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post #1 of (permalink) Old 12-15-2004, 01:09 PM
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91 Chevy will not go into 4 wheel drive

I've got a 91 chevy 2500 4x4. When I shift the lever in the floorboard to 4H or 4L it doesn't go into 4 wheel drive. It was working fine a few weeks ago. The shifter goes from 4H and 4L just fine, it's just the front wheels never engage. I've checked the fuse and it is fine. Some people said it was the Actuator so I've replaced the Actuator on the front transfer case but that didn't solve the problem. Anybody got any other suggestions as to what it might be before I take it to the dealer and spend tons of money on it?

Thanks, Mark
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post #2 of (permalink) Old 12-15-2004, 06:38 PM
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Re: 91 Chevy will not go into 4 wheel drive

A few thoughts,
What is telling you your not in 4WD?
Is it going into low range really? (not just shift lever in low range position)
Did you have the old actuator tested NG?
Did you have the new one tested before installing? I replaced mine many miles ago and the new one worked one time before shorting out. So can can get a bad one.
Did you check for voltage at the actuator? Switch at the shifter?
From what you describing it does sound like the actuator but apparently it isn't. First thing to check is good voltage all the way to the actuator and ohm test the actuator.

Good luck
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post #3 of (permalink) Old 12-16-2004, 09:44 AM
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Re: 91 Chevy will not go into 4 wheel drive

it's going into low range because when I put it into 4L I drive it and it is in low range, but the front wheel aren't pulling.
thanks for the advice about testing the voltage all the way to the actuator, i think that is the problem. last night i took the actuator off and put a small rod in the transfer case and pushed the button that the actuator pushes and the 4 wheel drive light came on in the floorboard of the cab. I didn't have time last night to track the voltage all the way to the actuator.
there's also a little switch on top of the transfer case that is activated by the 4 wheel drive lever in the floorboard, it might be bad too.
i'll see what i can find out.

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post #4 of (permalink) Old 12-16-2004, 10:51 AM
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Re: 91 Chevy will not go into 4 wheel drive

the way you test the actuator is to engage 4wd and actually watch the actuator extend (or not if it is busted). the actuator is in the front differential. take a crescent wrench, set it to mmmm, around 3/4" and unscrew the actuator. leave it plugged in so you can test it. don't fprget to have a rag handy. you'll get a little gear oil spill when you pull out the actuator from the diff.

i don't understand what you did with this "putting a rod in the transfer case and pushed a button that the actuator pushes". why would you be sticking rods in the tcase?

the 4wd indicator switch is located on the differential too. it is screwed in. if you take it out, it is just a little spring loaded buton that comes on when it is activated by the gear pressing on it inside the diff. i had this go bad on my truck. the button got a little crooked in there, and it jammed up and would not allow the gear to disengage the axles, so my front was stuck in 4wd even though the tcase was in 2hi and i had no inidicator lights.
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post #5 of (permalink) Old 12-20-2004, 09:52 AM
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Re: 91 Chevy will not go into 4 wheel drive

I got it worked out. The problem was both the Actuator and the Shifter Switch were bad. I tested the new Actuator wehn it was on the truck by bypassing the Shifter Switch. I then purchased a new Shifter Switch and hooked it up, and everything worked fine.

Thanks for the help.

post #6 of (permalink) Old 12-20-2004, 01:23 PM
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Re: 91 Chevy will not go into 4 wheel drive

i was gona say to bypass the shifter switch with a toggle switch.

this saves alittle money and gives you option of 2low.
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