I have had very few automatic transmissions in my lifetime, so I know less than I suppose I should. This one's a C-6. When I start the engine in the morning, shifter in the Park position, I often feel a very slight, very short tendency for the van to try to move forward. Why?

 

Hey seattle smitty,

Have you discussed this with your Ford Dealer? I recommend doing so. You may locate one (and schedule an appointment online, if needed) here.

What's the model, year, and current mileage of your ride?

Todd

 

No, no, this is an old beater, a 1988 e150, efi 4.9L that originally had an AOD, which some previous owner changed for the c-6.

 

That happens with some transmissions.


Nothing to be concerned about.


Fluid is a bit thicker and the convertor thinks it should be working.

 

Wait a minute, isn't the converter full of fluid and turning its output shaft all the time, running the pump all the time? If the valve body is in the Park configuration, why would there be any gears meshed to apply any torque to the driveshaft? Is the viscosity of the fluid such that it can actually impart a little torque to the transmission output shaft? If so, why is the effect I tried to describe only felt for a little less than one second? Or could this have anything to do with the bands or their adjustment (only one in a C-6)?? This probably sounds like I'm trying to argue with you, but I just need more explanation. If it's the converter, is this effect dependent on whether it's a lock-up type or conventional converter? (What I NEED to do is hunt for an animated drawing of an automatic transmission, and quit asking you to hold my hand! I'm nearly as old as you, Stuart, and should have taken more interest in automatics just as a matter of being mechanically-educated).

 

Ford Transmission Forum:


Yes the convertor is full of fluid and turns whenever the engine is running. There is an impeller inside that does not turn until engine RPM is increased. This impeller is connected to the input shaft which is splined to the forward clutch drum. The surge is only momentary. Next time start the vehicle in Neutral and see how far you get. The only time a transmission will drive for any distance in Neutral is if a clutch pack was seized. Which in your case is not because every other gear works. Above is a blow up of a C6 transmission.

https://www.google.ca/?gws_rd=cr&ei=...nverter+images

 

I'll look at it. Meanwhile, yeah, I wasn't thinking, the projection at the back of the converter housing is running the pump all the time, but the impeller isn't running short of whatever the stall speed is for the converter . . . right?

 

I'll take a look at your blow-up. Meanwhile, yeah, I wasn't thinking; the stub on the end of the converter housing is driving the pump all the time, but the impellor and it's shaft aren't doing much if anything below the stall-speed of the converter . . . right?

 

(EDIT) delete double-post

 

Something about this site has changed, gives me these problems, drives me nuts!

 

Yup. The pump turns when the engine turns. Sends fluid to various circuits. Convertor charge and lube being the primary points.

Like I mentioned fluid is a tad thicker on a cold start but thins out very quickly.

 

On a fact trip. At peak torque. When the transmission is in gear. One foot planted on the brake. The other on the gas pedal. The amount of fluid circulated in the convertor is equal to 45, 45 gallon barrels of fluid. 2025 gallons.

 

You forgot to say in what amount of time.

 

One minute.

 

What, maybe two or three gallons flowed at the rate of two thousand gallons in one minute???!!!!!! Seems physically impossible. No wonder there's a cooler!