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| | | | Joined: Feb 2014 Posts: 19 'Bolter | | 'Bolter Joined: Feb 2014 Posts: 19 | Recently purchased another 50 chevy. The previous owner had a SM420 and a 10 bolt rear end with 2.73 gears professionally rebuilt.
I cant figure out this combination for the life of me.....just seems odd for a 250 I6 engine.
Obviously with a 7:01 first gear ratio the sm420 will push those gears just fine but does this make sense to anyone else?
I hate to just dump the transmission or the rear end but both seem odd choices. Any thoughts. | | | | | Joined: Feb 2004 Posts: 29,877 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,877 | The 250 will be a little hard-pressed to maintain highway speed, particularly on an upgrade with a gear that tall. Also, the non-synchronized 1st. gear will be all but useless in traffic, requiring a full stop to get it into gear without grinding, and a very quick over-rev if a 1-2 shift isn't made within a few feet of getting moving. Using 2nd. as a starting gear might require slipping the clutch a little. Even a 3.08 gear would be more likely to be user-friendly. The 2.73 was a popular option with big block engines like Olds, Cadillac, and Buick, with lots of low-end torque and an automatic transmission. Those engines could be run just above idle at highway speeds for better gas mileage. Not good with a stick shift and a low-torque engine!
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
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| | | | | Joined: Feb 2014 Posts: 19 'Bolter | | 'Bolter Joined: Feb 2014 Posts: 19 | Thats what I thought. I guess I will put the Muncie up for sale and possible re gear the 10 bolt. thanks | | | | | Joined: Nov 2006 Posts: 2,544 Shop Shark | | Shop Shark Joined: Nov 2006 Posts: 2,544 | If you change the rear end to something with a better gear ratio you may find that your sm420 works just fine. Unless you are going for a rear deep rear end ratio and then want a overdrive transmission. | | |
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