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1972 Ford Five Hundred - We have a modulation problem here

I have a 73 ford 390 w 3speed c6 sucking quarts of trany fluid
And I am the only person who touches this vehicle. Bad (smashed) modulator is the problem.

Replace the modulator no more problem.


When you replace the transmission modulator, replace the rubber vacuum hoses. Transmission fluid will attack the rubber.

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Had that happen on our 1968 Olds. My mom replaced the modulator, my uncle was giving her instructions over the phone.

The only surprise to me here, if that is the original modulator, is that it has lasted almost half a century.
Rubber generally gives up way before then.


Well someone else must have touched the car to smash the modulator. It’s not in a place easily hit by road debris.

Short post and I completely forgot the smashed part. My bad. Someone would have to be pretty vindictive to try and slither under the car a bit to intentionally cause this damage. I would think a hammer would leave a distinctive mark unless this was one of those once in a million freak road debris events.

I did see an old Chevy come in once with a leaking power steering pump and someone had taken a small ball peen to it 3 or 4 times but the pump was pretty accessible on that car.
Can’t understand why someone would go after a difficult to access modulator when there are easier targets such as a screwdriver through the grill, condenser, and radiator or whatever.

Wow are you guys that thick headed?
Any number of objects on the road could have damaged the modulator.

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It would be very difficult for road debris to damage a modulator. Not impossible; just difficult. So what is the point of this exercise?

And transmission fluid from a damaged modulator is not going to end up in the oil. It will get burned and spit out the tailpipe as white smoke. And as far as I know any ATF is going to go through a vacuum nipple on the intake and not the carburetor.

My thick headedness is not my fault.When I was born I was a wee bit slippery and the doc dropped me on my head. The ensuing half dozen caroms of my skull on a tile floor left me intellectually shortchanged…


What’s so exciting about that? Replacing failed vacuum modulators was a routine repair when the cars that used them were still on the road. I still see one every now and then. It’s a cheap quick and easy repair.

And no, the trans fluid never made through the carb or into the oil. The vacuum line is routed to a port below the throttle plate and then directly into the cylinders.


No body ignored that the ATF was being burned, that is what happens when it is sucked into the combustion chambers.

My questions are. Did you do anything about it? Or, did you just come to to profess you mechanical prowess?

Gee Wiz i must be the lucky one.
Never in recorded history has trans fluid managed to saturate an area of a motor and found its way into the crankcase this is AMAIZING.
Oh by the way thick headedness is not caused by being droped! I should know each of my parents only had one arm which unfortunately resulted in many drops and my head is quite soft!