Four wheel drive problem

DOUGHSP

MEMBER
CHEVROLET

1997 Chevy Blazer 148,000 miles. My front wheels will not engage in 4hi or 4lo. The front drive shaft will engage and the vacuum actuator moves but is sticky and does not move smoothly. The front diff was low on fluid so I drained and refilled. My first guess wold be the actuator. What does the switch on the front diff do? Also, 90% of the time all lights (head, interior, dash, fuel gage movement) pulsate. It gets worse with increase of RPM. It has done this for years. Could it be the voltage regulator?

4 Replies

2CARPRO JACK

MECHANIC
11,533 POSTS

Could be the voltage reg. Check all ground and power wires for good clean connections. The 4x4 problem is the actuator. GM had alot of problems with it especially in cold weather. The updated oart has an integral heater in it. They are easy to install and wire.

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Tuesday, December 19th, 2006 AT 7:37 AM

JSTEINDL

MEMBER
10 POSTS

I agree with the acctuator being your 4x4 problem. As for the pulsating of your lights etc, have your alternator checked. My 98 silverado did the same thing. Had a bad alternator. Another common problem in GM's.

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Friday, December 22nd, 2006 AT 4:09 AM

DOPEY

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4 POSTS

I replaced my accuator, but it always stays depressed unless I disconnect the vacuum line. And it doesn't go all the way into the 4x4 just makes a mild clanking like its just barely in 4x4

I don't know what controls the vacuum. I tried pulling on the cable and I can't pull it far enough to engage the 4x4 either?

Any advice?

TIA

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Wednesday, October 31st, 2007 AT 8:34 PM

DOPEY

MEMBER
4 POSTS

I replaced my accuator, but it always stays depressed unless I disconnect the vacuum line. And it doesn't go all the way into the 4x4 just makes a mild clanking like its just barely in 4x4

[update] I had to replace the vacuum switch on the transfer case, now the acuator works fine.

I don't know what controls the vacuum. I tried pulling on the cable and I can't pull it far enough to engage the 4x4 either?

Any advice?

TIA[/quote:ece86527b0]

[update]
I have a 1996 Blazer 4x4 with manual shift 4x4 (not dash button) my differential is not engaging as it should.

The vacuum acuator was bad, replaced. The vacuum switch was bad, replaced. The cable may have been bad, replaced.

I took the cable off at the housing on the differential and removed the housing face plate. I used a pair of vise grips to pull the acuator out to engage the 4x4 but all it would do is grind mildly, all it would do is grind mildly when I had it all
connected too.

So I have traced the problem to the differential. I cant seem to engage the "collar" for the axles to engage.

I just don't know what to do from there? Any ideas would be appreciated.

TIA it's appreciated.

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Thursday, November 1st, 2007 AT 7:04 PM