4 wheel drive doesnt work......

[Chvytruck95]

When i bought my 88 4x4 i had to immediatly rebuild the engine so i didnt try out the 4 wheel drive, well i finally got it running and everything and took it out in my pasture....i noticed that when i got stuck in a mud hole in 4 hi the front wheel were not turning at all only the back wheels, so i put it in 4 lo, with the same result, so i jacked it up and put it on blocks and put the truck in 4 wheel loo and hi and the front tires didnt spin at all, i looked under it and saw that the front driveshaft was turning but nothing was happening, nothing looked unplugged,does it need fluid in the front differential??? i dont know much about how four wheel drive works so i need some help here what could be the problem????

[jveik]

do you have manually locking hubs? if so, you must engage them or else the wheels will not be given any power. there should be a little dial or whatever on the center hub of each front wheel. im assuming you know this though so sorry if im stating the obvious

[Wheeler88]

Check the shifter linkage if it's OK then it's probably the thermal actuator that has failed. Also do a keyword search on the word "actuator" in this forum for a wealth of info.
Here's a site that sells an aftermarket workaround that is more reliable then using the OEM actuator.
http://www.4x4posi-lok.com/app_chevy-k.html

[Chvytruck95]

here is a little bit more information, i know that the linkage to the transfer case is okay cause when i put it in four wheel the gears are lower like it is in 4 wheel but the front tires just dont move at all its just like there are no gears in the front differential or something.......

[goinbig]

So does it have manual locking hubs??

[67malibu]

The thermal actuator on my '88 K1500 began working sporadically several years ago before failing to engage at all. I replaced it with a Rancho unit and haven't had trouble since. The stock unit takes six to seven seconds to engage, the Rancho takes about one second.

[Chvytruck95]

Okay so where exactly is the thermal actuator? no it doesnt have manual locking hubs..........

[67malibu]

Originally Posted by Chvytruck95

Okay so where exactly is the thermal actuator? no it doesnt have manual locking hubs..........

It's been six to seven years and I don't pay much attention to the actuator whenever I'm under the truck so bear with me if my description is a bit off. From underneath the truck, look at the side of the front differential facing the passenger side. You should see a cylinder-looking piece running out from the differential parallel to the axle. It will be about the size and shape of one of those energy drink cans (maybe a bit bigger) with a wiring harness coming out of it. It's pretty easy to change, I think it only had two bolts holding it in. One word of advice if you do change it: if the new unit doesn't appear to work at first give it a few tries. My new one didn't appear to engage with the first couple of tries but then started and has continued to work flawlessly. I think it had to adjust itself. The Rancho unit is mechanical, not thermal as the stock unit. The stock units first started failing in extreme cold weather because the actuator would get too cold from packed on ice.