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Weird Shifting

johnpimentel72

By johnpimentel72
in Ask A GM Technician

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johnpimentel72 Enthusiast

johnpimentel72

Posted
Posted

thanks a lot i found this site. im having the weird shifting problem.

 

here's the story:

 

bought the truck a month ago its got 33k kms on it. the previous owner didnt used it for 2 years coz he's out of the country. his brother just starts the engine for a couple of minutes then off. when i bought it the service 4x4 lighted up. searched the internet, cleaned the 4x4 switch but later found out that the atc fuse was blown and keeps on blowing. we looked for any short but didnt find any. cleaned all, the grounds and contacts. when the atc fuse was now ok another problem arises. the shifting seems to be akward. hooked it up with tech2 and didnt find any codes (except for history - loss of atc class 2 communication U1026) but discovered something funny. when the shifting seemed to jump, the tech2 indicated shifting from 1st gear jumping to 4th and when it seems there's low power, downshifts doesn't happen. tested it with tech2 if the 4lo might be engaged but it says no. somebody suggested that it might be the solenoids being dirty. we changed the transmission fluid and filter, cleaned the solenoids and valve body and true enough it was dirty. while we were at it, we changed the transfercase fluid, differential fluids engine oil and filter, fuel filter, air cleaner and brake pads we also cleaned the throttle body. but still the same annoying problem. somebody suggested that i try to use manual shifting first and later on see if this will solve the problem.

the next day got P1875 - 4WD Low Switch Circuit Electrical and U1026 - Loss of ATC Class 2 Communication, gm technician had it erased coz it might be of history in nature.

 

after all these, everything seemed normal for a couple of days. then after one day of rest it went back again. no codes as of this time but i know that soon the check engine will light up again.

 

hope that anybody could help. i really like the truck and wouldnt want to part ways. i have future plans to raise the ground clearance a bit. its still fresh having only about 20k miles on it. no other problems except for the shifting.

 

2000 extended cab stepside silverado black

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