Chrysler is slowing my Dart build

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BillGrissom

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Little progress on my 65 Dart last month, due to my wife's 02 Chrysler T&C 3.8L. More ammunition to respond to those who question why I "want to deal with the problems of an old car".

Failed emission test, as expected since started missing last month, plus the tester said the PCV hose wasn't correct (try finding that in 15 years). I had to bite the bullet and pull the transmission.

As suspected, the flex-plate cracked, which messed up the crank pickup - slots in "toner ring" welded around flex-plate. The crack ran all the way around the 8 crank bolts, under the backup ring, so the outer disk spun 20 deg before wedging tight. Amazing it ran at all, though the burnt-thru and grounded wire I found behind the exhaust x-over could also have been the culprit (wire to coil pack). I had been stumped by a strange sheet-metal sound for a year until I read on the internet that is the tell-tale sign of a cracked flex-plate.

Went to the dealer, since the ebay flex-plate I bought was too new (2003+). Some dealer mechanics were hanging at the counter and said "Bet it cracked all the way around under the washer, we see that a lot". Wasn't it uncommon for flex-plates in 60's cars to fail, except maybe drag racers? Are they using cheap, brittle steel today? The new one said "made in Canada".

On the plus side for Chrysler, since pulling the tranny in a transverse V-6 AWD minivan is 5x harder than my Dart or Newport, I decided to rebuild and put in a TransPak kit. The A604 4-speed electronic was almost perfect inside - fluid clean, friction plates worn only 2 mils, so I re-used them. The mini-van has 160K mi but we got it 20K ago so don't know the history. My first trans rebuild, though I did take apart an A413 (3 spd, hydraulic) for failure analysis (torn servo seal per photo). The A413 is basically the 904/727 design and I read of the same problem. At least I now know why my son's minivan won't go in reverse when cold, which is my next "Chrysler delay". The A604 is a clever design - no bands, all shifting done w/ clutches. Despite having a computer, the valve body looks as complicated as a 904. Not sure why they still need the "hydro-mechanical computer" part. While a nice, reliable design (at least Gen3 1993+), if the computer fails or needs re-programming it can get expensive.

On my Dart's 273 engine, I added a 36-1 toothed wheel under the pulleys for crank pickup - an eventual goal is modern controls. That is simple to access. New Hemi's are the worst. I understand they cast the "toner ring" as part of the crank (think 2.4L also). I have read that some Hemi owners (truck guys) have caused their crank to fail by running under-drive pulleys, which shatters the toner ring (vibrations?). Pulling my tranny was much easier than replacing a crankshaft. Haven't read of a FABO Dart "new Hemi" failing yet.
 

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You would think ma Mopar would have been able to figure out by now how to build a damn flex plate and an indestructable 604! Oh wait, then they wouldn't have any reason to build replacement parts that will fail just the same way. Sorry for your heartache man, typical 3.8 604 combo at its finest.
 
Except the torn servo piston was from an A413 (in Voyager), which is basically the A904 in a transaxle (descendant of A404). I have read of similar "torn servo seal" problems in A904/727 transmissions and an after-market piston (Sonnax?) that fixes it. However, I can't find it anywhere. Does anybody know of such, and have the dimensions so I can check if will fit my A413 (upcoming job)? Some Neon "tuners" replace their torn servo seals regularly.
 
You would think ma Mopar would have been able to figure out by now how to build a damn flex plate and an indestructable 604! Oh wait, then they wouldn't have any reason to build replacement parts that will fail just the same way. Sorry for your heartache man, typical 3.8 604 combo at its finest.

I wouldn't... You should see the dash on my 03 Ram... or any other Ram for that matter... I am still hoping Someone comes out with a replacement dash built out of decent material that doesn't crack.
 
Make sure the crankshaft thrust doesn't have too much movement, Very comman on 3.3 and 3.8L engines. New style 604's are great transmissions. Chrysler even sold the technology to GM. Though there not very forgiving when it comes to spinning one tire, they tend to brake the roll pin off in the differential pin letting it fly out of the case.
 
I guess Im lucky. 220 000 km's and my 3.8/604 combo is still running strong and trouble free
 
I have no idea why Mopar is so hard to deal with. Their parts network just plain sucks and why when they have a huge failure rate on a part the let it go on for years just plain
poor customer service. I hate to try to get a part from MP. The last time I tried to get something I threw catalog at the parts guy and told him I would never be back. No wonder the are having problems.
 
...New style 604's are great transmissions. Chrysler even sold the technology to GM. Though there not very forgiving when it comes to spinning one tire, they tend to brake the roll pin off in the differential pin letting it fly out of the case.

I did see an after-market solution that straps a band around the roll pin so it can't fly out from centrifugal force. I vaguely recall they fixed that on later models of the A604.

Aren't all Mopar 4 spd electronic trannys the same internally as the A604? The A606 is RWD (recall) and might be what some people put in A-bodies, though must cut the floor tunnel to fit.
 
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