I was reading the problems Mr. Greig Tyrell in the May/June issue regarding dually valve extender problems. I too had problems with leaking screw-on valve extensions on my Class C rear duallys. After doing some research found a place in California selling what is called Dually Valve kits. These are installed by tire dealers to replace the existing valve stems which are also as hard as hell to reach just to check tire pressures. I’ve had them on now for 4 years with no problems. I had a local tires dealer in Newton Surrey install them and they had no problems, there are detailed instructions in the kit. I also have the Hawkshead tire pressure monitoring system on just my rear duallys because if the inner tire goes flat it’s sometimes hard to tell.
Hope this helps, Larry