Whats My Rear End

[jrod332]

Would anyone know what gear ratio I have. I have an 05 silverado with a 5.3. And how does it compare to other ratios?

[Matt_]

you either have 3.42s, 3.73s, or 4.10s.... you have to look at the codes in the glove box to see what gears you have .

 

What exactly are you trying to figure out? Usually you compare ratios for a specific application... ie: larger tires, performance, mpg, towing, etc. They all have their benefits in their respective areas.

[jrod332]

I am just curious where my truck stands with the others. I just started towing a trailer for work. All the different ratios confuse me how they can have different benefits. Which code would it be out of the hundreds that are there.

[ShoddyHog]

I am just curious where my truck stands with the others. I just started towing a trailer for work. All the different ratios confuse me how they can have different benefits. Which code would it be out of the hundreds that are there.

 

At any given speed, a higher ratio will allow the engine to stay at a higher RPM (and have more power) than a lower ratio. That also helps greatly with towing heavy loads up grades and such. Mileage suffers.

 

A lower ratio will allow you to get much better mileage, but will work your engine much harder towing.

 

Same applies to cars. My next mod for my car will be replacing my 3.64 gears with 3:91s. I'll lose a little MPG out on the road, but I'll get a much better quarter mile time becaus I'll be able to get my 3,750 lb. car moving faster.

[nbscanuck]

If you are towing the higher the rear gear number, the better. It will give you more torque to get things moving. The down side is that you are going to turn more RPM when you are empty and get slightly less fuel mileage.

[txab]

AS stated check your glove box for RPO codes.

 

Here are a few in this post:

 

http://www.gm-trucks.com/forums/index.php?...st&p=391538

 

Also there is a RPO decoder here.

[Matt_]

Here's my quick summary to give you an idea of where you're at, after you look up your RPO codes (Note: applies to the OP's truck which has the 4L60E):

 

3.42s: Good gear if you never tow and don't want larger tires. Will yield best gas mileage with stock (or smaller) tires especially on the highway.

 

3.73s: Good gear if you tow on occasion and retain stock tires. Will do alright with up to a 33" tire, but will struggle with larger tires and towing on the highway. Unloaded, will yield pretty good gas mileage. Also is a good gear for performance trucks that are daily driven with a driver who's conscious about gas mileage.

 

4.10s: Good gear if you are planning on towing often, want best performance, or want to run up to a 33" tire. Will yield great performance, but will get the worst gas mileage out of the OEM gear set.

 

 

^^ Sort of generalized, and a lot has to do with personal preference... but should at least get you in the ballpark of what each gear is good for.

[jrod332]

Thanks for all the info. Big help.

[WilliamBos]

AS stated check your glove box for RPO codes.

 

Here are a few in this post:

 

http://www.gm-trucks.com/forums/index.php?...st&p=391538

 

Also there is a RPO decoder here.

 

Thank you.

[sab316]

Will 285/70/17 tires be a problem with a 3.42?

[Matt_]

Will 285/70/17 tires be a problem with a 3.42?

 

 

Not with the gearing in your 6L80E trans