I am a new member here hoping to find some help on the 4wd on my zr2. I've had this truck about 4 months and when I first got it it was making a whining/grinding noise but more of a whining noise from the front end but it only did it every once in a great while and all you had to do to get it to quit was stop at a stop sign or hit the 4wd button and shut it back off and the noise would go away. Somedays it would do it somedays it wouldn't do it all, but then it got worse and it wouldn't make the noise unless you had it in 4wd full time it wouldn't make the noise, then it got to making a banging felt like you were hitting a bump kinda noise in the front end when it was in 4wd but it only would do it when u were accelerating from a stop up to about 40 mph then it would stop going down the highway till you stopped and sped up again. I took it to a shop and he just put a new actuator in it yesterday and that didn't fix it. I was wondering if anyone here had any ideas what was causing this so maybe I could tell the mechanic so he would have a little more of an idea what to look for. I really hope someone can help me on this. Thank you very much.  

you could have a bad hub asm, frt diff problems, or t case mode actuator problems. i would take it to a reputable gm dealer in your area,bite the bullit,get it fixxed right, and ask for a tech who knows the s10 pickup 4wd system because they are a diff animal. A shop is not going know them that well and will throw parts at it just to get your money and unhappiness. good luck because the zr2 is fun out on the trails, not the shop  

Did you ever change fluid or check levels in Tcase and front drive axle after you got truck. This is kinda the first thing you do with any used vehicle, especailly a 4x4.  

the dealership where I bought the vehicle said they checked all the fluids on the vehicle before I picked it up.  

The shop where it's at now is a 4wd and automatic transmission shop.  He put an actuator on it and that didn't fix it cause that's what he orginally thought.  He said today the hubs cv's and everything was alright.  the transfer case is kicking in and out and works good.  he thinks maybe it is a vacuum problem.  We are going to give him till tomorrow then we will take it to the dealership where I bought it normally this guy is really good and we like him a lot and he's cheaper so we thought we'd take it there.  

The dealership may have a bunch of parts changers and no one who actually knows how to fix it, (I worked for one) that gets spendy, they have a book of excuses for changing every part that didn't need to be replaced, I'd be more paitent with the tranny man. still could be a hub problem, broken or worn actuator pin or the switch on the t-case, what about the indicator lights, do they come on when the t-case is put in and out? I'm not so sure that the 03 even has a vacuum control on it, especially if the actuator is electric. the older ones had a mechanical vacuum actuator, I had one with bad hoses and stuck a stick in the vacuum diaphram to keep it engaged, the redneck thing to do with no money.  

yea the 4wd lights come on in 4hi and 4lo the 4wd will actually work in hi and lo but it makes a banging noise when you speed up to about 35-40 mph then it quits makin the noise.  We'll see what happens.  

that must be something in the hub locking mechanism, it could be jumping in and out, maybe rounded off. loose connection causing the actuator to misfunction. beings to how the light is working the t-case switch must be ok??  

The actuator on that SUV is vacuum controlled. There is a servo/actuator under hood with a cable going doing to axle disconnect. Vacuum actuator is controlled by a vacuum switch near firewall on driver side under hood. Check for missing, broken or cracked vacuum lines. BTW, there is not "hub" to engage, it just couples and uncouples passenger side axle shaft from diff.  

on an 03 s10 ZR2 pick up? obviously I don't know for sure on the 03, I can find one to look at when I get to minneapolis tomorrow, the older ones are vacuum for sure as snoman described, If the shop changed the actuator it would have had a cable control on it for the vacuum diaphram. they would have been able to see it working on the firewall, fender or where ever it is, which would have told them if it has a vacuum problem. I'd like to belive they would have checked for a vacuum problem before changing the actuator asembly if it is in fact vacuum controlled. if we didn't call it a hub, no would know what we were talking about, basicly it is a hub. what is the technical name for our so called hub?  

It is a "axle shaft disconnecter" or "central disconnect"  A hub is assumed to be out by wheel. GM disconnects on shaft and lets other spin out in spider gears and then drive shaft and ring gears does not move/spin in 2wd. Dodge is the only Detroit SUV maker (Jeeps too) that does not disconnect front axle in 2wd (only drive power to it) so the drive shaft and gears are always driven by wheels which is not doing your MPG any favors. BTW, that model year has a vacuum powered disconnecter. Only full sized models have a electrical servo driven one.  

thank you, now I wonder if the manual posi locker will work on that thing?  

mudb8-.:
thank you, now I wonder if the manual posi locker will work on that thing?

The diff or the axle disconnect? If you are talking about disconnect the answer is yes. It would be possible.  

haha getting too technical for me guess that's why i'm not working on it huh?  i'm now beginning to wonder if the mechanic has any idea at all what he's doing and he's just acting like he knows what he's doing to rack up a big labor bill and then never get it fixed.  It will be two weeks this next tuesday.  

awe, just keep in touch with him I'm sure it'll end up fair.  two weeks is a while, maybe poke him a little,  

well he found out what it was I HOPE anyways he says for sure this time supposed to get it done today.  I really don't know what the part is called it's kinda like a differential in the front end that the actuator cable runs down to that synchronizes the gears or something in that nature too much mechanic talk for me haha, but anyways he took the drain plug out of it and it was like a 90 weight gear oil in it and he showed it to us it was half oil and half metal the oil was just shiny and silver.  gonna cost us $250 but hopefully that fixes it.  also there is a cv and a boot that is bad and spraying and shooting oil all over the underneath and he said those usually ran around $60 but since he had the truck for so long he was gonna take care of that for us.  Shheewww I hope this fixed it time.