4 Wheel Drive

[jeremystoddard]

My 4 wheel drive well not operate correctly. No matter which 4WD button i push the light just blinks unless i go back to 2 high. The switch is clicking and the transfer case sounds like it is switching but nothing else happens. I have seen all of the vacuum problems but i'm not sure mine has the vacuum system. There is a line running off of the front Diff but i traced it to under the air filter and it is not hooked up to anything. This problem just started and the 4 WD has not been used since last winter. So it hasn't been used for about 6 months. Any help would be greatly appreciated.

[vballfun]

I have a 95 blazer that I have had the same problem with at least 3 times over the past 3 years.. I would push the 4 hi button and it clicks and sounds like it's going to engage.. but it just sits there and blinks.. (and if I recall correctly it went back by itself to 2 hi after about 15 seconds)

wasn't crucial to have 4wd at time so I ignored it. However I had to change my alternator like a few weeks after it happend the first time (unrelated) and in the process of disconnecting the battery and reconnecting it.. the next day the 4wd switch was working... since then I've run into the problem 2 more times.. and just 'guessing' i disconnected the battery for a minute and reconnected it. So I'm guessing maybe something computer related was keeping it from engaging for some reason and reseting the power cleared the memory??

anyway.. i know it's not an 'answer' but it may be a quick fix.. however if it is the computer not letting us switch I would like to know why it would not let us switch to 4 hi.

[jeremystoddard]

I will definetly try unplugging the battery. I have tried almost everything else. I have checked the fluid in the transfer case, front differential, and tranny fluid. Everything is good. I would still like to know what that hose from the differential to under the air filter is because there is a connector there also that is not being used. I have been in the haynes repair manual. Which does no good because it talks about the older transfer cases and differentials but just mentions the newer ones. I had heard that they went electric control instead of vacuum for the newer models but i don't know how true this is. Thank you for your reply and if i find out for sure what it is i will post it.

[Lola Run]

I had the same problem. In the end it seems that the transfer case control module was damaged due to moisture. One thousand dollars later it works perfectly, even better than before. You can pick up your own TCCM and install it yourself. What I can tell you is not to play with the buttons, i did and it got stuck in 4wd. Making it very difficult to park in a space without making a three point turn. The Haynes manual will tell you how to change the TCCM.

[Lola Run]

Maybe I post a picture of the damage to the TCCM. Which was minimal, two corroded connectors. But it seemed to have shorted out the push button controller aswell.

[vballfun]

Originally Posted by Lola Run

Maybe I post a picture of the damage to the TCCM. Which was minimal, two corroded connectors. But it seemed to have shorted out the push button controller aswell.

Hmm that could be what is wrong with mine.. As I've noticed electrical problems with the push button control box...I've replaced the little light bulbs in the 2wd and 4lo twice over the past 4 years... (but never had any problems with any other dash lights) and the 2wd light seems noticably dimmer (by about half) than the 4hi and 4lo lights and you can see it sort of 'flicker' so maybe there is a short in there somwhere...