New gear size
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Teching In
Joined: Apr 2013
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New gear size Hey everybody I'm ordering some new 4:10 tonight and have a stupid question. I'm not sure if I need 7.5 inch or 7.625(99 z28 m6 series 3)? I'm not able to take it apart to measure so just wondering if there was an rpo code or something. Thanks for any info!
OEM gearsets of 2.73,3.08,3.23, & 3.42 for our late model f-bods are 7.625",and that's where the 7.625" designation ends. Everything else,carrier and other internal parts,are 7.5". All aftermarket gearsets are 7.5". You can't get a 4.10 set in 7.625". All 7.5" gearsets fit our cars.
The 7.625" gearset is larger by 1/8" at its' largest point(1/16" larger on the radius). As the f-bods increased in horsepower from the factory,GM determined that a 1/8" larger gear would fit in and be able to be used with all the existing parts. That 1/16" larger radius does make for a stronger set,BUT not by much. Aftermarket gear manufacturers are NOT gonna setup special tooling to make that gear 1/16" larger. Some aftermarket manufacturers have 2 lines of 7.5" gearsets. One for strength(and not as quiet) and one regular for normal quiet.
All of the 3.73s' that are popular for the automatics and 4.10s that are popular for the 6 speeds are 7.5".
The 7.625" gearset is larger by 1/8" at its' largest point(1/16" larger on the radius). As the f-bods increased in horsepower from the factory,GM determined that a 1/8" larger gear would fit in and be able to be used with all the existing parts. That 1/16" larger radius does make for a stronger set,BUT not by much. Aftermarket gear manufacturers are NOT gonna setup special tooling to make that gear 1/16" larger. Some aftermarket manufacturers have 2 lines of 7.5" gearsets. One for strength(and not as quiet) and one regular for normal quiet.
All of the 3.73s' that are popular for the automatics and 4.10s that are popular for the 6 speeds are 7.5".
Last edited by FirstYrLS1Z; Aug 3, 2013 at 08:12 AM.
