722.1 control rod questions - PeachParts Mercedes-Benz Forum

Derrickd95 · #1 12-10-2017, 12:31 PM

Ok so here are my questions that hopefully help more than just me.

1. Making the control rod shorter produces more modulator pressure?

2. Mine is shortened all the way and I have no 3rd gear to really speak of, it's shifts way to soon and I have to manually go from S to D to have third gear.

3. Which nut do I remove to adjust the screwdriver adjustment to increase pressure?

4. Does more pressure stop flairs between shifts?

5. What's happening when I have my foot on the accelerator and the engine rpms increase but the transmission doesn't catch up? Does it need more pressure or is it because the trans shifted too early and the tranny doesn't have the pressure in the converter to push?

Frank Reiner · #2 12-10-2017, 12:59 PM

Quote:

Originally Posted by Derrickd95

Ok so here are my questions that hopefully help more than just me.

1. Making the control rod shorter produces more modulator pressure?
Although shortening the control pressure rod does have an incidental effect on modulator pressure, the primary effect of control pressure rod length is on shift points.

2. Mine is shortened all the way and I have no 3rd gear to really speak of, it's shifts way to soon and I have to manually go from S to D to have third gear.
The 722.1xx is a 4-speed transmission that normally starts in 2nd; 1st can be forced by either manually selecting "L", or by the kick-down switch under the throttle pedal. Your statement above suggests that you think the trans is a 3-speed.

3. Which nut do I remove to adjust the screwdriver adjustment to increase pressure?
If an original style vacuum modulator is installed, the banjo bolt that secures the vacuum line to the modulator must be removed to gain access to the screw.

4. Does more pressure stop flairs between shifts?
It often does.

5. What's happening when I have my foot on the accelerator and the engine rpms increase but the transmission doesn't catch up? Does it need more pressure or is it because the trans shifted too early and the tranny doesn't have the pressure in the converter to push?

What model/year vehicle is under discussion?

Derrickd95 · #3 12-10-2017, 01:40 PM

1976 w115 300d with a 4 speed

Derrickd95 · #4 12-10-2017, 01:42 PM

This transmission does not have any vacuum lines attached. That's why I was asking about the screwdriver adjustment of the modulator

Frank Reiner · #5 12-10-2017, 02:30 PM

Quote:

Originally Posted by Derrickd95

This transmission does not have any vacuum lines attached. That's why I was asking about the screwdriver adjustment of the modulator

The device installed in place of a modulator is a plug with a spring inside. the cap of the plug can be removed to gain access to a screw that adjusts the spring force.
The plug is located on the right side of the tail housing, just aft of the main case.