The A604 is the Achilles heel of the Avenger and Sebring and everyone knows it. They break under stock conditions, and they break under moderate engine mods. In some cases they explode, and it has less to do with power and more to do with design. When properly built, the Trans can handle a decent amount of power input, but it is important to keep up with maintenance and get the build done by a reputable shop. We’ll outline some of the major problems in dealing with the A604 and the ways to counteract or alleviate those problems all together.
The first and most frequent killer of ANY transmission is heat. When you are putting power to the transmission, clutches create a ton of heat. This in turn breaks down the transmission fluid causing accelerated wear on the clutches, seals burn out, and you’re in for a big bill. Transmission fluid generally starts to break down at about 240F degrees that are when the fluid starts to get thick and varnishes. This clogs and sticks in passages or clutches and prevents parts like the solenoid pack from doing a good job of shifting gears. At around 265F degrees or so, you get to the threshold of the seals. They can only take so much heat and at this temp they start to get rigid thus creating internal leaks. Internal leaks cause loss of line pressure, and when you have poor line pressure holding a gear is harder. The clutches aren’t pressed to the steel plates hard enough and they wear faster; you’ll notice your fluid turning brown or potentially black if it’s severe. At 300F degrees your fluid is so bad; the clutches start to slip more often. This refuse can cause clogged filters, and clogged ports on the shift solenoid. Heat starts to build even more and once you hit 315F degrees… your seals burn out, clutches are burned out, and you build up a nice concentration of carbon filled gritty fluid. How do you prevent this? You probably already know the answer to this, but it with an aftermarket inline cooler. The stock system has a cooler built into the radiator, but it is small and is highly inefficient. Most people pick up the popular line of B&M Super Coolers. They work great and you can run them in tandem with the stock cooler for even more efficiency. Truth is any 6 Pass cooler will work, and do the job perfect. There is such a thing as TOO BIG when it comes to Trans coolers though. If you run say a 10 pass cooler in tandem with a stock cooler and leave for work on a cold morning. You’ll notice your car is holding second gear a lot longer than it usually does. This is the Trans going through a warm up mode trying to get the fluid to optimum temps for operation. It’s not bad for the Trans per say, but it’s annoying if you hit the gas and it sticks in gear and then pounds into third gear. The temps you want to stay around are 185-200 degrees; those are optimal temps for good life of the Trans and better power transfer.
The second most frequent problem is the differential idler shaft. I myself have been victim to this little chunk of hatred, and it almost cost me a car. The idler shaft is a round chunk of metal a little over ½ inches in thickness. This shaft sits inside the idler gears which in turn rotate the spider gears in the differential. This shaft is held in by a pin which from the factory is pressed in, and then the surrounding differential carrier material is pinched over it to attempt a lock on the pin. The shaft itself does exactly as it says and remains idle holding the gears in alignment in the carrier. There are many ways for this part to fail, a lot has to do with oiling and leads us back to the cooling. The shaft sits static, while the spider gears turn the idler gears which rest on this shaft. The speed as you can imagine is high and if oiling is poor, the heat builds and those gears weld themselves to this shaft. This causes catastrophic failure and generally leads to the shaft snapping and going through the case of the transmission. Heat is probably a part of nearly all the failures in the transmission. Doing one wheel burnouts in parking lots causes’ heat and also forces the gears and shaft into an uneven balance. When you are spinning that one wheel, the gears can come out of their alignment and start to bend and grind on that shaft. This creates shrapnel and in turn goes parading through your trans clogging and cutting seals as it goes. If this doesn’t kill the differential, the retaining pin will. This little piece of metal is responsible for hold that shaft from going out of carrier and from rotating with the idler shaft. If this pin were to come out, you guessed it. If the shaft seizes on the idler gears, it will tear that pin off and then the party begins. How do you fix ALL of this? There is no bullet proof way to do it in the A604. Companies like Quaife or Kaaz manufacture differentials that are nearly indestructible and if they do blow they’ll replace it. I myself have never seen one fail, so if you have that available in your model Trans I envy you. Now, for us poor A604 owners with no Quaife option, there are a few alternatives.
• You can have the retaining pin welded into the carrier, this is OK, but it won’t solve most of your problems.
• You can have the idler shaft straps installed on the carrier to keep the pin from damaging the case when it comes flying out. These little things hold the pin from the outside.
• You can install a limited slip differential. I don’t really promote or like versions like the Phantom Grip limited slip. These use metal to metal contact to evenly distribute power (or attempt to) to both wheels. They claim to be torque sensitive and put power evenly under acceleration or cornering. I’m not sure how a spring and metal block can sense a biased torque condition, but hey I’m no genius either. If that doesn’t deter you, think about what metal to metal contact does… The other alternative to the Phantom Grip is to install a clutch style limited slip. These use clutch material instead of metal plates to lock the gears into an even output. Instead of springs, they use a series of washers and shims to properly set the tension on the gears so you can set for your power needs. With a unit like this, all parts of the differential are modified to promote oiling of the gears and the shaft and items like the retaining pin are upgraded to stronger materials.
Now we get into the internal parts of the transmission, the guts. Say your Trans is going or you plan on putting some decent power through there and want to be safe. Time to rebuild with some beefy parts you say, but don’t know where to start or what to look for. I’ll lay out the parts I look for in a performance build, and also explain why I chose these parts.
• Raybestos Carbon Kevlar Clutch Kit- These are a much better alternative than the stock asbestos material inside your transmission from the factory. Kevlar lasts longer, grabs better, and both of those lead to great power transfer and longer life of the Trans. You can get these at just about ANY rebuilder, the 604 is a very common rebuild trans, so places like Cotmans, Amco, or Bob’s Local Trans store should have plenty in stock. These usually come with everything you need for a rebuild if the trans hasn’t had any hard part damage to the planetary gears or other parts.
• New Steels – Steel plates are what sit between your clutches in the clutch hubs. This is what the clutch locks up against and these take a beating. Most rebuilders will mic the plates for flatness, heat marks, or check for them to be out of round. If you are spending the money to have it torn apart anyways, spend the money for the new plates and save yourself the trouble.
• Front pump modification – This isn’t needed, but if you are putting some decent power down you need all the line pressure the computer will let you have. Most rebuilders know enough to modify the front pump to raise the pressure. Too much pressure though and you’ll experience shifting problems and your trans will go into limp mode. Most rebuilders in the know will understand what you are asking for, for most of them it is a standard practice even on stock transmissions.
• Shift Improver Kit- This isn’t going to be like the shift kits you see for the TH350’s or the like. The TCM prevents any insanely high pressure from damaging the trans, therefore you aren’t going to get tire chirping shifts. This basically shortens the shift times between gears and also raises pressure enough to get the clutches to grab harder and faster. This prevents wear on the clutches and also makes acceleration a lot quicker. If you can’t feel when you are shifting into gear, you have problems and your clutches are riding together too long before grabbing. BAAAAAAAAAD.
• With the shift kit, opt for the aluminum accumulator pistons for the valve body. Stock is ABS plastic and with heat and time they can crack.
• Upgraded Solenoid Pack- If you have ever listened to your car when you stop, or shifted into gear you’ve heard it. CLIK CLIK CLIK CLIK! The fast sound is you shift pack routing fluid to parts of the transmission for gear selection. In late 2003 a new pack was released that is nearly silent even with the sound shield off. In fact, these are designed to run without this cover.
• High Stall Torque Converter – Torque converters transfer and convert the power from the engine into power to the trans via the input shaft. The stall of the converter is judged by how many RPM’s are needed to build up the fluid pressure enough to make the converter transfer power to the transmission. Stock is around 1800-2000rpm. By raising the stall, you can brake torque the car and push the RPM closer to the engine’s powerband. So, if you get a 2600 stall converter, you can now stall the converter until 2600RPM and get a better launch along with more acceleration. There are other internal mods they are offered in converters that increase the torque multiplication (example - 1lb of torque comes into the TC, 3lbs comes out to the transmission etc etc) Other parts include needle thrust bearings which decrease friction.
Now that you have your new trans, you have to take care of it. Maintaining a built trans is the same as maintaining your stock trans. Only use Mopar 7176 Trans fluid or approved ATF+3. You can switch to +4, but the cost is higher and finding +4 anywhere but a dealer is a chore. Change your filter every 30-40k and make sure to get the correct year and model for your car. I use the dealer for this because the OEM replacement works best. While you are there ask for Mopar Anti Foam. This little bottle gets poured into your transmission and prevents foaming of the fluid. Bubbles compress and you have bad line pressure, this eliminates bubbles. Caring for your transmission takes only a few minutes each time and saves you money in the long run. If you take care of it, it’ll take care of you.
Hope this helps you guys, let me know if I need to clarify something a little more. This will also be available on the ERT site soon along with a few other articles about V6 performance ETC.
This post isn't a bible, just an idea of what to expect from your trans. Just because your car is stuck in limp mode or shifting hard, does not mean you have to get a rebuild. If your shop tells you that, get another opinion. It could be something as simple as a blown Reverse lamp fuse (yes the reverse fuse will cause an SRS light and keep OD from working, then put you in limp mode) A lot of shops will give you a bill before trying anything.
You don't have to get the pumps modified or any of that stuff. Our Chicago V6 Turbo test car is running a STOCK rebuild with the basic OD, 2-4 clutch pack upgrades and has been shifting perfect for almost a year now. As long as they perform the new technology upgrades, you should be fine. My post was to those wishing to get the most out of the trans.
General costs for just a basic rebuild with labor are 1300+ depending on Geographic location. ERT has had transmissions rebuilt for locals for 1300 dollars with upgraded internals. This was just people dropping the Trans off, and coming back in a week when they were done. They are dyno tested before, and dyno tested after to ensure proper pressures and operation. Upgrades like the Limited Slip are extra items that are available.
There is no PERFECT differential for the a604, just the lesser of 2 evils. From our personal experience, the phantom grip loses grip fast and needs constant readjusting. The Retrofit lasts longer, but will also need adjustments down the road. There are more expensive options like the Quaife that we have modified to fit inside the A604. This is a more expensive option, but again is as good as you can get. We have a line on another company overseas that is building a torsion style limited slip that can be modified to fit the A604 as well.
My advice is to never take your trans to some oil change place and get a flush, chances are they are morons and will pop Dexron with an additive in there because they heard it was the same thing as ATF+3..... it's not. You can change the filter yourself, to completely cycle the fluid you need a shop's machine or some creative work to make your own flusher.
The A604: TCM Error Codes
The A604 has a very advanced (for its time) electrical system which uses sensors, computers and all kinds of goodies to try to troubleshoot the A604 in real time. This can help prevent damage by turning on limp mode when something is thought to be broken.
Chrysler's main flaw with this system is that it requires a TCM code reader to get the codes- this is an expensive device that not everyone can afford. Fortunately someone has developed an experimental DIY-code reader.
After getting a code reader, building a code reader or paying a shop to get the codes off of the TCM, you can get an idea what the TCM thinks is going on- which is uber helpful in A604 troubleshooting.
Here is a list of codes that cause limp mode
Error Codes That Cause Limp: 11, 13, 14, 15, 16, 17, 18, 20, 21, 22, 23, 24, 25, 26, 27, 31, 32, 33, 36, 39, 41, 42, 43, 44, 47, 50, 51, 52, 53, 54, 56, 57, 58.
 
Now here is a nice chart that tells you what each code stands for:
Error Code    What the TCM thinks is wrong
11    Internal A604 Controller
12    Battery has recently been disconnected
13    Internal A604 Controller
14    EATX Relay Always On
15    EATX Relay Always Off
16    Internal A604 Controller
17    Internal A604 Controller
18    Engine Speed Signal Circuit (RPM)
19    CCD Bus Communication with PCM
20    Battery (Switched) Connection
21    OD Pressure Switch
22    2/4 Pressure Switch
23    2/4 & OD Pressure Switch
24    L/R Pressure Switch
25    L/R & OD Pressure Switch
26    L/R & 2/4 Pressure Switch
27    All Pressure Switches
28    PRNDL switch signal
29    TBPS signal
31    OD hydraulic pressure switch
32    2/4 hydraulic pressure switch
33    OD & 2/4 hydraulic pressure switch
36    faults immediately after shift
37    solenoid switch valve stuck
38    lockup controller
39    gear ratio fault
41    L/R solenoid circuit fault
42    2/4 solenoid circuit fault
43    OD solenoid circuit fault
44    UD solenoid circuit fault
45    internal A604 controller
46    Gear 3 to Gear 4 shift aborted
47    solenoid switch valve stuck
50    gear ratio fault in R
51    gear ratio fault in Gear 1
52    gear ratio fault in Gear 2
53    gear ratio fault in Gear 3
54    gear ratio fault in Gear 4
56    turbine/speed sensor fault
57    output speed sensor fault
58    sensor(s) ground fault
60    improper L/R volume
61    improper 2/4 volume
62    improper OD volume
63    improper UD volume
Ok, the two charts above get you a basic idea of what’s going on- I have yet, but may in the future, add a more comprehensive description of what each TCM error code is- however I do not yet have the time for this. In the meantime, hopefully this will be of some help!

The A604: Troubleshooting
The A604 can and will break eventually. 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.
If you have done all this, and the problems are still occurring- 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 familiar 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 retrieved without a TCM code reader- these are expensive readers that not all shops have- let alone amateur 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 warranty (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- remember 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.

Good job and it should be noted that just to be on the safe side, go ahead and use ATF+4. Valvoline NO LONGER makes the ATF+3. As far as i can tell, it has been stripped from the market.

mods, please move this as you see fit:

Question on training the transmission: When I have replaced the battery, or have had it disconnected, I never did the off-road test. I only had my driver's manual and it has it's own little instructions which is a "training" on the road. I am wondering if this is then an incorrect printing in the owner's manual.

It would seem odd that one would have to go through this very laborious procedure when their battery dies b/c, say, they left the lights on, or the battery is just old.

If you have a 2.5 engine, you do need to clean the throttle body because when the battery has been disconnected the ecu looses its memory and the idle will be low or stall. Also with the dodge scan tool DRB3 you can also perform a clutch test on all, but 4th gear. The spec for overdrive cvi is 75 to 150. If you are much higher than 150 there could be a problem with the overdrive clutch pack.