TH400

[bd]

When you change the fluid, take an inventory of anything you find in the pan (ie, steel, brass, aluminum, rubber, or flakes of paper).

[cliffnuce]

So I readjusted the TV cable and when I started the truck and moved the shifter to reverse it moved forward. When I put it back in park it still moved forward. It is stuck in forward gear. New Transmission?

[bd]

...It is stuck in forward gear.  New Transmission?

Maybe.  But first I would drop the pan and...

...take an inventory of anything you find in the pan (ie, steel, brass, aluminum, rubber, or flakes of paper).

Depending on what you find in the pan, you may have your answer.  Also, take a look at the manual valve and make sure it is connected and moving in direct conjunction with the external shift linkage (no play).

...if your linkage is working properly then you may have a stuck valve in the valve body.

It doesn't cost anything to look.  Best of luck.

[cliffnuce]

So I finally got to look at this thing again today. I dropped the pan. There was no debris other than the normal sludge. So I changed the filter. Cheked and everything seems to be moving correctly.

So here is what it does.

In park with the engine off it is in park. With the engine running it moves forward. I put the shift lever through all gears and it still tries to move forward.

With the engine off it seems to go through the gears ok even though you really can't tell.

What next??      

[bd]

You may have a forward clutch that isn't releasing.  The forward clutch should be applied in all forward gears, but never in park/neutral/reverse.  This 'could' be caused by a stuck 1-2 accumulator valve in the valve body.  To clean the valves and valve body, the valve body needs to be removed from the trans case and totally disassembled.  I recommend that you don't even consider doing this yourself unless you have the appropriate ATSG or similar manual.  When you lower the valve body, you'll be uncaging a few check balls that will seem to come to life and roll in all directions, some escaping to the far corners of the universe.      ...well, maybe not quite that far!      But, you have reached a decision point....