What Could Cause This Problem?

[JN2001]

So I'm driving my 2001 Silverado 4x4 down the interstate this morning taking the kids to my parents and intermittently, my truck feels like something is engaging. It seemed to happen when I would hit bumps and kind of feels like there is a drag for a little bit, then it goes away for a while then comes back again etc. At first I was thinking tranny problems but I am more leaning to a brake grabbing or hub problems? I have been noticing a slight hum lately but I was initially thinking it was just tire noise.

 

Any suggestions??? It has 126,000 miles on it. I've only owned it since around 100k so don't know all the history before but since I owned it, have replaced all fluids, filters, belts, tires, fuel pump, water pump, upper and lower hoses, plugs, rear brake pads, emergency brakes, rear rotors and was getting ready to replace my inner left side axle shaft seal that is leaking.

 

Thanks for any help you can provide!

[gvbhunt]

I do not know if it would be the same thing but we had a 2002 Chevy Trailblazer 4x4 and it would do that. Driving about 65 on the highway and it felt like you hit a big snowdrift or something. The dealer determined that it had to do with the 4x4 selector switch shorting out internally and causing it to randomly engage the front end.

[JN2001]

I do not know if it would be the same thing but we had a 2002 Chevy Trailblazer 4x4 and it would do that. Driving about 65 on the highway and it felt like you hit a big snowdrift or something. The dealer determined that it had to do with the 4x4 selector switch shorting out internally and causing it to randomly engage the front end.

 

Hmmm. That's a good way to put it. It does feel like you hit a snowdrift, then drove out of it and periodically hit more. I wonder if I can either disconnect the switch or pull a fuse or something and go for a drive to see if it does it or if that will that mess something else up?

[gvbhunt]

I do not know what the effect of pulling a fuse or something like that would be. Possibly cause it to start throwing up engine codes because something is not connected. Maybe you could try (granted the pavement is wet or snowy) driving it in 4x4 on the highway and see if it still does it? Maybe it would not do it if it was already in 4x4. Can you watch the selector (or better yet have someone watch it for you while you drive) and see if the thing shows going into 4x4? I sort of remember seeing the light flash or something. I never had a chance to really diagnose the problem on the trailblazer as the wife veto'd my attempt to look at it myself....It was her car though.

[JN2001]

I do not know what the effect of pulling a fuse or something like that would be. Possibly cause it to start throwing up engine codes because something is not connected. Maybe you could try (granted the pavement is wet or snowy) driving it in 4x4 on the highway and see if it still does it? Maybe it would not do it if it was already in 4x4. Can you watch the selector (or better yet have someone watch it for you while you drive) and see if the thing shows going into 4x4? I sort of remember seeing the light flash or something. I never had a chance to really diagnose the problem on the trailblazer as the wife veto'd my attempt to look at it myself....It was her car though.

 

I checked and the selector light doesn't seem to be switching from 2wd and there isn't any snow currently for me to test it in 4wd. I may have to do a little more research on how to test the hubs to see if they are good or bad. I seem to remember a hub problem on a previous vehicle several years back that I think acted similar. I'm hoping it is something other than the tranny.

[michigansilver03]

Did you have the windshield defrostor on

[silveradocoa]

a/c on? compressor kicking in? that is a lil weird

[JN2001]

gvbhunt, I think you were right. I jacked up the front end and everything felt tight so yesterday, I ended up pulling the fuses for the 4x4 (inside truck) and transfer case (engine compartment). I do get the service 4x4 light of course but I took it for a drive and it didn't act up. I drove it again this morning on the interstate for a while and still no problems. I think I will replace the switch and hopefully it will solve the problem. The only thing I worry about is if the problem is somewhere else in the 4x4 system but I'm not sure if there is any way to tell that other than eliminating the switch first.

 

I'm not sure if I had the defrost on or not when that was happening so I might have to take it for a drive with the defrost on and the 4x4 fuses still out and see if it happens.

[JN2001]

Ok, so now I'm not sure what the problem was. I put the fuses back in and drove it and it ran perfectly. I don't know if pulling the fuses reset something or, if it had something to do with moisture. The morning it happened it was misting out and today it is clear and sunny. I guess I'll just drive it and see if it happens again next time it's wet out and go from there. Thanks for all your help! This site is a great!

[Rob M]

Torque Converter going in and out of lock up? If the problem comes up again see if the rpms jump or fall while this is happening.

[JN2001]

Torque Converter going in and out of lock up? If the problem comes up again see if the rpms jump or fall while this is happening.

 

It hasn't happened again but I will check that if or when it happens again. I'm keeping my fingers crossed hoping it doesn't come back. Thanks for the info!