I've been having problems with my front axle since having my vacuum and steering pumps replaced. I notice a “popping” sensation at front wheels when holding steering wheel tight to right or left and moving slowly (going in/out of parking space). I’ve had the shop which performed the repairs check out the new steering pump and steering gear box, and they claim both are OK. I’ve changed both front U-Joints. Last night I found the vacuum line going to the front axle always has vacuum – regardless if the T-case is in 4H, 2H, N, or 4L. I installed a vacuum switch (~ 2 years ago) to shut off the vacuum to the front axle when I want to put the truck into “2-low” for maneuvering and/or backing up a trailer – I usually keep the switch off unless needed. By keeping the switch on while in 2H, my “popping” seems to stop. Why would my vacuum to the front axle be on all the time? Could the mechanic have crossed vacuum lines when he installed the new vacuum pump? Could the vacuum control switch on the T-case be failing? I’m suppose to leave for a 2-week trip to MT in the morning, and want to make sure I’m not risking serious damage to the T-case or front axle while off-road driving in the mountains.

Also (may be unrelated), I notice the “4WD” light on my dash is messed up – it comes on when I know the T-case is in 2H. It acts like there is a short in a wire: light comes on when going up hill, “flickers” while driving on flat roads, goes out while going down hill, hitting a pot hole, or stopping. The light is behind my steering-column-mounted trans temp gauge, so I didn’t notice when it started coming on (it is always off when I first start up the truck and look at my gauges). Where should I look for a loose or chaffed wire?

Thanks, Frank

 

There is always vacuum to one hose or the other at the axle. They should switch back and forth from 2wd to 4wd.

The 4wd light is activated by the axle locking collar that the vacuum actuator moves.
Unless the switch is failing or wires are shorting together when the light is on the front axle is locked.

Though not the best practice aside from faster tire wear I see no problem driving long distances in 4wd.

 

Thanks for the reply infidel. I'll take it easy on this trip and look into replacing the CAD with a manual switch when I get back...