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2007 chevy trailblazer_ls
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Discussion Starter #1 (Edited)
I've got the 2007 4.2L TB with the 3.42 rear end (and front) and recently did a "maiden voyage" towing my 2011 Lance Model 1685 Travel Trailer, which in my case, weighs about 4000-lb loaded. The TB did fine on flats and gentle climbs, but I hit a steep grade on Highway 1 heading toward Lompoc, CA, off of the 101, and the TB wouldn't haul faster than about 35-mph! In second gear. Damn. I'm planning some trips all over the Pacific NW and will certainly hit some serious grades.

So I have options: buy a more powerful V8 vehicle, such as a Suburban, Tahoe, or similar. Or, I am looking into changing out the ring gears on the front (carrier) and rear differentials to the 4.10 ratio. That would give me another 1000-lbs of towing capability, and would keep the engine in the power band going up grades (or so I think).

The gears are not that expensive, and even though I can handle a wrench confidently, I don't have a lift, so would spend a lot of time under the vehicle.

Anyone have any experience doing something like this? (Or just dropping in a used front carrier)
 

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2006 chevy trailblazer_lt_ext
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197 Posts
My personal opinion is to purchase a properly equipped vehicle rather than attempt to add capability to an existing vehicle.
 

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2007 chevy trailblazer_ls
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Discussion Starter #3
My personal opinion is to purchase a properly equipped vehicle rather than attempt to add capability to an existing vehicle.
I'm definitely leaning in that direction. Too bad the TB didn't meet my expectations.
 

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2006 chevy trailblazer_lt_ext
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Yes but keep in mind that it was never marketed as a work-horse, but an outdoors-y type vehicle. It existed in that weird place between the full-size Suburban / K1500 and the not-quite-a-crossover-minivan Uplander.
 

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2007 chevy trailblazer_ls
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Discussion Starter #5
Yes but keep in mind that it was never marketed as a work-horse, but an outdoors-y type vehicle. It existed in that weird place between the full-size Suburban / K1500 and the not-quite-a-crossover-minivan Uplander.
Oh, don't get me wrong, it's a great vehicle. It drives really well, it's quiet, powerful, comfortable, roomy, good looking, not too big, and easy (enough) to work on. Unfortunately I put $850 worth of new tires on it before I tried it out for towing and now I'm going to have to sell it. :cry:
 

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2008 chevy trailblazer_lt
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We experienced the same thing: a "big" trailer is tough to tow for the L6 motor and 3.42's. I was just in a local junkyard and found an L6 Envoy 4x4 with 4.10 gears, so I took out the rear end. It was a 2002. I wanted to switch rears with my 3.42 rear RWD TrailBlazer, 2008. I later realized the older 2002 rear doesn't have holes and sensors for the ABS near the ends of the axles. I'm also in a dilema like it: try to find a shop that will swap the used gear, or pay for new gear and reflash (expected to be about $1,000+ at a GM dealer), or attempt to DIY the gear swap, or try drilling the old rear, etc. etc. I think the gears may help but it may still be relatively wimpy, especially compared to a 6.0L or 6.2L if you find a Tahoe with a bigger motor. Someone reported it being night and day: towing a camping trailer with a Tahoe 5.3L (white knuckles) vs. a new Silverado 6.2L w/ 3.73's Max Tow package (power and control to spare). Good luck!

Rob in AZ
 

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I meant to mention that I visited the same yard two times, about a year apart, looking for TrailBlazers, etc., with 4.10 gears and only found one. I looked at RPO codes for GT5 on about 25 vehicles and 3.42's came up the most, 3.73's were semi-common but I only found the one with 4.10 gears.

Rob in AZ
 

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2004 gmc envoy_slt_xl
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If you're going to swap gears, I would just get a pair of differentials from a junkyard. 3.73s are very common in my area. I recently bought a 05 TB to flip that had a bad rear diff with the 3.42 and was harder to find than the 3.73. I always go to a pull yourself junkyard and the rear was only $100 and they charge $75 for the front.i personally would try that first, that way if it still isn't enough pulling power you don't have much money into it.
 

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2009 gmc envoy_slt
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If you change the rear diff/gears, do you also have to change the front diff gears as well so you don't throw off the overall gearing when in 4*4 so the transfer case doesn't have a hissy fit?
 

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If you change the rear diff/gears, do you also have to change the front diff gears as well so you don't throw off the overall gearing when in 4*4 so the transfer case doesn't have a hissy fit?
Front and rear diffs MUST be the same ratio! Or you'll have more than a hissy fit...you'll have major damage, sooner rather than later.

Honestly, towing that much weight, my advice would be to just get a not only more powerful but heavier vehicle. If your trailer brakes fail (and we all know how reliable trailer brakes are), you could be in serious trouble on a downgrade. 4K unbraked will shove a TB all over the place.
 
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