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Many times, a transaxle that the dealer or transmission shop says is
"not repairable" can be fixed with the simple steps outlined here.
Don't give up hope just because a mechanic or two says your transaxle
needs to be replaced. Many transaxle problems can be cured by changing
the fluid and retraining the computer.
When you change your transmission fluid, always use the
recommended fluid. As of this writing, ATF+4 is used in place of ATF+3 for older models. It's best to not mix the two, but the rule of thumb is that you can top off an ATF+3 system with +4, but you should not use +3 to top off a +4 system.
Don't just assume your mechanic or dealer knows what fluid to
use - ask and make sure it's the right one. If they do not or cannot
provide the correct fluid, then go somewhere else that does.
Chrysler has now licensed companies to blend and sell ATF+4 fluid. Four companies that are currently approved ATF+4 blenders are Petro-Canada, Shell, Valvoline and ExxonMobil. These companies have to submit to Chrysler testing to ensure quality, so you should feel safe using these brands of ATF+4 fluids. Mopar branded ATF+4 fluid is sold in most Wal-Mart stores. Petro-Canada, Shell and Valvoline offer their fluid to other companies to be rebranded or private-labeled as well.
If you suspect that Dexron has been put into your A604/41TE,
invest the $40 or so to have it replaced immediately Dextron is a
"grabbier" fluid - the A604/41TE is designed to slip a bit during
shifts - and ultimately it'll cause the transaxle to fail.
Ask your dealer about updated firmware for the transaxle
control module (TCM) - changes are made from time to time that can
eliminate or reduce problems such as "bump-shifts" or a shuddering
torque converter. Some dealers are better at this that others - some
may do it for free - others may charge for it. Call around.
Common failure points include the speed sensors - both input
and output - and the solenoid packs. The solenoid packs can become
clogged - especially if the wrong fluid is used. Failure of the speed
sensors can trigger "limp mode" which causes the transmission to only
use first and second as a very visible sign that something is wrong.
You should be checking the computer for error codes at this point.
Information provided by Steve Martinez...
The A604 is the Achilles heel of these cars 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 is 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 no 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 bulletproof 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.
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You can have the retaining pin welded into the carrier, this is OK, but it
won't solve most of your problems.
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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.
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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.
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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.
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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.
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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.
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Shift Improvement 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.
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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.
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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
ATF+4 as well. 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.
Steve Martinez
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