A904 not downshifting, dark film in bottom of pan

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briwill70

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Recently rebuilt trans and removed the pan to inspect the linkage movement. Car was also not downshifting when throttle is wide open but throttle kickdown is connected and appears to be working. Dark film at the bottom of the pan and I've only driven about 40 miles. Transmission was fried before rebuild so possible some of that material came from the torque converter. Thoughts? Other reasons why it will not downshift?

IMG_8543.jpg
 
Recently rebuilt trans and removed the pan to inspect the linkage movement. Car was also not downshifting when throttle is wide open but throttle kickdown is connected and appears to be working. Dark film at the bottom of the pan and I've only driven about 40 miles. Transmission was fried before rebuild so possible some of that material came from the torque converter. Thoughts? Other reasons why it will not downshift?

View attachment 1715529479

That film is actually normal because aluminum wears off the impeller and stator which shows as a dark film like that.
FYI, the converter should have been replaced when the trans was built.
You could be right about some of it coming out of the converter though, as when the converter spins centrifugal force throws junk to the outsides and it packs around the impeller blades and sticks in there.
Still some comes loose and you will see it in a new rebuild if running the used converter from a previous trans failure.

As far as kickdown goes, has it worked ok before?
It's pretty tricky to get a kickdown at slightly higher speeds, unless the trans has a part throttle kickdown.
Early trans didn't come with the part throttle kickdown and later ones did.

You could try giving a bit more on the TP by adjusting the linkage and see if it kicks down after that.

PT kickdown valve assembly looks like this.
The add on section is what is the PTKD is if you want to take a look for it.

s-l1600.jpg
 
I adjusted the linkage and got a tiny bit more travel from the kickdown. It appears to be all the way now a WOT. Will try it out when it stops raining.
 
That film is actually normal because aluminum wears off the impeller and stator which shows as a dark film like that.
FYI, the converter should have been replaced when the trans was built.
You could be right about some of it coming out of the converter though, as when the converter spins centrifugal force throws junk to the outsides and it packs around the impeller blades and sticks in there.
Still some comes loose and you will see it in a new rebuild if running the used converter from a previous trans failure.

As far as kickdown goes, has it worked ok before?
It's pretty tricky to get a kickdown at slightly higher speeds, unless the trans has a part throttle kickdown.
Early trans didn't come with the part throttle kickdown and later ones did.

View attachment 1715529485
I know I should have replaced the converter but I'm only planning to drive around this summer while I build another engine/trans combo.
Not sure if the kickdown ever worked before. This thing sat for 20 years with a burned up trans from a kickdown lever breakage. Rebuilt the clutch packs and valve body and put it back together.
 
If the trans isn't too fried, i don't recommend replacing the converter; especially on a 727, but those 904 converters are prone to cracking by the slots.
 
Have you changed the rear gear from that which your trans was originally married to? or
Did you crank up the line-pressure?
Either of these may require a different governor assembly.
 
I know I should have replaced the converter but I'm only planning to drive around this summer while I build another engine/trans combo.
Not sure if the kickdown ever worked before. This thing sat for 20 years with a burned up trans from a kickdown lever breakage. Rebuilt the clutch packs and valve body and put it back together.

I really don't want to sound like a dick here, because I don't know how else to say this but now you are paying the price.
That said, I can't really say that I wouldn't have done the same thing actually. (and I could have paid the price.) :D

But lets concentrate on where to go from here.
What I would do, and of course this is just another A hole's opinion is to start with some TP adjustments and see if I could get in range to kickdown.
What could be happening in your case is that the contaminants from the converter could have gotten into your valve body and governor and is sticking things up causing the governor valve not to be able to move freely enough to let it kickdown.
It also possible your internal pressures are off enough to cause it, in which case you may want to put a gauge on it and test them.
Then there's the part where your trans may not have the part throttle kickdown assembly on it. (those work great for kickdown mid throttle under high load conditions, which works about perfect for a street car.)

If the pressures are in the range they should be you might just slap a new filter on it and drive it.
Or you could just put it all back together right now, fill it up with fluid see what happens.

See, it ain't all bad.
You at least have choices.:D
 
I really don't want to sound like a dick here, because I don't know how else to say this but now you are paying the price.
That said, I can't really say that I wouldn't have done the same thing actually. (and I could have paid the price.) :D

But lets concentrate on where to go from here.
What I would do, and of course this is just another A hole's opinion is to start with some TP adjustments and see if I could get in range to kickdown.
What could be happening in your case is that the contaminants from the converter could have gotten into your valve body and governor and is sticking things up causing the governor valve not to be able to move freely enough to let it kickdown.
It also possible your internal pressures are off enough to cause it, in which case you may want to put a gauge on it and test them.
Then there's the part where your trans may not have the part throttle kickdown assembly on it. (those work great for kickdown mid throttle under high load conditions, which works about perfect for a street car.)

If the pressures are in the range they should be you might just slap a new filter on it and drive it.
Or you could just put it all back together right now, fill it up with fluid see what happens.

See, it ain't all bad.
You at least have choices.:D


I know I probably shouldn't have cut corners but my impatience and thriftiness got the best of me. I put it all back together and drove it a couple miles. Adjusted the kickdown so it is fully depressed at WOT. Shifts are now later and firmer but does not kickdown at any speed. Otherwise works normally.
 
That film is actually normal because aluminum wears off the impeller and stator which shows as a dark film like that.
FYI, the converter should have been replaced when the trans was built.
You could be right about some of it coming out of the converter though, as when the converter spins centrifugal force throws junk to the outsides and it packs around the impeller blades and sticks in there.
Still some comes loose and you will see it in a new rebuild if running the used converter from a previous trans failure.

As far as kickdown goes, has it worked ok before?
It's pretty tricky to get a kickdown at slightly higher speeds, unless the trans has a part throttle kickdown.
Early trans didn't come with the part throttle kickdown and later ones did.

You could try giving a bit more on the TP by adjusting the linkage and see if it kicks down after that.

PT kickdown valve assembly looks like this.
The add on section is what is the PTKD is if you want to take a look for it.

View attachment 1715529485
Here's a picture of the valve body when I had it apart. Looks at though it may not have the PTKD?

IMG_8421.jpg
 
Nope, and those are not real easy to find either.
Maybe just live with manual downshifts only with it till you get your other setup ready, since it sounds like it's working ok.
 
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