Hello i am new here so i hope i am at right spot but my 2005 blazer just the other night roads got bad i put it in 4wheel dr and dam neer went off the road it was real squirly in 4 wheel drive and fine when i put it back in 2wheel drive anybody ever had that problem

 

Welcome!

With our Blazers, there are two common issues with our 4wd systems; the transfer case control module (TCCM) and the vacuum lines that do the engagement of the front axle and depending on the system, also the transfer-case.

If you are not getting any funny blinking on the 4wd selection buttons when you try to engage the 4wd system and you don't get any series of clicking coming from the TCCM (which lives behind the passenger side kick-panel), then a likely culprit is vacuum leaking in the vacuum lines. When the TCCM is failing, you can hear the relays clicking on and off several times trying to set the circuits and then giving up.

What often, but does not always, also occurs with a vacuum leak to the 4wd system is that the actuators for the HVAC system that direct the air to the different outlets will also not work correctly. This is because both use vacuum supplied from the engine to work.

If you have a "4-button" 4wd system (one with a 4th button for Auto 4wd) then a link I have in my signature below will be of use to you for checking and replacing the vacuum lines. If you have a 3-button system then the link is still useful but not quite as much as the transfer-case on these is also controlled by a vacuum switch on the transfer case. (On the 4-button systems, the transfer case is controlled electronically.)

There are other things that can go wrong on the transfer case but I'm not so familiar with that.

Hope this helps.