Thread: Turbo 400 problem

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Any transmission guru's out there. I am new to this as far as posting info so hope this is coorect way. I have a turbo 400 in my Henry J that now does not want to shift until I hit very high RPM, near 6,000. Prior it functioned normally, with a manual/auto setup. Does not seem to be slipping. Fluid level is good. I am wondering if the small piece on the side of the tranny that the vacuum line goes to has anything to do with the shifting? Should I change this out before going ahead and removing the tranny for service?

Thanks !!!

The piece you are describing is called a vacuum modulator. It is common for the rubber diaphram to get a leak in it. Change the modulator before yanking the trans...
Mark

Last time I had a busted modulator diaphram, when letting off the gas the vacuum would create lots of smoke (sucking up tranny fluid).

Maybe its a leak in the vacuum hose rather than the modulator its self.

Bert

sound like its staying in low gear. on a 400 if you put it in low gear and dont shift, it will shift at 6000 rpm by itself. if the modulator goes bad it still should up shift , late but not that late. be sure your passing gear sw. is not ingaged all of the time and be sure the gov. is working.

check the vac. at the modulator and modulator
unplug the kick down sw.
clean the gov. (be sure the piston is free)
clean the valve body

The kickdown switch could have come lose creating an internal leak. To check that you are gonna have to drop the pan. A no vacuum condition as well as a stuck governor or a broken governor gear could be at fault as well.