1999 Yukon 4x4 problems

[Shawn Speck]

Hello All,

 

my ‘99 Yukon won’t shift into 4 Lo. The front actuator is stuck fully extended. So it’s engaged (new on on order). The selector switch was not lightning up, so I removed it and cleaned up the connectors. It now works and can hear the motor working, but will only work for 2 hi and 4 hi. Is the problem with a still faulty selector switch, a fault signal coming from the stuck front actuator, or is the unit on the T-case bad?

 

thanks

 

[davester]

Front actuator is run off the TC, so it's not the problem (but I would still figure out why it's staying on, as it puts more wear on the diff with it engaged).

 

It could be any of the other things you wrote, or there could be a problem in the TC itself.

[Shawn Speck]

Thanks Davester,

the front actuator failed to retract even after being removed and disconnected. So, going to replace it. Like you said, excessive wear and lower gas mileage when left engaged.

The switch in the cab is being fussy. So, replacing it as well.

I guess if I still can’t get into 4-Lo, I can pull the TC motor and get a wrench on the shaft to see if it’ll shift into low, correct?

the trucks been sitting for about 5 years and prior to that didn’t use the 4 wheel drive for a few years.

 

thanks

[davester]

That sounds like a good idea.

 

I'm not sure if the actuator automatically retracts on it's own when not under power.  I think it needs power both ways, and it's my understanding that it's basically controlled by a switch in the TC (so when the TC is switched into a 4wd mode, it's powered to extend, and when switched into 2wd mode, it's powered to retract).

[Shawn Speck]

I pulled the actuator, still connected to the harness, and had a friend switch from 4HI to 2HI. It stayed extended. I could move it by hand, so it’s not jammed. Considering  the age of the truck, it’s cheap insurance to replace it. Amazon has them for $42, new replacement harness for $50, and the push button controller for $42. Ordered all three.

When I got the existing switch to work, the lights constantly flashed when 4HI or 4LO was selected and was solid in 2HI. I’m hoping that with the new switch I’ll get 4LO back.

 

I’ll keep you posted