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The A604: Troubleshooting
The A604 can and will break eventualy. When it does, you have two concerns to troubleshoot: The mechanical system of the A604 and the electrical system of the A604.
First, before you do anything else when having A604 problems: Change the fluid with new Mopar 7176 and filter. You'd be surprised how many A604's find their way to the junk yard merely because the wrong fluid was inside or the fluid was dirty. It does make a difference.
You can get limp mode or other problems with the wrong or dirty fluid in the A604.
While changing the fluid, remove the tranny oil pan and look to see what kind (if any) of debris is at the bottom. If its just the usual sludge and dirt, then chances are the A604 is still mechanically salvageable without a rebuild. If it is full of chunks of metal - chances are that something has broken and a rebuild (if not a partial one) maybe required.
With the fluid changed, check the tranny and engine mounts to make sure that they are all intact- as they CAN cause limp mode, noises, and vibrations that maybe associated with A604 problems.
See my fluid note page here for my depth on this topic
If you have done all this, and the problems are still occuring- next you must do a CVI (Clutch Volume Index) test.
An other worth while test is the Clutch Air Pressure Test, which checks the condition of the A604's clutches.
If the fluid is fine, engine/tranny mounts are all good, and the CVI test shows all good- then chances are, its an electrical problem.
First thing I would check- the speed sensor(s) on the A604. It uses two in early years, one in later years. If the sensor is bad, weak or not well connected, it can cause problems in the A604's operation.
When you replace the sensors, you may want to also buy the socket they plug into (as they can break and its nice to have spares). The dealer should be able to supply you with both.
As to cost? A solenoid pack runs abt $60 USD, a fluid change & filter replacement (if done at home) can be abt $50, a good 30-40 more if you do a full system flush, and the sensors run close to $50 ea.
I found online a .zip with pdfs from a A604 repair shop manual, which is of help/interest to people troubleshooting the A604. It can be found in the files section of the Mopar 3.3 yahoo group or the A604 yahoo group.
If after ALL this, you still have your problem- I suggest getting/finding/using a TCM code reader and/or finding a professional tranny repair shop (one fimilar with the A604). Once you get the TCM codes pulled at the shop you can get an idea what the electrical system thinks is wrong. TCM error codes are different from PCM codes and can not be retreived without a TCM code reader- these are expensive readers that not all shops have- let alone amatuer home mechanics.
Now, if all this shows you must rebuild the tranny you have several options:
1) Pay a shop to rebuild it for you
2) Purchase a already rebuilt tranny and have a shop install it
3) Purchase a used tranny at a junk yard with a 30 to 90 day warrenty
(depending on the yard) and either have a shop install it or install
it yourself
4) Try to rebuild the A604 yourself (do not advise this unless you
have rebuilt tranny's before).
Make sure your A604 is used on the same engine as whatever your engine is- i.e. a 3.0 MUST use a A604 with the 3.0 bellhousing, 3.3/3.8 uses a 3.3/3.8 bellhousing, etc. Also not all A604's will directly bolt into your car- remeber that a 90-93 must use a 90-93 A604 case, the 94-95, 96+ all are slightly different- some fabrication required to put a newer generation A604 in an older car. Note that a professional rebuild updates the A604's internals to modern specs so not much is gained by a modern A604 case in a older car as opposed to a rebuild.
-Bad speed sensor(s)
-Differential pin ejected through case
-Bad/clogged Solenoid Pack
-Bad/leaking Pan Gasket
-Overdrive Shaft Breakage
-Bad/Clogged radiator or transmission cooler
-Low/Reverse Piston retainer distorted (causes hangup of the piston-
i.e. bump shift)
-TCM needs to be updated/flashed (TCM's with fins only)
-Wrong or dirty transmission fluid
-Rear Carrier Breakage (updated part starting in 1998)