Hello my fellow Cat lovers, I have a question about my 69 transmission shift points. Was out for a ride the other day and my cougar now is running much higher Rpms before it will shift in to the next gear. Goes from first to second around 40-45 mph and from 2nd in to drive over 60 mph. It never used to do this. Is there a spring or vacuum line that might have come off? Maybe the linkage needs to be adjusted? Any help is appreciated. Thnx
Just MY 2 cents. C6 in mine, instantly shifts into second, third about 35, but sooner, if I’m easy on the throttle input. But if I’m just going light to light. More often than not, I’m ALREADY in 3rd. Seems right to me. Mines all stock… Transmission wise.
No expert here, just input. All three Ford automatics (C4, FMX, C6) use vacuum modulators for shift timing. Prolonged pattern, delay in shift - may indicate a vacuum leak somewhere or an issue with vacuum generation; timing, intake/exhaust restriction….
Ford automatics use a vacuum modulator to sense load on the engine. High load / large throttle openings produce very low vacuum signals, which will cause the transmission to hold each gear longer. The same will be true if you have a leak in the vacuum line to the modulator - raised shift points, higher line pressure increasing shift firmness.
The vacuum is sourced generally from a fitting on the rear of the intake manifold, uses a short section of rubber vacuum line, then transitions to a steel tube that runs down to the rear of the transmission case, then another short section of vacuum line that connects to the modulator. C-4 and C-6 modulators are on the rear passenger side, FMX is on the rear driver’s side.
First step is to make sure the two vacuum hose connections are intact and supplying vacuum all the way down to the modulator. If those are good, then it could be the modulator. When they fail, they will usually leak fluid through the vacuum fitting and cause your engine to smoke.
You could also have a stuck kickdown linkage at the carburetor.
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Great info here. I’ll start poking around this weekend. Has been leaking tranny fluid. As always you guys have great insight into these problems! Thnx a bunch
Steve