So we rebuilt the 904 in my Dart a few months ago, and finally ran the car in another LeMons race in Colorado last weekend. Unfortunately, we had to shift with the 2 and D buttons all race because we could not get the kickdown to behave properly. Or is it fortunately? It actually worked surprisingly well and didn't break all weekend. And we won our class race, which is awesome. I'll link to the full race write-up by Judge Phil once it's been posted.

But anyway, I would like to get the thing to behave properly when you just leave it in Drive. Currently, it will shift from 1 to 2 at about 20 mph, with very little variation based on throttle input OR kickdown lever adjustment. This is too slow, in my opinion- maybe 2000 RPM in 1st. Depending on where you set the kickdown adjustment, it will either stay in 2nd way too long (and possibly never upshift unless you let off the throttle), or it will upshift into 3rd and never downshift again unless you come to a stop. At its current setting, it will actually do both: It will stay in 2nd forever with the throttle pressed to the floor, but once in 3rd, it will never downshift again.

This is very different from its behavior prior to the rebuild, wherein the upshift and downshift points were fairly close no matter the throttle position. The only gripe I had with it before is that I couldn't get the shift points high enough even with the lever fully actuated. Now it seems I have the opposite problem, but only on the upshift. It also seems like the shift behavior will sometimes change from one drive to another. Maybe it's dependent on temperature.

All this taken together makes me wonder if there's maybe a clog in the valve body. The behavior doesn't seem 100% reproducible, so that might suggest some debris that's moving around, or maybe something in the governor assembly is hanging up. We didn't touch any of this during the rebuild, and my understanding of how it works is not very good either.

A guy posted the following comments on our LeMons team Facebook page: "Did you use the factory service manual? They're very well written. You can run an oil pressure gauge temporarily to the test ports on the side of the trans and compare what you get to the chart in the manual. Try the governor port first. All those spools need sharp edges. Rounding them off with sand paper, or getting nicks in them when rebuilding could cause erratic behavior...
With the oil pressure gauge hooked up to the governor port, you should see it steadily increase as vehicle speed increases, and decrease with speed. When hooked up to the throttle pressure port, you should see it steadily increase and decrease with throttle movement. You may be able to do this manually by moving the linkage back and forth in drive and idling with the brakes on. Could narrow it down to valve body or governor."

Any thoughts? We'd like to get this operating well before our next race. Shifting with the buttons worked fine in Colorado, but I'm paranoid that pushbutton mechanism is going to break with all the abuse.

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Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
Escape Velocity Racing

Oh, is that why I saw so much "typewriter" action in the video!
Sounds like problems with the governor and/or kickdown band.
If you didn't touch it, you probably didn't clean it (right?). "Remove, disassemble, clean, reassemble, reinstall" is part of a rebuild.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

May I ask what year transmission you are dealing with ?

It's a 1964. Cable-driven, push-button A904.

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Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
Escape Velocity Racing

Not saying that this has anything to help you,,,The early torqueflite did not have part throttle kickdown so your 64 904 will only kickdown under full throttle and only if it can overcome the govenor pressure. I too had a 64 and if you are rolling at 20-ish mph it would not kickdown on it's own,had to push the buttons.Now I do know that the shops such as A&A Transmission and Cope Racing that specialise in Torqueflites have many different govenors that come in at different rpm.Again just a thought.
As far as the buttons,if your mechanism is clean and lubed,along with having good cables that are in adjustment I don't think you will break anything.They made them pretty tough back then.Sure sounds like fun,I'm jealous.

I believe Pat Blais has the parts to add part-throttle kickdown to the early cable shifted 904 valve bodies.

Conversations about part-throttle kickdown are far off target. He's not driving to the grocery for a carton of ice cream, he's racing, and his transmission isn't lacking a feature, it's broken.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

http://www.imperialclub.com/Repair/Lit/Master/index.htm Theres a book and film there.1964 torqueflte hydralics.

Sounds like a sticky governor to me.

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"A mechanic is Somebody."
- Jim Preston

I assumed this trans did have part-throttle kickdown, because (at least prior to the rebuild) it would downshift under part throttle at lower speeds. It's possible the previous owner added those parts, or maybe it was added when I had the trans rebuilt back in 2005. If I recall correctly, they had to transplant the guts from my original transmission into a new case, so god knows what else is different.

It sounds like I'll be dropping the pan at the very least to do some cleaning, so how can I tell for sure if my 904 has the modifications for part-throttle kickdown?

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Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
Escape Velocity Racing

What is this part throttle you speak of??

I would guess it does not have part throttle and you don't need it. I agree with Dan that is beside the point here. You have something stuck in the governor or TB.

Lou

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Home of Slant6-powered fun machines since 1988

Adding PTK to a pre-'66 transmission is not trivial. It can't be done by accident or by happenstance of using different-than-original parts. And it's still nothing to do with what you're experiencing.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I know it's a side issue, I just want to understand what I have so I know what it's supposed to do when I'm adjusting it later. It sounds like my understanding of this system has been wrong from the beginning.

I am planning to dig into the transmission and see what's stuck. I just need to wait until my teammates have recovered enough to even think about working on a car again. We get pretty burnt out after a race.

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Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
Escape Velocity Racing

Any updates to your issue? It sounds very similar to what my 83 b250 is doing. Thanks for your time.

To answer the above question, I haven't torn into this transmission yet. That being said, while idly researching transmission stuff related to my OTHER '64 Dart's troubles, I may have found a hint.

This thread by SlantSixDan describes the process for adding an in-pan transmission filter to pre-1964 cars, which didn't have one. In it, he notes that you need a 1964-65 filter with two fluid ports, one of which feeds the rear pump. 1966+ filters apparently only have one port.

Well... being idiot road racer types, when we installed this transmission after the rebuild, we went and added that Mopar Performance Deep Pan that Dan specifically warns someone not to use in that very same thread. If you look closely at the picture, you'll see that the extension does in fact have only one hole in it. So we apparently starved the rear fluid pump for an entire 14-hour road race. And a test session. And a little bit of freeway driving. :facepalm:



If you look at the diagrams in the '64 FSM, you see that the rear pump is active in all forward gears. It appears to *directly* feed the governor valve. You can probably see where I'm going with this.

Does anyone know if there is an aftermarket filter extension with two ports? Surely someone has put a deep pan on a pre-66 904 before. If not, and if I can't figure out a good way to modify this one, then I guess the original pan is going back on.

What are the chances of my rear pump being utterly smoked? In the worst case, I'm pretty sure I can get the tailshaft housing off without completely dropping the transmission out of the car, so there's that.

_________________
Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
Escape Velocity Racing