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4L80e not kicking down.

C

Carla

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Hi, can anyone help diagnose what's going on with this?
1997 Winnebago with 454ci Chevy and 4L80e towing a 4500lbs trailer/race car combo.
It drove fine this morning, then wooshing sound, all normal for a while then the first big hill comes and it seemed to struggle kicking down. Pedal to the floor then did, but wouldn't later, no matter what, and shifting manually 4th to 3rd didn't work either.
Stopped and found fluid low, added 2 pints, then fine, didn't smell burnt and not foamy.
All gears ok at low speed, shifts up fine, left again and it only kicks down with cruise set.
I have built my share of TH350s with transbrake but am no transmission builder and have no clue about this one with solenoids and electronics... ☹️
Any suggestions gratefully received as we are driving from Sweden to England for a drag race...
Cheers
Carla
(Team Heaven & Hell, more hell than heaven right now...)
 
That is an all electronic transmission. If it is holding a gear, you need to see if the PCM is telling it to hold the gear or not. There are a few things to look at that can cause shifting issues on late model vortec engines. Not sure about overseas, but I know here in the states a 97 454 will have a 454 vortec engine in it with multi port fuel injection. A dirty MAF sensor will cause ALL kinds of shifting issues on those engines as it uses the MAF sensor reading to determine engine power output based off of airflow going into the engine. Oiled air filters like a K&N have caused more trans shifting issues than probably any other thing has. Otherwise you need to get a scanner on it and see what the PCM is seeing, and what it is requesting it to do. Check it for codes as well.
 
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