Hello,

New guy here. I just acquired a 1997 Blazer LS. Today, third day driving it, I got on the highway. At 70 with the cruise engaged. Had to slow for traffic ahead, and tapped the brake pedal....

This loud growling noise appeared which sounded like I was on the rumble strip, but not quite that bad. I immediately pulled over to the shoulder and the noise continued until I got to about 5mph, then I felt a "clunk" and it stopped.

Sat there a minute, with my wife looking at me like "what the hell was that?"

I started back on the highway. Once reaching 70 mph, I slowed (no cruise) and it did it again. So I kept driving and it would subside under load (power) but come back on deceleration. Again, the "clunk" as I stopped at the end of the off ramp and no more trouble at 45 mph on county roads.

So, the way home I kept it at 60 to 65 and no trouble.

I've been reading my butt off on all sorts of forums (you guys are great BTW) and it seems to be a vacuum problem at either the actuator, cable, or switch. How hard is the T-case switch to change? I have the three button system. 2hi, 4hi, 4low. Also, I did read about the TCCM troubles with corroded terminals (it's under the kick plate on the passenger side). I don't think I have that trouble yet. Errant 4WD engagement and odd lights on the buttons are not the problem.

I'm a decent wrench, this is my first Blazer (it's got 186k on it) and I owned a '99 Explorer before this. My wife totaled it, I'm poor, and this is all I could afford with the insurance check.

Tips on diagnosis so I don't replace needlessly, would be appreciated.

TIA,

JamesK

 

It definitely sounds like you have a problem with your vacuum switch on the transfer case. One way to confirm is to disconnect the vacuum line to the actuator (located under the battery) and plugging it with a golf tee. Now drive the truck and see if the problem persists. If it does not, then you know that vacuum is getting to the front axle actuator from a faulty switch.

BTW, I have removed your reply to another thread due to this thread.

 

Thanks swartlkk!

Sorry about the hijack and double post. Thanks for the "test" method. I will certainly try that.

I found the actuator at the Zone, but the T-Case switch is dealer only? Any PN's that you know of, or secondary market sources?

I like the truck, expect problems of course, it's age and mileage. Dome light is always on, had to remove the bulb. You know where to get the remote mirror switch? Mine is dead....

 

The vacuum switch is not dealer only. Motormite PN 49315 is available for $15 from Advance Auto.

As far as your dome light is concerned, you likely have a door switch that is not breaking the connection properly when the door is closed. That can be a challenge to diagnose, but it starts with disconnecting all of the door switches at the same time to see if the dome lights then go off.

 

Just wanted to let you guys know that the problem was indeed the vacuum actuator switch.

I did pick up the motormite part from Advanced Auto. Interesting that it's in the "Help" area where door handles and the like are found.

Must be common.....

Thanks for the input!

JamesK

 

Glad to help! Good to hear it all worked out for you!

 

Just had the same problem. Disconnected the actuator and plugged the vacuum line with a golf tee. The noise is gone. Looks like im off to go get a vacuum switch. By the way. Is this switch hard to replace? I.E. where is it located? Wish I knew this this morning when I replaced my shifter cable when i was already under there with the skid plate off and the car on jack stands. Oh well, just glad to have the problem resovled. Got the part number from this thread so I know what to look for. Thanks again Blazerforum!

 

furious,

It wasn't hard really. Mine was located on the top left (driver) side of the T Case near the back. You'll see the three pronged connector with vacuum lines to it.

I used a box wrench (7/8"? can't remember) angled down. Hardest part was getting the new one back in straight, you can't see the hole so it's by feel.

Try and clean all the grit and grime away from the area first. I sprayed it with brake cleaner (be careful!) then compressed air before I removed the old one. There was a fair amount of 'crud' around it and I didn't want that getting into the T Case.

James