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Joined: Jul 2005
Posts: 88
Shade Tree Mechanic
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OP
Shade Tree Mechanic
Joined: Jul 2005
Posts: 88 |
Greetings All: I am attempting to adjust my vacuum shift mechanism on my '48 Cabriolet and can't get it right. The car shifts fine with no vacuum hose attached, but when I attach vacuum the piston extends and the shift selector lever goes up, as if toward rev or second. I tried running the adjusted screw in and out and the failure mode is always the same. Sometimes I can just get it to hold in N and I can hear the valve hiss, but in no time - boom it's back w/ the handle up. I do have a problem w/ the threads on the adjuster screw that prevent me from adjusting to the full forward. Does this sound like a sticky valve, or maybe it's working as expected and is just still out of proper adjustment?? HELP!!
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Joined: May 2002
Posts: 3,578
ChatMaster - 3,000
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ChatMaster - 3,000
Joined: May 2002
Posts: 3,578 |
Are you using the adjustment guage for the cylinder?chef- 
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Joined: Jul 2005
Posts: 88
Shade Tree Mechanic
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OP
Shade Tree Mechanic
Joined: Jul 2005
Posts: 88 |
Well, I did fab the gauge as the manual describes, but as soon as the engine applies vacuum the piston extends forward in car, loading against the linkage / fingers. The manual suggestes that the valve should move with little trouble - it shows a pix of a hand pulling / pushing on it. Mine is not free to move like that, so I can't effectively use the gauge (yet). Because the valve doesn't move freely like the picture suggests, and the failure is always the same (as I described), I suspect it's stuck, but it does go to N sometimes and I can hear it venting (HISS). I soaked it in WD40 last night. Maybe things will go better tonight. I would pull the can from the car but the Cabriolet frame really boxes it in tight.
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Joined: May 2002
Posts: 3,578
ChatMaster - 3,000
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ChatMaster - 3,000
Joined: May 2002
Posts: 3,578 |
If it were me I would certainly concider having the vac cylinder rebiult...a very small investment for a very big inprovement,chef-
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Joined: Dec 2001
Posts: 10,379 Likes: 1
Technical Advisor ChatMaster - 10,000
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Technical Advisor ChatMaster - 10,000
Joined: Dec 2001
Posts: 10,379 Likes: 1 |
Don't give up on your project. When adjusted properly it is a dream to shift. If you do decide to yard it out and find you need parts or help, let me know. The adjusting gage is available from Chev's of the 40's or from me. 
RAY Chevradioman http://www.vccacolumbiariverregion.org/1925 Superior K Roadster 1928 Convertible, Sport, Cabriolet 1933 Eagle, Coupe 1941 Master Deluxe 5-Passenger Coupe 1950 Styleline Deluxe 4-Door Sedan 1950 Styleline Deluxe Convertible 2002 Pontiac, Montana, Passenger Van 2014 Impala, 4-Door Sedan, White Diamond, LTZ 2017 Silverado, Double Cab, Z71, 4X4, White, Standard Bed, LTZ If you need a shoulder to cry on, pull off to the side of the road. Death is the number 1 killer in the world.
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Joined: Mar 2003
Posts: 959
ChatMaster - 750
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ChatMaster - 750
Joined: Mar 2003
Posts: 959 |
After I got mine adjusted on my 40, it was a dream to shift! 
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Joined: Jun 2003
Posts: 437
Backyard Mechanic
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Backyard Mechanic
Joined: Jun 2003
Posts: 437 |
The vacuum hose should be very flexible for correct action...
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Joined: Jul 2005
Posts: 88
Shade Tree Mechanic
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OP
Shade Tree Mechanic
Joined: Jul 2005
Posts: 88 |
Thanks guys - - What a difference a day makes. As I mentioned, night before last I soaked the valve area w/ WD40. Last night I was able to free up the valve stroke and I can now see/understand how it works. I think I have it adjusted right now. It no longer fights me and DOES seem to offer lighter shift efforts. One more related question: I see the instructions for lubricating the unit, and what a pain that would be. As I said, on the Cabriolet that unit is not easily removed. Can I introduce some fogging oil or other lube at the vacuum intake with the can in the car rather than removing the unit??
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