904 giving up the ghost?

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MopaR&D

MopaR&D

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So I was driving my Duster home from work today and the transmission started slipping, like it would go out of gear when off the throttle then when I'd get back on it it would go back into gear. It was pretty much all freeway but once I got into my neighborhood it started slipping really badly and I was babying it back to my house. Once in front of my house I immediately put it in Neutral and checked the fluid. The level was fine, perhaps a tad high actually but the fluid was still perfectly clear-pink and didn't smell burnt at all. So I put it in reverse and it didn't do anything; it would start moving slightly if I gave it a little gas so I was able to get it into the garage.

From talking to a friend who has experience rebuilding Torqueflites he thinks the line pressure is low. What would cause that to happen? Could the pump fail that quickly? I saw mentions of a bad seal that can cause the trans to lose pressure? It was quite hot outside today and this is the first time I drove my Duster in weather this warm since last summer, I read if the seal is on its way out the colder fluid will seal but when it warms up and thins out it won't seal anymore?

I'm kind of a newbie with Torqueflites, I understand how they work on a basic level but I've never been inside one other than to replace the filter or adjust the bands.
 
Check line pressure, there is a port on the side of the case. Report back...
 
Woods74 said:
Check line pressure, there is a port on the side of the case. Report back...
Click to expand...

Ok, I don't have any of the stuff to measure it though... guessing I need to go buy a gauge with a line that has a 1/8" NPT fitting on the end? Not sure where to get that either, Harbor Freight? I've never had to buy a pressure gauge before, aside from my compression tester which came in a kit.
 
Alright cool, I'll stop by there on my way home from work tomorrow and pick up a gauge. Really hoping it's just a seal inside I can replace it would be nice to not have to drop the transmission.
 
Just to better prepare myself and have an understanding, if I was looking at a loss of pressure what would the next steps be?
 
I don't mean to be bumping this thread but I decided to wait on fixing my Duster's transmission until my truck is back on the road, or at least close to it (in the process of doing a 4-barrel conversion). I've been doing a ton of research in the meantime trying to get a better idea of what's going on and it's looking like I'll most likely need to drop the transmission; I still need to verify the hydraulic pressures but I tried driving it again the next day with everything cooled off and the symptoms seem to be pointing towards a pressure issue. If I put it in Reverse it seems to go into gear fairly normally although somewhat soft; any forward gears and nothing really happens, not the "thunk" like it's supposed to but if I give it some gas with the shifter in a forward gear it feels like it slips into gear and kind-of moves. I've also been thinking about how high the fluid level was on the dipstick; it was WAY above full, like 1" over and I know for sure it's not overfilled (topped it up last year to just below Full line with engine running in Neutral in my mostly-flat garage, also checked the fluid level when it started acting up with engine running in Neutral). That makes me think the fluid isn't being pumped properly and looking through my 1970 Plymouth FSM in order to fix that I need to get access to the front pump which would mean dropping the trans...??

I might do a hydraulic pressure test this weekend if I have some spare time but I don't want to start taking anything apart until I have all the necessary tools and a solid plan of what needs to be done. I want to minimize down-time for my Duster as much as possible because I'm trying to compete in time-attack events this summer and the first session is May 31st which I'll obviously have to miss but I really want to make the next one which I believe is mid-June. I also want to use this as an opportunity to wrap my head around how Torqueflites work in detail; reading text and looking at pictures only goes so far, I can't really understand how something works until I get my hands on it and take it apart myself.
 
Was just talking to a friend who mentioned the filter might have fallen off and I remembered I installed the deep pan and a filter extension when I put the trans in the car almost 10 years ago but never checked it since. Guess I'll do a pressure test tomorrow then drop the pan, I want to see how things are in there anyway after 10 years of hard use.
 
CudaFactHackJob said:
If you're sure that it has enough fluid in it....then it's toast.
Click to expand...

"Toast" to what degree? I have a hard time believing the entire transmission is junk...?

This is driving me nuts, still not quite done with my truck but screw it tomorrow morning I'm figuring out what the heck is going on here.
 
Automatics aren't designed to slip. When they do; they turn the friction discs to toast. Don't worry, we'll help you overhaul it.
 
CudaFactHackJob said:
Automatics aren't designed to slip. When they do; they turn the friction discs to toast. Don't worry, we'll help you overhaul it.
Click to expand...

Well that's the thing this started slipping so severely and so suddenly I wasn't able to drive it while it was slipping (and babied the heck out of it getting back home) so the clutches wouldn't get burned up. I just drained the fluid and it is CRYSTAL clear; looks and smells like I just poured it out of a brand-new bottle and this fluid is about 8-10 years old. Heck now I kind of wish I saved some of it to put back in that was like 6+ quarts but oh well, won't hurt to put fresh fluid in there.

I finally hooked up my gauge and did some pressure tests. The line pressure didn't move the gauge at all, I had the rear wheels off the ground so they could spin and I ran the engine with it in Drive and Low letting it shift up through the gears and such, nothing. Not even 10 psi, even manually working the throttle-pressure (kickdown) linkage which my FSM says should increase line pressure as it approaches the WOT end had no affect at all. So I hooked the gauge to the rear servo which my FSM says should show 230-300 psi in Reverse; well I got a staggering 30 psi from that. Went up slightly when I increased the engine RPMs but still barely over 40 psi, nowhere near 230. So I drained the fluid and I'm going to drop the pan today. After I go grocery shopping for the family... ugh lol
 
Ok, just got the pan off... looks pretty clean? Not much material in there compared to others i've seen

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Guess i'll pull the filter and extension too
 
Alright I went to remove the filter and the screws were loose! Not loose as in about to fall out but barely much more than finger-tight; took no effort with my screwdriver to take them out. I'm thinking this might be my issue?? The gasket that goes between the filter extension and valve body looks like it wasn't compressed fully around the pickup hole... kinda hard to see in the pic but I think there should be more pronounced ridges around the sealing edges, looks like it was never tightened quite enough.

15903771802716145374742504449264.jpg
 
Another pic without the flash... the screw that went through the hole on the far left was the most loose and you can kind of see in the gasket.

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EDIT: Thinking about it more though the fluid level was really high when I checked it I don't think it would have been able to suck air? And wouldn't it have made noises if the pump was pulling air?
 
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So... any thoughts on what I should do? At this point I'm going to put the pan back on with a new filter and fluid, make sure everything is tight and see what happens... if it's still not working I guess I gotta pull the trans and take out the front pump?
 
Even if the filter and extension weren't even installed, it wouldn't make a difference. If you are sure it was to the full mark....Drop the valve body and let's check out the pressure regulator valve or converter valve to make sure they're not sticking.
 
CudaFactHackJob said:
Even if the filter and extension weren't even installed, it wouldn't make a difference. If you are sure it was to the full mark....Drop the valve body and let's check out the pressure regulator valve or converter valve to make sure they're not sticking.
Click to expand...

Good to know I started thinking the same thing, the fluid level was well above the bottom of the throttle body anyway (at least 1/2" ABOVE the full mark) so like you say it shouldn't have made a difference.

I'll pull the valve body tonight or tomorrow, I spent most of the day working on my truck and it's finally back on the road so that's one less thing I need to worry about.
 
WOW, looks like I found the problem (huge crack!), guess I'll be needing a new valve body? Man I was not expecting to see that!

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Dang bro, you lucked out! Anybody ever seen that before?? You might take it apart and see if anybody has a spare upper casting laying around..If you're not in a hurry..it doesn't look like anything special.
 
CudaFactHackJob said:
Dang bro, you lucked out! Anybody ever seen that before?? You might take it apart and see if anybody has a spare upper casting laying around..If you're not in a hurry..it doesn't look like anything special.
Click to expand...

I posted a Wanted ad yesterday and got some replies already, I don't mind spending a little extra for the whole thing just to speed up the process a bit. I'll still be taking both apart and transferring over all the shift kit parts from this VB but I am trying to fix this sooner than later so I can be ready for the next track event in a few weeks.

That brings up the question of how exactly to do that and how do I identify what type of shift kit my current valve body has? If it's more appropriate I'll just start a new thread about it. I got offered a VB from a late 70s 904 and one thing I'm curious about is the part-throttle KD, my current VB doesn't have that feature and I don't know how it works?
 
CudaFactHackJob said:
Post pics of both sides.
Click to expand...

You mean both sides of the valve body?

I got my "new" valve body from a fellow FABO member @Jimacuda yesterday so I'll be working on that today. It's a stock one from a late 70s non-lock-up 904 so I'm interested to see how it'll be different? This transmission and valve body are supposedly 1966 units IIRC what the seller told me 10 years ago when I bought the trans lol.
 
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