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Vacuum line off Carburetor to Transmission? 63' Dynaflow 2 speed


Guest Riviera1963

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Guest Riviera1963

So there was a vacuum line off the carburetor that lead down back behind the firewall, unfortunately when I went to go take it wasn't connected to anything down below. My guess is that is would be a vacuum modulator for the transmission, but I cannot find any place where it would go on the transmission. Is it even supposed to be down there? I have it capped off at the carb end for now. I have a 2 speed dynaflow.

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So you didn't say where on the carburetor the line was ported. So I'm guessing that the line you're referring to is the one that's up close to the top on the rear of the passenger's side of the carburetor. So that's not a vacuum line; it's a fresh air inlet for the hot air choke. So it connects to a metal line that is attached to the bottom of the passenger's side exhaust manifold. So it creates a loop for fresh air to the choke tube running through the exhaust manifold. So the Dynaflow transmission in your '63 is not a two speed. So it's similar to what a CVT (constant velocity transmission) is in today's new cars. So the ONLY things that the chassis manual suggests for L is snow or sand - IF YOU'RE STUCK. So don't use it as a driving gear. So sit back let the torque converters do their thing starting with the car in D and feel how effortlessly the car goes from 0 to "hold on to your hat!" without a shift.

So the Dynaflow doesn't upshift so there's no vacuum modulator needed to hold the upshifts.

Ed

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Ed is right, the Dynaflow is a Continuously Variable Transmission. Instead of a fixed number of gears, you essentially have an infinite number. It all happens in the fancy torque converter. It is magic. Everyone who rides with me comments on how smooth it is. Buick was known for that. And then you have the "Switch Pitch" part of the torque converter when at Wide Open Throttle, for an even faster getaway.

My car never sees sand or snow to need Low gear. I occasionally use the Low position on the selector to drive up a steep ramp in a parking deck. I also use it to creep into my garage when parking, without having to touch the gas pedal. Why? I think it is a good idea to apply pressure to that part of the hydraulic system once in a while to work all those valves, linkages, and bands, and to get some fresh fluid into those seals. Hopefully that will prolong their life.

In general, the Dynaflow is very reliable, if you change the fluid often to keep it fresh. The Dynaflow generates a lot of heat and heat breaks down the ATF. Eventually heat and time will cause the internal seals to fail and you need to reseal it. The bands and clutches last forever because they are never engaged and released at speed, under load, like a shifting 3-speed tranny. They are engaged at idle RPM and stay there all the time while driving.

If you start out drag racing with a Dynaflow selector in Low and then push it up to Drive after you are flying down the road, you will over-pressure an internal seal and eventually blow it, resulting in the need to rebuild the transmission. The transmission was not designed to be operated that way. Like everything else from Detroit in that era, they built the Dynaflow tough and it can take some abuse, but eventually you will pay the price for your joy ride.

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