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Discussion Starter #1
I've got a 5.3L 4WD 06 CCSB Z71. It has the 3.42 gears, K&N intake, new E3 plugs, aftermarket muffler, hypertech tune (just running 87 performance and adjusted for my tires), and tires that measure 33.25".

The truck downshifts when going over the overpasses, and works pretty hard just towing my 12' trailer with my side by side on it. It's always been like this since I bought it about 6 months ago.

My buddy thinks it's my cat converters are plugged up. Well, in my experience if they are plugged up enough to cause engine power issue then they tend to be noisy, these are not, i've even got under neath the truck and banged on them and no rattles. I have a temp gun at work and just keep forgetting to check the temp of the cats and piping to see if they are heating up alot. But I think if one is plugged they will be extra hot, right?

So, is it just these 3.42 gears? or do i have a mechanical problem?
 

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Mmm Sandwich
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15,679 Posts
Your gears are the problem. I have owned 2 trucks with the same gearing and tire size you have. Towing sucks and hills for that matter
 

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Married and broke
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1,854 Posts
Most people with 33's seem to go with 4.30 gears. You might want to invest in a hand held tuner so you can update your truck with the newer gearing and have everything work like stock. Or get a tune from Blackbear.
 

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Discussion Starter #4
Most people with 33's seem to go with 4.30 gears. You might want to invest in a hand held tuner so you can update your truck with the newer gearing and have everything work like stock. Or get a tune from Blackbear.
Ya, i'm running a handheld to adjust for tire size.






Thank yall, I was kinda figuring these gears were my problem, just wanted to confirm that. 4.30s??? wow, that's a big jump. I was thinking high 3.9x or 4.10s max. I do 80% of my driving at 75MPH just going to work.
 

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Married and broke
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1,854 Posts
If you've got the 6sp auto, the 4.30's will make use of the trans better and take some stress off of it. Figured this, Chevy's towing package bumps the gearing up to 3.73 over the 3.42's. So, a set of 4.10 or 4.30's will help you on towing AND the 2" larger tire. Anything below 4.10 is a waste of money for you.
 
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