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2006 chevy
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25 Posts
Discussion Starter #1
I have a 2006 TBSS AWD with 90K miles on it. The only mod is a K&N air filter. For the last ~5K miles the transmission has been shifting very hard between 1-2. It doesn't matter whether I am accelerating hard or soft prior to the shift, whether the engine/transmission is hot or cold, it does it all the time. Since it started happening I have been letting off the throttle quite a bit just as the shift happens, this doesn't change the firmness of the shift but I feel it puts less strain on the drivetrain. I have avoided the dealer because I don't have the extra $ right now for them to diagnose it for 2 hours, scratch their head, and then charge me for some other thing that doesn't fix the problem. :suicide:

I have rebuilt several engines before but never an auto trans, but if it is some thing strait forward like removing the valve body and cleaning it out I think I can handle that.

Has anyone had a simillar problem?
Any thoughts on how to fix it myself?
If this is best left to a dealer or transmission shop, where can I tell them to look?

Thanks,
Dave
 

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Northwest Chapter
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11,824 Posts
Clean the MAF, if the K&N has dripped any oil into the incoming airstream and coated the MAF wires, the reading can become compromised. Side effects of a dirty MAF are hard trans shifts because the TCM is commanding 100% line pressure as it doesnt accurately know how much airflow (and therefore power) the engine is making.

Clean it and report back, cost you $5 for a can of MAF cleaner (DONT use brake cleaner).
 

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2006 chevy
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Discussion Starter #3
Cleaning procedure...

Thanks for the response, is it as easy as just taking the filter off and spraying the MAF senser (with the special cleaner) with the MAF still mounted to the air duct? Should I wipe it down with a clean rag as well or just the spray with no wiping? If this is all it is that would be killer!! :woot:
 

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Northwest Chapter
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11,824 Posts
Thanks for the response, is it as easy as just taking the filter off and spraying the MAF senser (with the special cleaner) with the MAF still mounted to the air duct? Should I wipe it down with a clean rag as well or just the spray with no wiping? If this is all it is that would be killer!! :woot:
Remove the airbox, air filter, entire intake duct from the truck. Then remove the MAF from everything else and spray MAF cleaner onto the element. If you can get a clean (read new) rag/towel in there gently wipe it. Make sure NO oil from your hands gets onto the element.
 

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2006 chevy trailblazer_ss_3ss
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8 Posts
dude you are a genius, this worked for me! Ever since i bought my tbss about 6 months ago its been shifting hard, but i just did this and now it shifts like a cadillac! Great advice, thank you very much. Well worth the 7 dollar can of maf cleaner and less than an hour.
 

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2006 chevy trailblazer_ss_3ss
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8 Posts
I don't believe the I-6 in you ascender has a mass air flow sensor, i could be wrong though. :confused:
 

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2003 chevy trailblazer_ls_ext
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70 Posts
i want to do this real bad!! can someone put it in beginer's terms? I've replaced my brake pads so i figure i can do this... I have a 2003 ext 5.3
 

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2003 gmc envoy_slt_xl
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325 Posts
Hmmm... I am a mechanical idiot so I don't know if I am the best to give advice here, but here goes ...

Your 5.3 has the air filter box on the passenger side at the front of the engine compartment. If you have your hood up it is on the left side ... I believe that it has three bolts you have to remove. When I replaced my air filter there is a cross bar that I had to remove if I recall. If you open that air box, you can follow the plastic channel down to a "square" which is about the size of your fist. That "square" is the MAF sensor, and if you remove it, it will look kind of like a steel grid to you.

If you remove this (you will have to disconnect the wiring to it) you can carefully clean it with MAF cleaner and a brand new cloth ... do not get oil from your hands onto the grid or other contaminants ...

My nephew actually had a similar issue with his vehicle, ... running lousy, all he did was put in a K&N filter and 6 mos later he had problems ... cleaning of the MAF and throttle body got it back to running properly. You have a 5.3 so I doubt that your throttle body is that dirty, but I did clean mine anyway.
 

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2003 chevy trailblazer_ls_ext
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70 Posts
I cleaned my MAF. I noticed no difference. Anyone think resetting the computer "unplugging the battery for a while" would help anything?
 

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2003 gmc envoy_slt_xl
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325 Posts
To be honest, when I cleaned my throttle body I did disconnect the battery. So did my nephew when he did his ... I thought that it was just standard procedure. I don't know if it will help, but it should be disconnected when doing these cleanings ....

I guess since you are done you can just disconnect it now for a half hour.
 

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2006 chevy trailblazer_ss_3ss
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mine was good for about five miles after i cleaned it, started hard shifting again, so i cleaned it again. this time no difference. maybe i will unhook the battery for a little while like you said and see what happens. its pretty annoying because i lift off the gas so it dosent shift hard. i shouldnt have to do that!
 

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2008 chevy trailblazer_ss_3ss
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2 Posts
Hard Shifting 1-2

I’m glad I’m not the only one with this issue. That’s awesome that we have a website like this so I can learn how to do things myself. I’m going to try cleaning the MAF and see if that works. AWESOME!!!! :)
 

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2007 chevy
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89 Posts
I had the hard shift issue at 80,000 miles. The dealership replaced the catalytic converter for free as it was still under warranty. No issues since, and I never touched the MAF.
 

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Envoy Hard Shift 1-2

Was the service engine soon light on for either the MAF problem or the catalytic converter? How can I diagnose the catalytic converter?
 

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2004 chevy trailblazer_ls_ext
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3 Posts
If your trans shifts late or is hash. Check your transmission pressure control solenoid valve. check for a code.
 

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2003 chevy trailblazer_lt_ext
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41 Posts
A couple of items to add here...

1. Clean your MAF with "MAF" cleaner only. Spray it on after it has cooled, I wouldn't recommend wiping it at all.

2. If you think you need to wipe it, spray again, and get rid of the oiled K&N filter and go with a dry K&N filter only.

3. Before your reinstall your MAF sensor, allow to completely dry...

Its a very simple sensor, but if its coated in oil it WILL be very very very hard on your tranny...
 

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2003 olds bravada
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5 Posts
I replaced the transmission valve body on my daughters 2002 TB for hard shifting between 1st & 2nd gears. Problem never came back.
 
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