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Today, I got in my truck after not using it for about 1 week and needed to air up about 3lbs., which is normal, but when I went to turn the selector to both it was very heavy and hard to turn.
The manual CTIS directional valve is prone to get a bit corroded and grungy......on my first Hummer, a '95, mine got exceedingly difficult to turn and eventually began to leak.
It was a simple job to clean and repair......see the photos and description at:
I'm assuming you have a 94/95 truck with the manual selector... These CTIS selector switches are supplied without lubrication on the O-rings--I figure they're installed at the factory "as is" (no lubrication). I've had similar binding problems when the selector wasn't operated for a long time...
Recently I rebuilt my switch and applied a Teflon grease to the O-rings. I believe you can find spray Teflon (O-ring friendly) lubricants available, you might be able to spray in around the switch shaft and get some lube into the first O-ring... The selector switch knob is attached with two tiny set screws (Allen head), if you remove the knob you may have better success lubricating the shaft...
OK, now I'm interested. But, before I tear into mine, is there any chance this could cause a leak only in the rear tires and not the front? I can find no line leaks but when the rear CTIS valves are engaged, one or both, selector on vehicle on any setting, the rear tires leak. If set to all front tires leak also.
Next question, do I remove from inside or under truck? Mine is a '93 wagon.
If I understand your symptoms correctly it could well be your selector valve... Try applying modest sideways pressure to the selector knob and listen for air escaping... Also you might be able to push the knob in and get it to stop. If the selector is the problem then you can rebuild or replace it (although if replacing, I'd just swap the inner parts and leave the housing attached--too many angles on the fittings--too little clearance)... The switch is removed from the underside (this is a non-trivial job), and employs the usual frustrating locking nuts (free spinning--gotta be held from both sides). Also you'll probably need to remove your oil filter to do the job, so change to oil while you're in there... Anyway I'd say just yank the selector guts, if they look good, just go buy some O-rings... Else call Lynch the switch is about $28.00...
CTIS Selector Switch - AMG 06000031 (Valve, Selector, CTI - Parker-Hanifin)
BTW, I didn't realize CTIS was available in '93...
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