Gear ratio check
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Most later model vehicles will have an RPO sticker somewhere in the vehicle. Some common places are under the trunk lid, in the glovebox, or in the console. | Most later model vehicles will have an RPO sticker somewhere in the vehicle. Some common places are under the trunk lid, in the glovebox, or in the console. | ||
| − | Look for codes having | + | Look for codes having "F", "G" or "H" prefixes. More codes '''[http://www.crankshaftcoalition.com/wiki/GM_RPO_build_codes#MORE_RPO_CODES: here]'''. |
===Axle codes=== | ===Axle codes=== | ||
| − | GM axles are stamped on the axle tube with codes for the year and ratio. Sometimes the casting numbers can also be used to show whether an axle housing is a limited slip differential (LSD) or not. | + | GM axles are stamped on the axle tube (and sometimes the center section) with codes for the year and ratio. Sometimes the casting numbers can also be used to show whether an axle housing is a limited slip differential (LSD) or not. |
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| + | Some sites with ratio and axle code info are: | ||
| + | *[http://www.novaresource.org/axle.htm Axle Codes] from novaresource.org | ||
| + | *[http://www.thecamaro.com/Decoding/Chevy-Axle-Rear-End-Decoding/ Chevrolet Rear Axle Code Identification and Decoding] from thecamaro.com | ||
| + | *[http://www.thecamaro.com/Decoding/Chevy-Axle-Rear-End-Decoding/Chevy-Full-Size-Rear-Axle-Codes.php Chevrolet Full Size and Impala Rear End/Axle Assembly Codes] from from thecamaro.com | ||
| + | *[http://aplsweb.com/Topics/Differential.htm Various tid-bits, et cetera] from aplsweb.com | ||
| + | *[http://tech.oldsgmail.com/axle_useage.php GM A-body codes] from tech.oldsgmail.com | ||
| + | *[http://www.gnttype.org/numbers/axcodes.html Gear ratio info] from gnttype.org | ||
Ford rear ends sometimes had tags under one of the carrier bolts that had the ratio and a code for being a LSD or not. Ford also used an axle code on the body tag on some models. | Ford rear ends sometimes had tags under one of the carrier bolts that had the ratio and a code for being a LSD or not. Ford also used an axle code on the body tag on some models. | ||
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This is much easier with 2 or 3 people. | This is much easier with 2 or 3 people. | ||
| − | == | + | ==Other methods== |
| − | + | ===First method:=== | |
'''1.''' Drive the vehicle at a steady speed. Note the RPM. | '''1.''' Drive the vehicle at a steady speed. Note the RPM. | ||
::For example, if the vehicle is driven at 50 mph, and at that speed the tachometer reads 2,000 RPM, record that the engine speed was 2,000 RPM at 50 mph. | ::For example, if the vehicle is driven at 50 mph, and at that speed the tachometer reads 2,000 RPM, record that the engine speed was 2,000 RPM at 50 mph. | ||
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60,000 / 16,800= 3.57 or 3.57:1 gear ratio. | 60,000 / 16,800= 3.57 or 3.57:1 gear ratio. | ||
| − | + | ===Second method:=== | |
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Another easy way to estimate the final drive ratio is to use a [http://ctny.audiworld.com/mark/s4/gears/gear_calc.html gear ratio calculator]. | Another easy way to estimate the final drive ratio is to use a [http://ctny.audiworld.com/mark/s4/gears/gear_calc.html gear ratio calculator]. | ||
| − | Drive the vehicle at 50 MPH (as an example), note and enter the speed (50 mph), the RPM | + | Drive the vehicle at 50 MPH (as an example), note and enter the speed (50 mph), the RPM that was seen, and for the final drive enter '''1''' into the calculator. When you hit calculate, the rear gear ratio estimate will be the result. |
==Resources== | ==Resources== | ||
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