I have 1984 Ford F250 with 6.9 diesel, C6 transmission.
Does c6 trans have torque converter? Just wondering because feels like kinda lock due to take off very quick from start, little pedal. Quicker than my friend 92 7.3 f250. His take off slow and smooth with little pedal, and mine take off quick like bang with pedal. So thats why I asked.
Or better torque converter than nowdays?

 

The C6, as nearly every auto trans, has a torque convertor. The diesel version is a lower stall RPM than a gas rig (excluding the 300 I6), to take better advantage of the low RPM torque of the engine.
That said, it's possible you could have an issue inside the TC or trans, if it isn't smoothly transitioning the power to the wheels.

 

Well its pulls good, smooth to wheel, I'm just curious why pulls quick in low rpm instead of high. Like when i do in little pedal goes 1400. moves pretty good, but my friend 92 goes 2100 rpm. Like when he move the gear selector to drive, truck doesn't move in idle maybe very little, give some gas, it moves.mine will roll very easy after put into drive, have to apply brake enough to stop moving. So means c6 torque converter work at low rpm than 90s? I like to learn about it.
Also, can you adjust the transmission not to shift late? Shift early? Because my truck built for pulling power, so I do slow driver, engines always revs high before shift. I want to shift early, for better fuel ecomony, more tq at low end than no power at high end. Do u know what I'm asking? I want learn all the stuff how things works.

 

Used to pull cattle trailer and now for daily driver.

 

The E4OD has a higher stall torque converter because it has lockup, the C6 does not so to work with the diesel's rather low rpm range and to keep rpms under control on the highway, it has a much lower stall.
Yes, the vacuum regulator valve on the side of the injection pump is adjustable, and that will modify the shift points, however, explaining how it works is better left to someone that has one rather than myself.

 

Thanks for a great info

Well what about the rod that's hook from throttle carb to transmission? Rod moves after pushing the throttle.

 

Not only can the vacuum regulator on the injection pump be adjusted, but most C6 tran modulator valves are also adjustable. Both can done to adjust the shift points of the trans. I recommend starting with one in the trans. Inside the vacuum hose there should be a small screw. Twisting this screw in, should delay the shifts, while turning it out allows for a lower RPM shift point.

As mentioned, the C6 diesel torque convertor is a much lower stall RPM, by design. It will cause the trans to pull a bit at idle speed. But, since it is pretty much at max engagement by 1400 RPM, it takes advantage of the torque output of the diesel, which also happens to be maxing out at around 1400 RPM.
The 300 I6 shares the same low RPM torque output, so the torque convertor is also designed in same fashion, for the same reason. You could say Ford "borrowed" the idea from the 300, since it came along well prior to the diesel. (nearly 20 years)
I'm not saying the 300 and diesel use the same convertor, (though they may) Just that they share the same style.