98 Blazer 4x4 problem

jtpannell · #1 03-23-2005, 05:07 PM

In 2-HI My Blazer makes loud hum on front right side. I can switch to 4-HI and the noise stops. When I put it back in 2-HI there is no noise for a minute or two, but noise eventually starts again. The noise is a rubbing noise. I have read about the wheel bearing going out. but it doesnt make noise in 4-HI or 4-LO. Please reply if u have any clues. Thank You.

BlazerLT · #2 03-23-2005, 05:10 PM

Is it a metal scraping noise?

Also, have you recently put new front brakes on?

swalt · #3 03-23-2005, 06:48 PM

Covered many times here. Most likely your vacuum switch on top of the transfer case is defective causing the diff to partially engage. If that is not the problem, your actuator cable is binding and is staying locked in 4WD and then as you drive it is slowly disengaging. With mine, the humm was extremely loud from the right side and as I pulled to a stop I had a loud ratcheting/clicking noise which was the gear on the axle shearing.

jtpannell · #4 03-24-2005, 08:39 AM

Quote:

Originally Posted by BlazerLT

Is it a metal scraping noise?

Also, have you recently put new front brakes on?

Thank You for replying, It is not a metal scraping noise, and I know there hasn't been front brakes put on for at least 10,000 miles, because thats how long I've had it.

jtpannell · #5 03-24-2005, 08:44 AM

Quote:

Originally Posted by swalt

Covered many times here. Most likely your vacuum switch on top of the transfer case is defective causing the diff to partially engage. If that is not the problem, your actuator cable is binding and is staying locked in 4WD and then as you drive it is slowly disengaging. With mine, the humm was extremely loud from the right side and as I pulled to a stop I had a loud ratcheting/clicking noise which was the gear on the axle shearing.

Thank You for replying. I do not hear a loud ratcheting/Clicking noise when I pull to a stop. I can also hear the 4WD disengage when I switch to 2WD. But I will look into the vacuum switch on top of the transfer case. Is this hard/expensive to replace? Thank You very much for your input.

swalt · #6 03-24-2005, 10:26 AM

The vacuum switch is relatively inexpensive and easy to change. Directly on top of the transfer case. In my case the humm happened a few times over a period of two years and usually happened in very cold temperatures after extended highway driving. I think mine went to long and eventually caused the damage to the axle shaft. When I get a chance, I will post pictures of the internal components that were damaged (the gear was the worst). I also have a video clip with sound of the humm and the ratcheting which I will drop on my website for viewing.

jtpannell · #7 03-24-2005, 10:47 AM

Quote:

Originally Posted by swalt

The vacuum switch is relatively inexpensive and easy to change. Directly on top of the transfer case. In my case the humm happened a few times over a period of two years and usually happened in very cold temperatures after extended highway driving. I think mine went to long and eventually caused the damage to the axle shaft. When I get a chance, I will post pictures of the internal components that were damaged (the gear was the worst). I also have a video clip with sound of the humm and the ratcheting which I will drop on my website for viewing.

Mine does it every time I try to drive it. Do you still think it could be the same problem? It did it once a few months ago, but I drove a few feet in reverse, it stopped, and had not done it since until 5 days ago. I spoke to a mechanic and he mentioned a bearing, but he has not seen nor heard it himself, and I do not want to pay him a few hundred to tear it all apart. Thank you again for your time and input. Please let me know your web site address when you can. Thanks again.

jtpannell · #8 03-29-2005, 12:50 PM

I previously posted a thread about my blazer making noise in right front when in 2HI. The noise goes away in 4WD. When I put it back in 2HI it will be fine for couple blocks, sometimes a mile or 2, but it always goes back to the noise. I've been told to check the vacuum actuator switch.

BUT a few days ago I checked transmission fluid, it was only up to the cold area of the dipstick. I drove it to work yesterday and when I got home checked it again and it bearly fills the eyelet at end of dipstick. There are no puddles in my driveway or in my parking spot at work. The only leaking I noticed was when it was parked for a week there was a 3 inch puddle and thats it. Also this is not a slow leak I checked fluids a couple months ago and it was fine. ANY INPUT PLEASE!!!!!!!!??????

Please do not reply BlazerLT!

ricksza · #9 03-29-2005, 07:57 PM

I've seen transmission fluid sucked out of the transmission through the transfer case vacuum switch. There is a vacuum servo under the battery. With the engine off, try to disconnect the hose off it and see if there is fluid in the hose. You might be able to reach it without removing the battery and tray.

DJSteve · #10 03-29-2005, 08:32 PM

Have you checked the fluid level in the transfer case? I'm not sure it would be related to your noise problem, but there is a seal between the trans and transfer case that keeps the atf and gear oil separate. If it went bad in a major way it might account for the loss of fluid. Long shot maybe, but pretty easy to check.

DJSteve · #11 03-29-2005, 08:38 PM

And when you're talking about the noise on the right side, can you tell where it's coming from? If it could conceivably be near the wheel your problem might be a bad CV joint in the right axle. When there's power going to the wheel the CV joint is loaded differently than when there isn't. How many miles are on it? If it has quite a few this could conceivably happen without the boot being cracked. And if there is a cracked boot you probably found your noise problem.

BlazerLT · #12 03-29-2005, 09:00 PM

Quote:

Originally Posted by jtpannell

Please do not reply BlazerLT!

What is your problem?

What the hell did I do?

jtpannell · #13 03-30-2005, 11:11 AM

I've seen transmission fluid sucked out of the transmission through the transfer case vacuum switch. There is a vacuum servo under the battery. With the engine off, try to disconnect the hose off it and see if there is fluid in the hose. You might be able to reach it without removing the battery and tray.

Have you checked the fluid level in the transfer case? I'm not sure it would be related to your noise problem, but there is a seal between the trans and transfer case that keeps the atf and gear oil separate. If it went bad in a major way it might account for the loss of fluid. Long shot maybe, but pretty easy to check.

Thanks for the replies.
Do you think it could suck 2 or 3 quarts of atf out in either one of these scenarios?

wolfox · #14 03-30-2005, 11:13 AM

Quote:

Originally Posted by DJSteve

there is a seal between the trans and transfer case that keeps the atf and gear oil separate.

Dextron III ATF is what fills both the transfer case and the transmission on our trucks.

However, in a 98 truck, there *might* be AllTrak-II fluid in the transfer case if it was made with a revised clutch design. Nothing short of pulling the upper plug and getting a look will tell for certain. AllTrak-II's a blue synthetic fluid. There is certainly no gear-lube/oil in our transfer cases if they are second generation or later Blazers.

DJSteve · #15 03-30-2005, 11:46 PM

wolfox- Thanks for keeping me honest. I haven't owned mine long enough to check the transfer case, because the trans shat a month after I got it and the shop I took it was kind enough to drain and refill the transfer case as well. They said the seal between the two on mine was leaking and that it could cause problems... so I assumed they two used different fluids.

So what's anyone think about the noise possibly being a CV joint?

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