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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 15201
Experience:  GM Grand Master Technician 2007. 14 years experience.
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I have a 2006 Chevy Colorado 3.5L z71 4wd truck with 113K

Customer Question

I have a 2006 Chevy Colorado 3.5L z71 4wd truck with 113K miles. Before my last inspection in August, I went to autozone and had them check for codes due to an engine light that was on for a few weeks. Codes came up for P0106, P0128 and P0442. I know the code descriptions and have a plan to replace a few items. The bigger issue I have is that recently I noticed that the automatic tranny wasn't shifting normally. I was driving about 25 miles and every time I started a slight incline between 45-55 mph, the tranny would shift back and forth quickly from DRIVE to third gear like it couldn't find the right time to downshift. Kept having to manually shift to third gear so it wasn't so annoying. Almost feels electrical due to the rate of the back and forth shifting. I'd hold the pedal still...barely accelerating, and it was like the shift issue was in perfect time. Up,down,up,down,up,down. Not erratic. I replaced the gas pedal thinking it could be a bad throttle sensor. Recently, I read that code (P0128) could be effecting the tranny due to improper temps being read by the PCM. I'm going to replace the t-stat and temp sensor this weekend. Hoping for some positive input. Nkt sure if any of her codes could be doing anything to the tranny.....Not wanting to replace a tranny...argh!
Submitted: 10 months ago.
Category: Chevy
Expert:  cloe0626 replied 10 months ago.

when was the last time the tranny was serviced

Customer: replied 10 months ago.
Unfortunately never.
Expert:  cloe0626 replied 10 months ago.

the temp sensor could be the cause but more then likely the transmission filter is clogged this only happens if you go up an incline

Customer: replied 10 months ago.
I've noticed it once or twice on a flat area as well but always when I feel the tranny should be down shifting normally and it's just not doing it normally. I have to press the accelerator more to get the downshift. I just remembered....when cold, I put it in reverse and it seems to wait a few seconds before engaging. No clicks, no winding up before engaging, just feels like I'm pulling a trailer. A little extra gas to move the truck...only when cold. No smells, fluid looks new.
Customer: replied 10 months ago.
34;clunks" ..not clicks. BTW.... I've built many older cars and I'm very fluent in doing my own work most of the time but with all the sensors and new equipment on modern cars these days I tend to get into YouTube, Google etc to,learn and do it myself.
Expert:  cloe0626 replied 10 months ago.

ok as for sensors go the temp sensor could be the culprit but it could also be the transmission speed sensor thats causing it

Customer: replied 10 months ago.
With no code?
Expert:  cloe0626 replied 10 months ago.

it is possible