Engine/Transmission (1994 - 1998) 4wd Light Blinking

[ProMac1K]

I've had my 4wd dash light on for several days and finally got time to work with it today. I was assuming the hubs were staying engaged, as when the transfer case is shifted, the truck is in 4wd right away as opposed to earlier when it would take some throttle or movement. I crawled under the truck and wiggled some vacuum lines, and removed/installed the lines that connect to the vacuum mechanism on the front axle. After that, I started the truck up and the light went out after seconds. All was fine until I got up to 15 mph, then the light started progressively blinking at an increasing pace as I increased speed, until it finally just stayed on. And then it goes out when under 5 mph. Also, it doesn't always come on at 15 mph, just depends how you're driving. I was sliding back in forth in the snow on the gravel road with the front wheels turnng back and forth, and the light never went on.



Anyone ever seen this? All the vacuum lines are intact and plugged in. The light progressively blinking would make me believe that the hubs were progressively engaging, that's my only thought. Any ideas?

 

[ProMac1K]

Pretty discussing group here I see..... LOL

 

[MrDiesel]

Did you try to un-plug the vacuum to make sure it won't engage, then drive it to see if the light stays out?

 

[RDelissen]

it's definitely got to do with the vac lines ... same stuff happened to me a couple of times and every time there was a loose vac line

 

[ProMac1K]

I'll try that tomorrow.



Thanks!

 

[ProMac1K]

it's definitely got to do with the vac lines ... same stuff happened to me a couple of times and every time there was a loose vac line

Yeah, I was having some issues earlier. I ended up pulling the vacuum boot/plug off the t-case, putting it back on, and then I ziptied it, and it worked.



What makes me wonder is why it blinks progessively with the speed. Makes me think that either something is trying to engage, or else the switch sensor is bad.

 

[DieselDoghouse]

Sounds familiar—for me at least it meant a new vacuum motor for the front axle. If they wear out and get weaker apparently getting on/off the throttle and the resulting driveline torque will 'shuttle' the motor shaft and the light will flicker on/off. I say this based on replacing the switch (no change) rechecking vacuum lines (no change) replacing the #@^ motor at $200. 00+ (problem solved) a new motor will have the vacuum pull to keep the slide yoke and the motor shaft butted firmly against the switch - no flickering. Plan on needing a new motor every 4+ years if you're someplace like NE.