Allison pops out of reverse, 2-1 shift harsh

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Jan 27, 2008
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Monroe, MI
Friday after work, I got home and went to turn around and back up when all of the sudden the engine revs up, I look down to "shift range inhibited" flashing on the dash and the gear selection indicator flashing. There are were no codes that pulled up. During the drive home Friday, I noticed that I started to get harsh downshifts. The 2-1 shift is by far the worst. I pulled the pan off today and changed the internal filter, spin-on, pulled the trim solenoids and checked the valve movement (not sticking), put the pan back on, fuilled it up with fluid, and still the same problem. Any ideas?
 
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Jan 27, 2008
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Monroe, MI
I have 50K miles on the trans. I built it when the truck had 10k miles and it worked great until the C3 clutchpack went out last summer.
 
sparepartsracing

sparepartsracing

spareparts offroad&fab
Mar 17, 2010
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i think its a common problem with all of them even the ones in my gmc top kicks go all the time...pain in the balls
 
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Pushing my luck....
Jan 27, 2008
791
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Monroe, MI
Ok, I pulled the trans this morning and tore into it. C3's are wasted again, and upon further investigation I found out why. The C3 piston has a chunk of rubber missing which is causing a loss of hydraulic force on the C3 clutches. I don't doubt that this was what caused the issue over the summer also, I made a mistake by not looking everything over good enough before I assembled it......:eek:
 
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