4L60E Shift Question

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1987 GMC Jimmy

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I have a question for my brother. He has a '93 GMC K1500 that he just bought and is trying to get going because his square body project has been moving a mite slow. Anyways, the ESC, transmission control, and engine control are all in the PCM as you all know. He was having some ESC glitches and a solid Code 43 so I suggested to him he replace the PCM, and he pulled one out of a junker. Truck runs great now, but now it won't move. He did change the trans fluid and filter after swapping the computers. When he shifted into gear, it just made a machine gun type loud clicking noise, and it wouldn't move. It's the correct filter, and he seated it as far as it would go into the valve body with no problems. Pump is pumping because internal rad cooler was full of fluid. It took five and a half quarts of transmission fluid, but he accidentally had one of the cooler lines off and it blew a couple quarts out. It reads right where it's supposed to in the hot range, but he filled it with the engine off, and it overflowed out of the dipstick before he got it where it was supposed to be. I thought that was a little weird only because it's never happened to me, but then again I always have my vehicles running when I do tranny fluid. It sucked it down when he started the truck, and it all read fine. I'll also note that the truck can still be pushed in park. The shifter is not sloppy, and it previously responded to its selected gears accordingly. I can't imagine that being anything other than the linkage not fully engaging park or the pawl got broken off. I told him to try the old, broken computer (same numbers, both 625's), and if it worked like it's supposed to, to try swapping the MEMCALs and see if that fixes it. He turned seventeen today and is supposed to get his license any day now so he's beating himself up for touching the fluid. The fluid was filthy and ancient, but there were no macroscopic metal fragments. Immediately before it shifted smoothly with no slipping or hard shifting, and that was only a couple weeks ago. Any opinions would be greatly appreciated.
 

yevgenievich

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I would first figure out why it physically not shifting correctly(able to push in park) and only then mess with the computer. Disconnect the linkage and with rear end in the air( with front blocked off) shift through gears manually right at the side of the transmission. If it is not correct, then drop the pan and inspect.
 
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1987 GMC Jimmy

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I would first figure out why it physically not shifting correctly(able to push in park) and only then mess with the computer. Disconnect the linkage and with rear end in the air( with front blocked off) shift through gears manually right at the side of the transmission. If it is not correct, then drop the pan amd inspect.

That makes sense. I was thinking in electronic/less dirty terms, but there is definitely a mechanical issue in play here. If it still can't park with the linkage disconnected, should I just assume the pawl is broken?
 

yevgenievich

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Verify transfer case not in neutral being a k truck
 

1987 GMC Jimmy

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Never mind. I got him to double check and it was in N. And the dummy of the year award goes to...
 

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