Transmission Blues... (Caravan/Voyager AWD 1995)

I've been struggling with my tranny for a year now. Here's a description of the problem and what I've tried so far: (car has 150.000 miles). I'm about to put in a new tranny any day now, but before I start maybe somebody have some more input on the matter...

First of all, transmission works just great when cold. Problems start when it's heating up.
When engine is so warm that the LO engine fan has engaged it start to shift VERY hard to second and occasionally goes into limp mode. If I then leave the engine idling until engine fan goes into HI, everything goes bananas. It engages forward drive but when it's supposed to go into 2:nd it goes into: nothing... like neutral. At that point the only gear that engages is the Reverse, but with a loud noise. If I turn the car off and restart it does engage fwd drive but same thing happens again when it's supposed to go into 2:nd: meaning nothing. Leaving the car to cool off it works ok again.

Chrysler dealer scanned the trans and gave fault code: P1784, L/R clutch sense circuit. (How they managed to get an OBDII code from my -95 is beyond me, but anyway...)

I've been hoping it's some minor or electrical problem as it works very smooth when cold, so this is what I've tried so far:

-Change of a solenoid pack
-Changed the plastic 2/4 accumulator piston to an aluminium one
-New Output- and Input speed sensors
-Found a TCM at a wrecker's with only 50000 miles, and funny thing is that it worked great for a week! I thought the problem was solved... but nope.

I have had my hopes up that it can be something electrical related to the engine fan's engagement, but looks like it is an internal problem after all (related to heat). The thing that buggers me is that it works GREAT when cold - semi cold..
Any ideas?

Now, I bought a tested and working A604/41TE with 106.000 miles for a very good price, and am about to install it any day now. One question though:
My van is the short Voyager, whereas the trans I bought is from a Grand Voyager.
As both are 3.3's, AWD and 1995 it should however be exactly the same transmission huh?

Any input much appreciated!

/Mat

 

Do you have the correct fluid in the transmission? It would do a lot of
the weird stuff you're talking about if you put in Dexron.

 

This smells like an electrical problem to me! And by that I mean cable
harness / wiring - not parts!

The fact that the new TCM worked for a week speaks volumes.

It is were me, I would have taken it to my local "guru" transmission
shop. They are absolutely kick-ass with stuff like this. And the have
dealt with litterally thousands of A604s over the years. They have a
dedicated "team" of mechanics who do NOTHING ELSE. They fix at least 7
per week.

Since, however, you do not have a shop like this on-tap, and like
doing things yourself (for the moment), I would take some time and do
an INTENSE physical inspection of ALL wires and connectors in
transmission realted cable harnesses. Pull apart the connectors, and
clean them with a contact cleaner, and then apply a contact
preservative. Make sure that all wires sound - look for chaffing, worn
insulation, cracks, intermittent wires...

Heat will cause things to expand. I almost sounds like the expansion
is significant enough that something shorts out. If there is any
oxidation or contamination in the connectors, then it might short out
as the temperature rises.

I am also curious about the idea that the problem shows up when the
fans kick in.

Put a scope on your +12V supply wires. Since cars are equipped with
Alternators / Regulators, you should see some "ripple" on the +12V
supply while the car is running. Ideally, the ripple would be quite
small. Watch your +12V lines as the fans kick in. Fans are motors. It
could be that the fans are introducing excessive ripple or noise into
the voltage supply for your TCM. If there are spikes or noise being
induced into the system, then it might cause the TCM to freak out.

Alternatively, if your alternator is having problems, then the
increased load might be causing the regulator to not regulate so well.
Look at the voltage with a scope. Make sure that you are getting about
13.7V on your +12V line with the car running. And again look at the
noise (the "AC" component). If you get excessive ripple, then try
turning on the headlights as well. If the ripple gets larger as the
load gets heavier, then you may have an alternator problem. (Long shot
on this one, but hey, it is easier to check than re & re a
tranmission!)

And keep us posted on your progress.

 

I concur - however don't overlook the role of the input and output
speed sensors.

If your going to do your own R&R this might help:

http://freebsd-corp-net-guide.com/94tcpics/project.html

That can sometimes cause more problems.

A better way is to start with the connectors on the transmission, the ones
to the sensors are right under the oil lines, these lines often leak oil
down
over the sensor connectors which over time rots the rubber plugs.

Only work on a group of connectors at a time, not all of them in
the harness. Do one, then drive, see if problem goes away. Repeat
with next connector, if not.

It can also cause the speed sensors to go bad.

That would only happen if the + power line to the TCM had a high
resistance connection to the battery +. Otherwise, the battery
works as a surge suppressor.

Once again, all this is smoothed out by the battery.

Ted

of the problem and what I've tried so far: (car has 150.000 miles). I'm
about to put in a new tranny any day now, but before I start maybe somebody
have some more input on the matter...shift VERY hard to second and occasionally goes into limp mode. If I then
leave the engine idling until engine fan goes into HI, everything goes
bananas. It engages forward drive but when it's supposed to go into 2:nd it
goes into: nothing... like neutral. At that point the only gear that engages
is the Reverse, but with a loud noise. If I turn the car off and restart it
does engage fwd drive but same thing happens again when it's supposed to go
into 2:nd: meaning nothing. Leaving the car to cool off it works ok again.sense circuit. (How they managed to get an OBDII code from my -95 is beyond
me, but anyway...)that it worked great for a week! I thought the problem was solved... but
nope.engine fan's engagement, but looks like it is an internal problem after all
(related to heat). The thing that buggers me is that it works GREAT when
cold - semi cold..very good price, and am about to install it any day now. One question
though:

 

Provided, of course, that the battery is in good condition.

I had a battery go intermittently "bad" on me once in my 94 Acclaim.
Holly Hana, you would have thought the car was posessed!

I figured for sure that I was looking at a HUGE repair bill. After 5
min in the shop, the battery was diagnosed and replaced for about
$100. I was skeptical, but it worked!

In general though, you are right, the battery looks like a HUGE filter
capacitor.