Originally Posted by Mike B
bcgmc,

The valve on the transmission was the vacuum 2-speed rear control valve. The valve had a push/pull cable that went up to the gear shift knob for high/low selection. The vacuum lines attached to the valve went to the rear (Hi & Lo), vacuum supply up to the fire wall and a small line up to the speedometer adaptor. Do you still have a 2-speed rear?

The steel vacuum lines on the fire wall looks like it could be the fresh air filter for the Hydrovac. Is it attached to what looks like a valve cover breather cap mounted inside the cab?

The other lines on the fire wall are the vacuum lines, check valves to prevent backfires from blowing the vacuum lines up etc. You could have a large vacuum tank mounted on the frame as well.

The large cannister on the frame is most likely the original Hydrovac (brake booster) that was abandoned when they install the modern dual pot MC with it's booster attached.

Hope this helps,

Mike B smile



Yes I do but it has an electric hi\low shift motor. Can I take this valve off, is there any gasket from the valve to the transmission or is it just mounted there?

Yes there is a roughly 6" round canister mounted under the dash. It goes to the far pipe on the left on the firewall.

Yes I have a big tank mounted on the frame. About the size of a 5 gallon bucket.


Ok you say "abandoned" so I can remove all of this stuff including the original hydrovac tank? From looking at the pics of my MC can you confirm that it is a dual pot MC and that is a modern brake booster? Did the factory MC not have any type booster mounted directly to it? In other words the MC mounted directly to the frame?

Thanks Mike. Yes big help...