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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: eramirez198121 on January 26, 2009, 07:42:43 pm

Title: Gear Ratio
Post by: eramirez198121 on January 26, 2009, 07:42:43 pm

Hi guys hope all is well. I had a question can anyone help me understand what is meant when the phrase gear ratio is thrown around? Are they referring to the transmission, the time chain, or the differential?. ???

Title: Re: Gear Ratio
Post by: VileZambonie on January 26, 2009, 07:47:05 pm

Gear ratio referrs to the number of rotation 1 gear has to the one it is in mesh with. You can calculate gear ratio by dividing the driven gear by the drive gear. If someone is referring to the final drive ratio that is the last reduction in the driveline and in a RWD application this would be in the rear end. Differential gears are the gears that allow the axles to turn at different speeds.

Title: Re: Gear Ratio
Post by: eramirez198121 on January 26, 2009, 07:51:18 pm

What is a good gear ratio to have and does it give you more horsepower?

Title: Re: Gear Ratio
Post by: VileZambonie on January 26, 2009, 08:02:34 pm

I assume you mean final drive ratio? Give more info on your truck, what it is, tire size, intended usage. No it will not give you more HP just effects the torque multiplication factor.

Title: Re: Gear Ratio
Post by: eramirez198121 on January 26, 2009, 08:14:57 pm

It is a 1978 Chevy Truck it stock 350 engine it has an eldebrock intake and eldebrock cam with dyno max headers. Just wanted to give it more of a Boost. I am new to this and I rebuilt the engine myself it my very first one. I had fun putting it together. I have alway wanted to do one and I will be doing more here in the future. There nothing like being able to say I made that! Is it going to work I will soon find out. I do know that I reference many of books and also the Chilton manual as well.

Title: Re: Gear Ratio
Post by: VileZambonie on January 26, 2009, 08:18:34 pm

Quote

Give more info on your truck, what it is, tire size, intended usage

2 or 4wd?

tire size?

Transmission?

Title: Re: Gear Ratio
Post by: eramirez198121 on January 26, 2009, 08:23:45 pm

2wd 400 turbo transmission I am not sure what kind of tire I am going to go with any suggestion? The tire on it are donuts right now. I want to become more knowledgeable that is why I join this Forum it really informative.

Title: Re: Gear Ratio
Post by: VileZambonie on January 26, 2009, 08:56:17 pm

If you aer going to run a tall tire and not a lot of highway use 3.73:1

If you are going slightly lower profile and occasioanl highway 3.55:1

Title: Re: Gear Ratio
Post by: Captkaos on January 26, 2009, 09:28:40 pm

I have also used 3.42, it was pretty good on non overdrives.  My 454 ran better with them.