Hello all, I just bought a 99 blazer.. 2 dr 4wd. I found shortly after I bought it that the 4x4 is not functioning. I am sure you have answered this question before, and i searched and found part of my answers I hope.

Heres what happens.

1. driving in 2hi is fine. When I push the 4hi button, the 4hi light blinks, but never goes solid.
2. I cannot hear and kind of actuator or solenoid activating.
3. 4lo does something... the light still just flashes and does not stay solid. However when I drive it feels as though is it slipping in and out.

While crawling under my truck I discovered a 5/8 (I think it was 5/8 it was pretty big) vacuum line that was rubbing on the exhaust and is completely melted off. I figure this is the problem (I am guessing anyway) however, for the life of me I cannot find where the other end of this vacuum line should go. It comes out the driver side of the transfer case, snakes over the transmission and that is where it is melted, just before the y pipe on the exhaust.

The other thing, I cannt find this vacuum ball that I have read about in other posts... Where is it located under the hood? Is there any vacuum lines going behind the glovebox related to the 4x4 system?

Thank you so much for your help, I am new here and appreciate you helping the newbie

Thanks!

Bryce

 

Hello Newbie. Welcome

The vacuum line. There should be three of them coming off the t-case. One provides vacuum to the t-case, one takes that vacuum and provides it to the vacuum actuator (located under the battery tray) and one is a vent line for fresh air. It also ends by the battery. You know know where two of the hoses go to. The vacuum hose that provides vacuum to th t-case comes off a tee fitting located behind the distriburator cap on the passengers side. One side of the tee fitting goes to the vacuum ball. On my truck the bal is located on the drivers side near the headlight. The third side of the of the tee goes to the vacuum source off the intake manifoldnext to the distriburator cap in most cases. The vacuum lines also run into the cap of the truck typically through the firewall about in the middle and just below the hood. If oyu have a leak in any of those lines, you should have heat-a/c vent issues, and maybe performance issues.

The flashing light and back to 2hi indicates the t-case did not shift into gear. To get into 4hi you need to be going less then 40mph, it varies, but that is a good guidline. To get into 4lo you need to have the tranny in nuetral and moving less then 5mph, or preferrable stopped. Same with getting out of those gears. Now if you violated those rules, the light will flash and go back to solid in 2hi. If you didn't violate those rules, post up.

Hope that helps! [8D]

 

wow, thanks for the fast reply... I am going to go have a look now but its raining outside

I am definitely not breaking the rules of shifting However you said the flashing light on 4hi then back to 2hi, when I push the button for 4hi, the 4hi light flashes and keeps flashing, It doesnt go back to a 2hi light, just keeps on going... unless it takes more then 3 minutes to switch back, I have never waited that long.

Im going to check the vacuum lines as soon as the rain stops.

Thanks again, I will get back to you soon.

Bryce

 

Your welcome.

I have never heard of it continually flashing like that. Normally if it isn't going to shift into gear it will flash a few times and go back to the previous selection. That sounds like a new problem. Although it could be related to a lack of vacuum line feeding the t-case.

 

well I went and had a look. First off, I could only find the one vacuum line on the tcase, nor could i find anywhere else that a vacuum line would go. The only vacuum line I can find on the tcase is the one I was saying that was melted from rubbing on the exhaust (it was 5/16 not 5/8 haha) I pulled the battery out and had a look at the actuator below the battery. If I hit the 4hi switch, nothering happens there... the vacuum line that goes to the actuator actually comes off one of the lines from the "t" that is by the distibutor. On the way there it goes through some kind of switch or sensor or someething mounted to the firewall. The other end of the T dissapears into the firewall on the driver side (to work the vents perhaps?) I looked and looked and cannot even find a ball anywhere. This seems odd.

Does it make a difference that my model has the auto 4wd as well? does that change the way the vacuum lines operate?