer case with three vacuum hoses on a triangular shaped rubber plug...an easy way to test---- figure out which one runs to the diaphgram, apply a vacuum and see if the light comes on and stays on.
If I remember ya gonna need a 1" deep (or was it 15/16?) socket to get it off
Been that and dun dat...after slippin' all over a snow covered road while thinkin: "I'm cool I got 4WD!"..NOT
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Thanks;
That was me yesterday trying to get out of the driveway. Good news is ,..the winter is just starting .
to some I suppose thats bad news though
but,... Thanks a million for the help
Kevin
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