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| | | | Joined: Feb 2007 Posts: 56 'Bolter | | 'Bolter Joined: Feb 2007 Posts: 56 | Hi all, Grant here from Wisconsin. Looking for experienced opinions for my 59 3100. I currently have a 330 hp small block with a Saginaw 4 gear from early 70's car. I am running 255-70x15 tires. I currently run 2500 rpm at 55 mph using factory rear end, gear ratio not sure of. It was a 6 cylinder 3 speed.(3:90/4:11?) I have a 12 bolt posi with 3:73 ratio that I intend to install in truck. I would like to get the rpm's down some more for highway travel, and still have good performance. (occasional burnouts). What do you think, leave the 3:73 or switch to 3:42? Thanks, Grant. | | | | | Joined: Feb 2004 Posts: 29,844 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,844 | I'd stay with the 3.73. It will give you a decent hole shot, without being too rough on cruising RPM or gas mileage. Be sure you have some way to limit the spring windup if you're going to do burnouts. Getting a tire hooked up after the spinning softens the rubber will make a pretzel out of a spring.
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: Jul 2008 Posts: 413 Shop Shark | | Shop Shark Joined: Jul 2008 Posts: 413 | The 3.73 & the 3.42 are perfect for what you are looking for.The 3.42's really arent that much different from the 3.73's.
They are so close, you wont notice the difference.
Keep the 3.73 since you allready have them.
Jeff | | | | | Joined: May 2005 Posts: 8,878 . | | . Joined: May 2005 Posts: 8,878 | Don't have any recommendations, but this calculator will let you see the RPM difference between the two so you can compare: http://www.onlineconversion.com/bigger_tires.htmGrigg | | | | | Joined: Mar 2007 Posts: 4,215 Moderator | | Moderator Joined: Mar 2007 Posts: 4,215 | I hope the Saginaw will stand up to 330 horses. I used to have a 72 Nova SS 350 and put in a 4 speed Saginaw. It came out of a Vega and lasted a few months. The next tranny also lasted a few months. | | | | | Joined: Jun 2004 Posts: 8,597 Riding in the Passing Lane | | Riding in the Passing Lane Joined: Jun 2004 Posts: 8,597 | I vote for the 3.42. Anything lower is not practical or comfortable for highway driving.
They say money can't buy happiness. It can buy old Chevy trucks though. Same thing. 1972 Chevy c10 Cheyenne SuperIn the Gallery Forum | | | | | Joined: Oct 2006 Posts: 4,983 Master Gabster | | Master Gabster Joined: Oct 2006 Posts: 4,983 | I vote for the 3.42. Anything lower is not practical or comfortable for highway driving. I agree with that. You want to cruise at 70mph with your rpms at or under 2000. That will give you the better gas mileage.
~Jim
| | | | | Joined: Dec 2004 Posts: 1,897 Shop Shark | | Shop Shark Joined: Dec 2004 Posts: 1,897 | The stock 3.90 geared rear end is plenty strong behind a v8. I believe I would change transmissions before I would change the rear end. A 3.90 rear end with a .73 overdrive will give tou an effevtive rear end ratio of 2.85:1. At 55 mph rpm will drop from 2476 to 1808. If you are changing the stock rear end because you want positraction, then that is a different story. I would go with the 3.73 gears you have, and still try to find an Overdrive transmission that can take that type of HP... like an A833 4 speed, or a tremic 5 speed. | | | | | Joined: Feb 2007 Posts: 56 'Bolter | | 'Bolter Joined: Feb 2007 Posts: 56 | Hello again, and thanks for the replies.. I am getting ready to tear into it for inspection and assessment. I welcome more feedback. Thanks, Grant. | | | | | Joined: Jul 2005 Posts: 2,031 Shop Shark | | Shop Shark Joined: Jul 2005 Posts: 2,031 | really when you look at the stats there ain't much difference twix the 2 i'd stay w/ the 3.4 w/ a four speed the 3.7 w/ a 5 speed U-try it http://vexer.com/68rt/speed.html
Last edited by carolines truck; 12/30/2008 3:12 AM.
Jim & Caroline
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Gooday-that's my 1¢ answer due to the lousy economy ~ cause I ain't got - no . mo . doe
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