Trimatic Correcting Overfilling

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Page created by T Jan 30th 2017:

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V8 Trimatic. Item 2 is the Modulator. Click to Enlargen. Photo by Hot308VK.

Trimatic Correcting Overfilling:

Trimatic Normal Operating Oil Level Readings:

A Trimatic gearbox's Normal Operating Oil Level can only be accurately measured when the engine is hot and running and the vehicle is stopped and standing on level ground.

Dipstick Reading Details:

Use a reading from the Dipstick to work out how much ATF to drain from the Trimatic. (from the low to the full Hot Mark is 0.5 Litres).

A Drain tray with graduations can be used to measure the amount removed.

Bleeding the Radiator Lines:

Safety First: Keep hands and fingers clear of the moving fan if using this method.:

The easiest way to lower the Trimatic Fluid Level is by loosening one of the Trimatic Lines at the Radiator creating a small controlled leak (about 2mm wide). Any thicker might mean fluid loss to the internals and result in damage. A slow leak allows ample time to respond to the drop in fluid. By measuring the amount drained from the Trimatic the Dipstick level can be corrected. The leak will only appear while the engine is running.

A 1/2" AF pipe Spanner (to loosen and retighten the pipe) and a 9/16" AF pipe Spanner (to hold the adaptor) are the best tools for the job.

Removing The Modulator:

Removing the Modulator is another way of draining out excessive ATF if the Trimatic has been overfilled. Take a reading from the Dipstick to work out how much ATF to drain (from the low to the full Mark is 0.5 Litres). Place a Drain Can with graduations on it under the Modulator then remove the Modulator from the Trimatic. When the excess amount appears in the drain Can, refit the Modulator .Recheck the Oil Level after correcting the overfilling.


7AT15 Spanner for bolting/unbolting the Modulator.
The 7AT15 Modulator Spanner. It is 1 1/4" AF and 3.0 mm thick. Click to Enlargen, Photo by T.

Removing The Vacuum Pipe:

Remove the Metal Hose from the rear of the Modulator by twisting and levering off the rubber connection with a screwdriver.

Removing the Modulator:

A special thin Spanner 7AT15 is used to remove or replace the Modualtor because the space between the Modulator and the Trimatic Case is small. The Modulator Spanner is 1 1/4" AF and 3 mm thick. Unbolt the Modulator by turning it anti-clockwise with the Spanner.ATF will pour from the Trimatic when the Modulator is removed so use a Drain Tray of some sort to catch this Oil.

Replacing the Modulator:

Fit the paper Gasket to the Modulator and place the Pushrod into the end of the Modulator.Screw the Modulator into the Trimatic Casing finger tight. Tighten the Modulator using the 7AT15 Spanner. 

Replacing The Vacuum Pipe:

Refit the Vacuum Pipe as per the image on this page. Pull the rubber connector back along the Vacuum Pipe.Plug the metal Vacuum Pipe into the Modulator.Twist the Rubber along the Vacuum Pipe until it sits half on the Modulator Pipe and half on the Vacuum Pipe as in the Image. Note that rubber can become hard and brittle with age and need replacing.




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