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2008 chevy trailblazer_lt
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16 Posts
Discussion Starter · #1 ·
2008 LT 4.2 180,000 miles. Notice I get a vibration or resonance occasionally right before downshift when climbing a hill at highway speeds. It "seems" like its not downshifting until I get a slight lagging of the engine. Other than this truck is great, just worried about the new noise.

Any ideas where I should start? Btw, not sure if trans filter has ever been changed.

Thanks!
 

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Premium Member
'05 Chevy TB EXT
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5,642 Posts
1. SERVICE the unit now --- filter and pan gasket --- don't flush until you get some idea of the condition of the gunk in the pan and filter.
Use synthetic fluid and the pan gasket MAY be reusable --- check it out.​
It should take about 6-7 quarts and the synthetic will mix nicely with whatever is in there now.​
2. We have other tests for you --- later --- after you service this unit!
3. Do it tomorrow --- or better: tonight --- sleep is seriously overrated.
4. Report back ASAP.
5. I'm waiting!

PS --- what you are describing is a potential 4-3 downshift hang-up (that means a potential forward sprag failure is possible when it comes outta freewheel and is asked to apply under a lot of power ....... or not) --- it happens --- but I need more info.

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2008 chevy trailblazer_lt
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16 Posts
Discussion Starter · #3 ·
Thanks Ravalli Surfer! The truck is parked right now as we deal with relatives and Thanksgiving meal. Soon as everyone gets out here I'll start. From what I've been told that might be Tuesday.
 
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