4000 S-O-S oddities

When the selector is quickly moved from 1,2,3,R1,R2 to Park, the pressure at the Servo 2 test port holds, and only very slowly drops to zero. Even if the power is cut. Once power is cut, the selector has no effect. Park applies after a very long delay.

If the selector is moved from Neutral to Park, the Servo 2 pressure drops quickly, and the servo 3 pressure eases down in a few seconds, engaging Park. If the power is cut with the selctor in Neutral, Park applies fairly quickly.

The service manual claims that Neutral is engaged by oil pressure applied to Servo 2. When I found that Neutral had full pressure on both servo 2 and 3, I looked at the control valve and found the cam applies both servo 2 and 3. All gears work, and the cams match the book otherwise.

Dave

I checked the other control valve I have, and it seems to have the cams set up differently - Servo #3 wouldn't get oil pressure in Neutral, making Park slow from any of the lower gears.

If it turns out to be that the Servo #2 oil bleed path is just too slow there may be a way to adjust it- but care / comprimise would be needed to avoid dropping into Park during shifts between 4th and 5th / 5th and 4th.

Dave

Off the subject a bit, manuals contain mistakes. I&T FO-20 is all screwed up. The 'Pressure Gage (sic) Readings' chart shows 180 psi to Servo 3 in R2, which is impossible. If the C carrier isn't held by B3, power can't be transmitted in a reverse direction. The 'Trouble Shooting Chart' uses one asterik to show spring-applied units (B2 and B3), and two asteriks to show pressure applied units (B1 and the clutches): The chart and the chart instructions contradict each other. I've also found at least one mistake in the SOS section of the Ford manual. Makes it interesting for the amateur. Pressure at Servos 2 and 3 in Neutral is a real puzzle. Some will think this is ridiculous, but I believe a cam was installed wrong at the factory. After all, with B2 and B3 released, the transmission does actually go to Neutral. In a discussion a while back, the man had two SOS tractors and could look at both control valves side by side. I don't remember any details, but it had to do with Nine and Ten, and the cams were different.

Well, I've made a long-winded post and provided absolutely no help. Is your transmission still on the test stand?

I was aware of the 4-5 shift timing to avoid park situation. I'm not sure if the slow park application was a side effect of that system, or intentional to avoid shock loads on the drive train. Perhaps the cam that applies pressure to both servo 2&3 was a later modification to make the thing more "driveable"?

I will look at the control cams from the spare transmission to see what they do in Neutral also.

Dave