904 Conundrum

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n3w6uy

The Valley Ant
Joined
Dec 19, 2008
Messages
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Location
Paducah, KY
So the 904 in the '73 Valiant was toast, or so I thought. I was missing Reverse and Third gear, the most important two. I knew the 904 in my '72 Valiant was good (both are 225 SL6ers) and the '73 was my daily driver, so a quick swap fix, right?
:angryfir:
Wrong.
:banghead:
The swap was more of a PITA than I thought it would be, but I finally got the trannys swapped, supported, sealed, tightened, and filled with fluid.
:hello1:
And I have the same problem...kinda.
:scratch:
Reverse takes a little bit longer to engage than I'd like and there is slippage between the gears. Sometimes a neutral slip, sometimes a slip to the next or last gear.
:wack:
I know little in the ways of automatic transmissions and what makes them know when to do their thing, or what interrupts that sequence.
Can someone please provide a light into what the heck is, or could be, going on?
:prayer:
The car afflicted:
73008.jpg

she misses being driven...
 
If the one that you put in was good (didnt slip or give any problems driving around in the other car) and it magically started having problems I would think that some of your gear selector linkages may be out of adjustment. Are you sure that they have enough fluid, and did you check it idling in neutral or park?
 
X2 and if those check out fine, it's probably throttle linkage adjustment. Next order of business would be a full pressure test to determine the problem.
 
it will take a few fills and checks to get it completely full of fluid. and run time in between along with going through the gears. you are checking the fluid in neutral ? it will feel lazy even a pint down.
 
Those problems may seem similar but they probably are not caused by the same malfunctioning part(s). Since your first trans. lost 3rd and reverse that means the front clutch pack was burned up or blew a seal, but most likely it burned up. When that happens burned clutch material settles in the cooler (the one in the radiator that the trans. lines run too) and most likely your new trans. now has a plugged filter because of the old gunk that was in the cooler got pumped into the new trans. Drop the pan and clean it, replace the filter, adjust the bands (the rear band if out of adjustment can cause slow engagement of reverse and if the front band is out of adjustment it'll let it slip when shifting), flush out the cooler with cooler flush, install the pan and fill it with fresh fluid checking it in neutral. Probably take 4-5 qts. Test drive it. If it still doesn't shift right check the throttle pressure linkage adjustment. It should go all the way back or nearly all the way back when you floor the throttle. If it doesn't adjust it so it does. If you go too far it may want to hang in gear too long so it's a balancing act on getting it adjusted and may take 3 or 4 shots to get it dialed in. Any time you replace a trans. cause the old one was burned up YOU MUST FLUSH THE COOLER, No if's and's or but's. If you don't you will likely have problems or at the least take some life off the new trans. If you happen to use the torque converter from the trashed trans. in the new trans. it's a double whammy. Never do that unless you have it flushed and checked. Wouldn't hurt to also check the shift linkage adjustment too like 72swinger said.
 
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