Hello and welcome to JustAnswer!
Have you checked to make sure the fluid is full? Low fluid will definitely cause this loss of fluid prime problem you are having. If you haven't checked it, start the engine, van on level ground, and check the fluid. If its low, top it off with Mopar ATF+4 only, and see if the problem still happens. If its low, you may have cooler lines or a solenoid pack leaking.
If the fluid is full, or you have already checked it, let me know.
Ok great. I saw you already changed the fluid, but it doesn't take long for enough fluid to leak from a solenoid pack or line to cause this problem. A leaking cooler line in the winter can lose enough fluid in a couple weeks to be 2 quarts low and cause this exact problem.
If the fluid is full, you've got a leaking low/reverse piston. This is the holding clutch all the way at the back of the case. The piston doesn't got right into the case, its not precisely machined for that. There is a stamped steel retainer that the piston seals to that bolts into the case. Over time this retainer will warp a bit, and it allows fluid to drain back into the pan while the engine is off. This causes the torque converter and everything else to empty, and when you start it back up all that fluid has to redistribute. This was a pretty common thing to happen on the older ones.
There is now a redesigned piston/retainer package for both the low/reverse and the 2/4 clutches, both holding clutches that use a stamper retainer and a piston. The originals had lip seals on the pistons, which last longer by design. There were some problems at the plant, and the assemblers couldn't get the lip seals in without damaging them, giving alot of the early A604 (41TE) trans problems. The fix at that time was to use D ring seals on the pistons. They are easier to install, but they can't conform to the piston retianer like a lip seal can. the newest design pistons have gone back to the lip seals, and they're bonded permanently to the piston. They have worked out very well.
On the bright side, you won't need to replace your whole trans. I replace a transmission opposed to rebuilding them about 30 to 1. Almost all transmissions can be rebuilt, and it sounds like yours is a great candidate for it. You should need nothing more than a master overhaul kit and torque converter, possibly a pump if its worn badly. I'd recommend a dealer over a trans shop if you do have it rebuilt, you'll get all the updated parts put in it, and they'll be higher quality.
You don't really have to do anything to it though. As you've seen this problem only shows up cold, and once the trans warms up and fills itself, it goes away until its shut off for a while. If you're ok with letting it warm up in the morning, don't even bother spending the money. This shouldn't cause any more problems with the trans other than the delayed engagement.
Thanks for your speedy response. I like your recent answer. What is your explanation for this not occuring in warmer temperatures? Is it because the fluid is much more viscous and the torque converter and everything that has drained fills up much quicker because the fluid flows much more easily past the leaking seal?
Also, does this old baby have anything like a transmission code fault computer? I was wondering if this could also be caused by an intermittent electrical problem that only occurs in cold weather - being the age of chips and such that are so sensitive to temperature. This should up as code fault on the computer if there is one. What are your thoughts on that?
It shows up more in colder temperatures. Like you've said the fluid can move quicker. The fluid will warm up faster, the seals warm up faster. The colder these old seals are, the harder and less pliable they are, so they don't conform to the retainers as well.
Your trans is fully electrically controlled by a module. Its located on the firewall next to the two relays, over towards the right side. There should be a code set for this, a code 35, loss of prime. Its a strictly hydraulic code.
Your trans is fully electrically controlled, the module controls solenoids on the front of the trans, this applies most of the clutches. If there were an electrical problem with a solenoid, pressure switch, or a speed sensor, the controller picks this up and puts you in limp in. To do this it shuts off the relay that powers the shift solenoids. Some solenoids are normally applied, some normally vented. This means when they are turned off some of them will apply clutches, and some of them won't. When the relay is turned off to give you limp in, the low/reverse and 2/4 clutches both come on, normally applied soleniods. This locks you in second gear only.
So, there will probably be a loss of prime code, possibly codes that have to do with individual clutch circuits having loss of prime because the pressure switches aren't closing, but a true electrical problem will lock you in second gear and turn the engine light on.
Since you mentioned the age of the module, I will too! There have been many hardware and software improvements to the trans controllers over the years. If you do have the trans rebuilt, you might think about replacing the module too. You'll notice a difference in how nice its shifts with the newer software. I recently went through this on my own 1994 Intrepid. The transmissions and controllers are almost identical, I spent the extra $175 or so on a new controller when I was done.
Thanks again for your response.
So to sum up:
What you are saying is that it is probably not an electrical problem because an electrical problem would put the vehicle in 2nd gear and the engine light would come on. Is that correct?
Also if you are correct about the fluid draining past the seals then my understanding of what you are telling me is that this fault should show up as an error code 35 (loss of prime) on the electrical control module (which you described as being on the rhs of the van) which controls the trans. Is this also correct? Can I have the module checked for this code by a trans shop or dealer?
PS. I have used my ignition switch (by counting check engine light flashes) to obtain other codes for faults in the past. Is there a way you know of for me to obtain the code 35 by myself from the transmission electrical module?
You've got it all pretty much correct.
If there was any sort of electrical problem the trans should go into limp in, and the engine light should come on. Until codes are cleared or battery disconnected, it would not come back out of limp in.
Normally this will set the code 35, loss or prime, in the transmission controller. This is the module on the right side of the firewall. The controller will first set a code for the low/reverse pressure switch, then 2/4, then if it gets bad enough it will set the loss of prime. You may have a 35, or any combination of that and /or pressure switch codes. The trans controller talks through the data link connector under the dash. It takes a full capability scan tool to do this, a simple code reader won't talk to this body style van. A dealer or trans shop will definitely be able to read the codes.
The ignition switch code reading is nice in a lot of cases. The codes can mean a few different things alot of times. They roll alot of different codes into one number for a bunch of them. For instance code 43 can be a coil code, misfire, or internal engine controller problem. The worst part of it for me (a trans guy) here on JA, is the key cycling won't normally give you trans codes. Its pretty much dedicated to codes that are stored in the engine controller, the module mounted to the inside left front corner of the left fender, behind the battery. They didn't give any way to get codes directly from the trans controller unfortunately. I wish they did.