4 low

Hey guys,
A newbie to the forum here. I just bought a 1997 Z71 ext. cab. I need some transfer case advice. My 4 low is not engaging. The light just blinks. I think the front axle is engaging b/c you can feel the difference the steering in 4 hi. (i.e. the tight steering effect of the 4 wheel drive). 4 low feels the same I don’t think the trans case is changing ratios.
Any advice?

And when I start it up in the morning the first 25 feet the truck rolls I feel some kind of metal grinding noise from the front of the truck(it will only do it if it is rolling). Kind of like bad breaks(metal on metal) it only last a second. And the lights (dash & headlight) usually dim(weird???). It will not do it again until I let the truck sit for probably 4 hours.

Anyway you may think that I bought a pile but the truck is in relatively good shape the engine/trans are strong. And the exterior/interior is clean. I plan on rebuilding the front end and I fell it will be a really good truck. I would appreciate any advice with my dilemmas.

Thanks in advance!!!
Richard

Do you have manual hubs on the front?

So 4 hi does work? That is interresting...I'll have to think a little about it. Maybe someone else can help.

Thanks for the reply goinbig.

I am assuming they are auto, whatever is stock. I don’t think it has been modified.
It doesn’t have the manual locking hubs that you have to get out and lock.

Thanks,
Richard

I think this weekend I am going to jack it up and put it in 4 hi and see if all wheels are turning. The 4 hi light comes on and locks in but the 4 low light just blinks for a while. And then returns to 4 hi ( I realize the potential to be on Americas funniest home videos attempting this so I will have the wife ready with the video camera!!!!!)
Anyway, hypothetical situation here. If I got the truck and didn’t know a lot about push button 4x4’s and I tried to engage 4 low in drive would that mess it up?

When you jack up the vehicle, make sure that all 4 tires are completely off the ground and that no one is standing too close to the vehicle.

Where you moving when you put it in 4 low? If so, how fast were you going?

4 Lo should only be engaged in neutral and at a stop. That would be in the owner's manual but seeing as you bought the truck used, you probably don't have it.

I was at a full stop and in drive with my foot on the break. I hit the button and all the 4 low light did was blink.
later I found out that this wasn't the correct way. I think doing that somehow messed up the transfer case solenoid or something. How does the transfer case work does it always stay engaged and just switch from high to low?
If so I can see how my truck could still work in 4 hi and not 4 low.

Richard

The manual suggests that you be moving less than 5mph and in neurtral. I get the most painless(quietest) shifts just barely rolling in neutral. If you are not in neutral the electronic transfer case will not shift to 4-lo. Be careful with it up on the jacks if you still have to do that.
Jeb

P.S. - oh yeah, when driving it on pavement in 4wd you are going to get some pretty nasty sounds if you turn any(especially in low), so I'd just drive straight or test it on a real loose surface.

What might be happening is that it shifts into 4 hi check to see if you can reach the same speed in 4lo in 1st and you will know whether or not its engaged

I am almost positive 4 hi is working.
and I am pretty sure the front axle is engaged.
but since the 4 low light is blinking and retuning to 4 hi I am thinking that the transfer case solenoid is not functioning properly.
I am going to use 6 jackstands to lift it up and I am not going to rev it up like an idiot. I just want to see all 4 wheels turning in 4 hi that way I know that at least that is working....
and definitely won't be crawling under it and ending up on faces of death!!!!!
in first gear it will reach the same speed while the light is blinking. I am almost positive that the transfer case is not shifting. is there a way to test the solenoid?

I have the 98 K1500 and it's the same set up. It's like TXAGG05 & Mikado14 said, you must be in neutral. try pressing the button several times. And also try going from 2wd to 4 low. Mine hangs up sometimes, but i'm always able to get to engage with a little persistence. And try this too, holding the 4lo button down for a couple seconds before releasing. What did you pay for this truck? and how many miles on it?

Some times with the pushbutton you just have to play with it for a little while try rolling forwards and back at a very very slow speed and the gears will line up the actuator cant push them in umless its perfect

Ok… I am positive 4 hi works…
I took a quick look at the transfercase to see which solenoid controls the shift to 4 low. I see plenty of connections. Which one is the solenoid that shifts to 4low? I want to test the wires to see if it is getting power. If it is getting power then I may need to remove it and check actual solenoid…

Thanks guys I am getting close on this I think. I hope it is a solenoid of wiring problem and not the trans case….

Ok… I am positive 4 hi works…
I took a quick look at the transfercase to see which solenoid controls the shift to 4 low. I see plenty of connections. Which one is the solenoid that shifts to 4low? I want to test the wires to see if it is getting power. If it is getting power then I may need to remove it and check actual solenoid…

Thanks guys I am getting close on this I think. I hope it is a solenoid of wiring problem and not the trans case….


DrkGrn/wht (dark green with a white stripe) is your 4Lo from selector switch to your transfer case control module.

thanks skipr,
"case control module"?
were is that?
is it the big solinoid on the bottom front of the case?

thanks skipr,
"case control module"?
were is that?
is it the big solinoid on the bottom front of the case?

No thats the actcuator , it's under the IP(interior fuse panel), on steering column support bracket.

OK let me get this strait. I need to test @ the module "dark green with white stripe wire" for 12 volts.
If I have 12 volts then move on to the transfer case actuator.
Do you think the module is bad? or the switch?
The 4 low light is blinking....
Thanks for the help.

OK let me get this strait. I need to test @ the module "dark green with white stripe wire" for 12 volts.
If I have 12 volts then move on to the transfer case actuator.
Do you think the module is bad? or the switch?
The 4 low light is blinking....
Thanks for the help.

Going through the control module makes it so you can't just swich the diff. anytime you want. Must be in neutral for 4 lo to engage. So if you send the signal to the Contol Module the control module will check the trans input to see if it's ok to send to the actuator.

Well I pulled it all apart and I dropped the Control Module. I tried to find the wire but in a color blind state with a flashlight. It wasn’t possible. Well when I put it all back together it started working. (go figure) Anyway it is real loud when it shifts in to low. Is that normal or should I be a little weary about the transfercase. The uv joints seem to look good the rear ones are new. It couldn’t hurt to change the front ones.

Well I pulled it all apart and I dropped the Control Module. I tried to find the wire but in a color blind state with a flashlight. It wasn’t possible. Well when I put it all back together it started working. (go figure) Anyway it is real loud when it shifts in to low. Is that normal or should I be a little weary about the transfercase. The uv joints seem to look good the rear ones are new. It couldn’t hurt to change the front ones.


It,s normal to make a loud clunk when the front diff. locks into place. It shouldn't clunk again untill you unlock the diff.

My 2000 Silverado had the transfer case gears go bad and had to replace the whole thing at about 90,000 miles even though I only used 4WD twice since I had it...bought used. After the dealer replaced the transfer case I went on a trip and had occasion to use 4WD...it would not shift out of 4 low no matter what I did. I took it to the local dealer and they fooled with it for about an hour and it finally worked...they did nothing to it. Today I had the truck in for servicing at a transmission rebuilder I trust and had them check it out. They said everything was ok...but they mentioned that they have replaced many many of the dashboard 4WD switches and they are notorious for going bad...so...maby your messing around with the thing helped it somehow and it now works...for a while. There is also info I read in their shop while waiting for their servicing that was good..."Transmission Digest" June 2004 issue, page 58-59 about the Silverado NV246 transfer case with a common occurrence having the transfer case shifting disabled and the SERVICE 4WD indicator lamp illuminated. The problem is where the ATC fuse is open and goes open as soon as you turn the key on. In each case the location of the power short has been the same. "When you follow the bulk wiring harness from the ATC motor/encoder, you will note that it runs along the top of the frame between the frame rail and the cab body. When the harness nears the steel frame body support, it begins to make an upward turn toward the PDC and bulkhead. Right at this turn the harness is quite taut. The plastic conduit spreads open at this point and esposes the wiring harness with it rubbing against the steel frame body support and chafes the wires. To do the repair you have to remove the shorted section and solder a length of wire as there is very little wire there originally . Then heat shrink wrappit and use good grade electreical tape to keep it closed. This may not relate to your problem directly but remains a possibility to look at.

My 2000 Silverado had the transfer case gears go bad and had to replace the whole thing at about 90,000 miles even though I only used 4WD twice since I had it...bought used. After the dealer replaced the transfer case I went on a trip and had occasion to use 4WD...it would not shift out of 4 low no matter what I did. I took it to the local dealer and they fooled with it for about an hour and it finally worked...they did nothing to it. Today I had the truck in for servicing at a transmission rebuilder I trust and had them check it out. They said everything was ok...but they mentioned that they have replaced many many of the dashboard 4WD switches and they are notorious for going bad...so...maby your messing around with the thing helped it somehow and it now works...for a while. There is also info I read in their shop while waiting for their servicing that was good..."Transmission Digest" June 2004 issue, page 58-59 about the Silverado NV246 transfer case with a common occurrence having the transfer case shifting disabled and the SERVICE 4WD indicator lamp illuminated. The problem is where the ATC fuse is open and goes open as soon as you turn the key on. In each case the location of the power short has been the same. "When you follow the bulk wiring harness from the ATC motor/encoder, you will note that it runs along the top of the frame between the frame rail and the cab body. When the harness nears the steel frame body support, it begins to make an upward turn toward the PDC and bulkhead. Right at this turn the harness is quite taut. The plastic conduit spreads open at this point and esposes the wiring harness with it rubbing against the steel frame body support and chafes the wires. To do the repair you have to remove the shorted section and solder a length of wire as there is very little wire there originally . Then heat shrink wrappit and use good grade electreical tape to keep it closed. This may not relate to your problem directly but remains a possibility to look at.

When he says "use good quality elect. tape" use Super 33+ by 3M

Good info guys. 4 low is still working. But try this one on for size. I have to mess with it for usually 2 min. before it finally engages. I have read about the brown wire bypass (recall) on the board. I see a wire by my transfer case that looks like what has been described. Do you guys think that there could be a short or loss of connection in the bypass? After if finally engages it usually goes in and out on demand.

Thanks,
Richard

Sorry I can not help more. I use my 4WD so seldom...4 times in 4 years..but...mine does seem to be touchy. The guy at the transmission shop told me that there is a safety control in the computer that prevents it from engaging if the vehicle is moving over 3 mph. He said it absolutely must be in neutral the best results for switching in and out are obtained with the truck just "barely" moving with the explanation that just like any transmission the gears must mesh and the very slight movement helps to prevent the teeth from jamming during switching. Your problem may be electrical though from your description. I do not know of a good way to test the dash panel switch but replacing it might be good to do. Since it does work I have some doubts about wiring being the problem ...but that kind of thing can sure be tricky.