Rear gears in my 2003 Trailblazer

How can I find out which gears I have in my rear diff? The TB comes with 3.42, 3.73 and 4.10 gears available. I want to upgrade to the 3.73 or 4.10 gears for more towing capability, anyone suggest which one?
Also, how hard is it to change the gears? I know I'll have to reprogram the speedometer, do I need a dealer to do that?
Regards, Mike
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If it is 4x4 your looking at changing both ends. It is NOT a DIY item unless you have LOTS of practice with gearing. All in your probably looking at between 2000.00 and YES the computer does need to be reprogrammed, it controls much more than just the speedometer. Shift points, engine management and the ABS system are slightly different depending on gear ratio.
As to the current ratio, look in the glove box for the options sticker. On it look for a code that has GU in it and post it here. That will tell you what the gearing is. Keep in mind that just because you increase the gearing that does NOT increase the braking ability. Make sure your brakes are rated for the higher amount first or you might be better off trading up. The brake capacity is also on that option code sheet.
--
Steve

"Mike Brancato" < snipped-for-privacy@mikebrancato.com> wrote in message
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How much weight do you plan to pull? That`s the big question.
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Mike here's a link to TB's rpo's. It's for an '03 but it shows what the various codes in on the inside glove box means. If you have an '04 in all probability it will still give the the correct codes for the axle ratios and be mostly correct. http://snipurl.com/TB_rpo
I think the trailer weight and the terrian where you'll tow it would dictate the "best" axle ratio. If you don't have a trailer yet you might give it a try before spending big bucks to change the axle ratio.
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I`ve had trucks with everything from, 3.08-4.10. The biggest thing you`ll notice is MPG`s I would stick to 3.42 or 3.73. I`m not for sure,but I bet you most likely have,the 3.42 or 3.73
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