Four wheel drive won't work

[Man In Black]

I just bought a 93 GMC K2500 4X4 pickup with a 5 speed standard trans and was told when I bought it that the 4 wheel drive light didn't work but the 4 wheel drive does , but in fact it does not. I found the fuse and it is good and I know there is a sensor on the front axle tube and it looks like another one on the transfer case. Could someone tell me what each of these sensors do and could either one be my problem. The four wheel drive does not work in either 4 high or 4 low.

 

[Z15]

Well know design flaw in 88 to about 97 GM trucks....

Early 90's trucks used a gas operated actuator to engage the front axle. Its located on the right hand side on top of axle tube and has a wire connector on it. These were prone to loosing effectiveness and taking a long time to engage 4x4 or out right failure when the gas in the cylinder became inert. GM came up with an electrically operated actuator that required a new wire harness and some modifications. Its been so long since I had one of these trucks I don't recall all the detail. You might be wise to talk with a local GM dealer you trust for his opinion on this. 99 times out of 100 the front axle actuator is the problem.

 

[Man In Black]

Well know design flaw in 88 to about 97 GM trucks....

Early 90's trucks used a gas operated actuator to engage the front axle. Its located on the right hand side on top of axle tube and has a wire connector on it. These were prone to loosing effectiveness and taking a long time to engage 4x4 or out right failure when the gas in the cylinder became inert. GM came up with an electrically operated actuator that required a new wire harness and some modifications. Its been so long since I had one of these trucks I don't recall all the detail. You might be wise to talk with a local GM dealer you trust for his opinion on this. 99 times out of 100 the front axle actuator is the problem.

Thanks, from what I have been reading since I posted this I am leaning toward changing this actuator. Does the auto parts store handle these new conversion updated parts instead of having to pay GM's prices ? Also are there any other switches or sensors on the transfer case that should be changed? I don't have any indicator lights.

 

[Molson02536]

I just bought a 93 GMC K2500 4X4 pickup with a 5 speed standard trans and was told when I bought it that the 4 wheel drive light didn't work but the 4 wheel drive does , but in fact it does not. I found the fuse and it is good and I know there is a sensor on the front axle tube and it looks like another one on the transfer case. Could someone tell me what each of these sensors do and could either one be my problem. The four wheel drive does not work in either 4 high or 4 low.

This link should help you get your 4wheek drive issue addressed.

Good luck and be safe.
http://gmcowners.com/gmc-forum/showthread.php?t=16687

 

[Man In Black]

4 wheel drive won't work

Thanks Molson, This is what I was looking for so I can get an understanding of what parts are involved and where the wires are coming from and going to. I can also feel some wires going to some kind of a switch right above the actuator on the axle tube. What is this and what function does it have? This truck will just be used off road for a crane truck and the 4 wheel drive will just be locked in and never come out, is there any way to eliminate the cost of the actuator and just somehow make something to push the pin in and hold it . I assume that you only need the actuator if you want to change from 2 to 4 wheel drive and vice versa. Thanks again for the help.