4-wheel drive making some noise

[Uh-Oh]

This isn't always a problem for me, just sometimes it happens. Just when I have to use 4x4 for a bit, which I would use it a whole lot more if it didn't have this problem when I did use it.

Ok, when I use 4x4 on my 2001 blazer, it always goes in and out smoothly, or appears to anyway. It makes no funny noises and it right there when I need it. The problem comes later, an only happens when I do use 4x4 that day.

After having the blazer in 4x4 say in the morning, I can be driving later in the afternoon long afterwards and start experiencing a strange problem. I will be cruising along at highway speed, going up and downhill as we have a lot of them here in Southeast Kentucky. Then once I crest the top of a hill at highway speed I'll hear a loud whine start coming from the front end, actually kind of sounds like its comes from the passenger side of the front end.

When it starts the whining I pull over and start slowing down on the shoulder, the slower I go the more it sounds like a baseball card on a bicycle rim. If you have ever heard a manual hub go bad, it sounds like that. I thought it was the hub at first, but from what I can tell the blazer doesn't have a hub, the axles look like that stay locked in all the time and the mechanism to connect them to the 4x4 is in the front end, I could be wrong though.

Anyway, once I slow down to under 5mph whatever is making the noise kicks out. I can usually stop and put it in and out of 4x4 a couple times and go until the next time I have to use 4-wheel drive before it starts to do it again. I can't figure out what the problem is with it.

Do any of you have any ideas? Do I still need to include more info?

Basically it does it only after I've had to actually use 4x4 to get up a hill or through some mud, or back a small ATV trailer up the driveway. Then it only happens at highway speeds while cresting over the top of a hill when I let off the gas to coast down the other side. Sometiems it does it sometimes it doesn't. It sounds bad when it happens, and I would like to be able to use my 4x4 trouble free.

[Mikado14]

I most certainly do know what you are talking about. It is your front axle disengaging and I bet you are going over 60 mph when it happens.


Is your Blazer mechanical or push button?

[Uh-Oh]

You are correct in that I am going over 60mph when it happens, that's what I was meaning by highway speeds. My blazer is a push button one.

I can drive around all day on the roads nearby home and about as fast as a person can get on those is about 55 and only for short runs, but when I get on the highway and get up to good speeds for a good run it will start it.

You know how to fix this problem?

[Mikado14]

Originally Posted by Uh-Oh

You are correct in that I am going over 60mph when it happens, that's what I was meaning by highway speeds. My blazer is a push button one.

I can drive around all day on the roads nearby home and about as fast as a person can get on those is about 55 and only for short runs, but when I get on the highway and get up to good speeds for a good run it will start it.

You know how to fix this problem?

This is the culprit is most instances. The only problem is I am not sure if the 2001 still uses this switch. If you have one, it is on the drivers side top of the transfer case. Look under the battery on the passenger side to see if you have the vacuum operated actuator. There will be a cable running down to the front axle. If you have it, then this is your problem.

The switch on the left is good and the switch on the right is bad. The pintle will stick and apply vacuum to the front axle and either partially or fully engage the axle when you are not in 4WD.

A temporary fix is to find the line to the front actuator and remove it and plug the end of the hose. This will keep the front axle freewheeling until you replace the switch.

[Uh-Oh]

I'll check that out and see if that is the type of system I have, I'm just glad that I have a direction to go in now. I'm not very familiar with the blazer 4-wheel drive system. The only type I'm familiar with is on an old 78 Jeep CJ that I had, no electrics to it at all. Just lock in the hubs and pull the transfer case in to 4x4 and you were done. I've not owned a 4x4 is so long that I've forgotten about all that I ever learned about them.

[swalt]

I have my truck into the shop for the exact same reason right now. You described the problem to a T. My vehicle has been in the shop for two weeks now as the aftermarket warranty is refusing to cover the damage. The clicking noise you hear as it is slowing down is the gear chewing. My problem also occurred only in cold weather. My warranty company claims the actuator cable was binding although it has been pulled out of the vehicle and is moving freely. They now claim it is stretched. I'm looking at about $1000 in parts Canadian for a new shaft, gears, washers, etc plus 5-6 hours labour. The casing was full of filings and most of the internal components are either stripped or scored.

[Uh-Oh]

I hope that I can get mine fixed before I run into a lot of extra repair bills. My experience with this blazer has been pretty bad so far, and I'm doubtful that my next vehicle will be a chevrolet.

My last couple vehicles were fords, and they broke down as well, but the customer service was worlds beyond what I've been getting with chevrolet.

[BlazerLT]

Are you using 4x4 on a dry road at 60mph?

[Uh-Oh]

Originally Posted by BlazerLT

Are you using 4x4 on a dry road at 60mph?

No. It happens when I've used 4x4 earlier in the day, and then later get on the highway. It is in 2 wheel drive when it does it. Then it only does it when I crest over the top of a hill and let off the gas to coast down the other side.

[swalt]

As I mentioned, mine is in the shop for the same problem. I have two videos I captured on my digital camera of the sound happening and showing the sound disappearing as it is engaged into 4HI. Also have a video outside of the vehicle capturing the clicking noise as it was coming to a stop. That was the gear getting chewed. The dealer replaced my vacuum switch about 3 weeks ago thinking it was sticking and the front axle was engaging itself. Problem happened again on the 13th of November after the switch replacement and thats when I was towed in and the truck has been in the shop ever since. They are still arguing with the warranty company that the washer/gear failed on the axle. Warranty company says the cable from the actuator binded (and they don't cover consequential damage due to linkages) causing it to partially engage. I will try and snap some pictures next week of the damaged parts and post them to my web page so you can see what you are looking at. If you want me to email the videos of the truck making the noise to confirm it is the same as yours, just PM me, but by your description we are in the same boat.

[BlazerLT]

This sounds like the transfer case is not disengaging.

[swalt]

Originally Posted by BlazerLT

This sounds like the transfer case is not disengaging.

I thought about that, but in my case it would happen without 4HI being engaged previously so that would eliminate the transfer case. I have gone weeks without engaging the 4WD and as soon as I take a highway trip, about 100km's in it would start to howl. The cold also seems to be a factor in my case as it was only occuring below zero. Thought maybe there was moisture in the diff and it was freezing up, but drained the diff and re-filled and it did not make a difference.

[BlazerLT]

Just because you haven't gone to 4x4, doesn't mean the transfer case could be starting to partially engage.