I have searched through the net(including this forum) and have seen quite a few issues similar to mine and several possible solutions.


My question is more what is the "danger" possibility if I don't get this fixed right away.


My issue is I can start the blazer, switch between any of the 4x4 modes at will, and the all engage. As soon as I start moving the blazer, give it maybe 20 seconds, the service 4x4 comes on and I cannot take it out of the mode it was put in unless I restart the truck. The 4x4 works just fine though, I just can't switch the mode after that service light comes on.


What is my danger level if I use the 4x4, mainly 4high, while the light is on?

 

If you have the 3 button switch on the dash, do not operate in 4HI or 4LO on dry pavement. If you have the 4 button switch on the dash, you can operate it on dry pavement in AUTO or 2HI only.

Is the ABS light on?

 

No abs light, only the 4x4 service light.


4 button dash switch, auto..2wheel, 4high, 4low.


We got a snow storm here so I have been driving it in 4high, and its worked fine except for not being able to change it to another mode until truck restart.


Didn't want to trust the auto mode if its having problems as I wasn't sure it could even switch on its own if it detected slippage, so I just put it in 4high.


My main concern is if it could do any damage doing this.

 

The only risk of damage would be when operating on dry pavement while in 4HI or 4LO. Could do some serious damage to the transfer case and or differential(s). Using a high end scan tool capable of accessing the TCCM, (Transfer Case Control Module) would reveal the problem.

 

Probably stupid question but how does the system know if it is on dry or snow packed road for whether damage can occur?


Thanks for the help, hopefully I can get it in soon to be looked at.

 

It's not a stupid question. It's a question that you want to know the answer to, and that's good

When in 4HI or 4LO there is a direct mechanical connection between both differentials. On dry pavement, if for some reason one differential loses traction, something has to "give", and it's usually the transfer case chain. And yes, it's an expensive noise

When you select AUTO, the rear differential remains powered and the front differential is locked, but not powered by the transfer case, (no mechanical connection between the differentials). If/when the TCCM detects slippage from the rear differential, it commands the encoder motor on the transfer case to apply power to the front differential incrementally, until there is no slip, or a 50/50 split of power, (front to rear) has occured. This is done through a clutch pack inside the transfer case.

 

You will have to forgive my ignorance as I just bought the blazer yesterday.


So you are saying the auto mode behaves differently than 4hi?


Is it as effective as 4hi?


I was testing yesterday on a snowy hill to make sure 4 wheel was still working when the error was being displayed.


In auto, when I threw the peddle down the blazer was acting like it was still in 2 wheel, fish tailing around, didn't really seem to me that the front wheels where engaging.


When I tried the exact same thing in 4hi it tore up the hill without any fish tailing.


Is the auto just less effective... or am I right to assume that due to whatever issue is going on, if I put it in auto its never going to engage the front?

 

AUTO does behave differently than 4HI, (as described in post #6). When it's working properly, the transition from 2HI to 4HI is nearly seamless. It was designed for those "I don't know if I need 4WD or not." road conditions It detects when you need it and automatically engages 4WD. If you leave it in AUTO all the time, fuel mileage will suffer and a certain amount of unnecessary wear on system components will also occur.

If it was fish tailing in AUTO, and not in 4HI, it probably was not engaging 4WD in the AUTO mode. And yes, you are correct to assume that due to whatever issue is going on, if you put it in auto its never going to engage the front... until the issue is repaired.

 

Thanks for all the info, you have been a great help.


Where I live I suspect most of the snow to be melted in a few days off the road again and at that time ill switch back to 2 wheel.


Hope to be able to get the issue fixed soon but good to know it won't hurt anything if I start the blazer, set it in 4hi and then when the error light comes on just drive it that way(so long as there is snow).

 

I'm sure you're not alone with this problem. Keep us posted.