FullMonte Posted June 28, 2004 Share Posted June 28, 2004 Funny thing about education... the more I learn, often, the more confused I get. Case in point: I've finished about all I will do with engine upgrade (new manifold, headers, 600 CFM carb and mild cam) and now ready to upgrade the rear end, but not sure which way to go. I have the 350 with regular transmission (300?). Not sure what the gears were/are, but I know it is not a posi. My goal is to make the car less of a highway cruiser and more of a "neighborhood bruiser." I seldom drive it over 20 miles at a time. Trouble is I don't know the first thing about the ratios that I should get. I hear everthing from 2:73 to 4:11. What were these cars equipped with in the first place, and what do you recommend for an upgrade to make it jump while still being capable of driving on the highway without winding it up too much. Also, is it possible to add a posi (this is a 10-bolt) or should I try to find happiness with one wheel? Thanks! George Quote Link to comment Share on other sites More sharing options...
Grease Posted June 29, 2004 Share Posted June 29, 2004 George ... regular transmission (300), thats most likely a TurboHydromatic 350 . the most common gear ratio i have come across with the 350/350 combination is 2.73:1 yes you can add a posi when upgrading your rear axle gears. for neiborhood bashing i would consider 3.55:1 or 3.73:1 they are available also as i recall in 3.23:1 and 3.42:1 i believe you can find a RPM/ratio calculator at 700R4.com have fun mike Quote Link to comment Share on other sites More sharing options...
FullMonte Posted June 29, 2004 Author Share Posted June 29, 2004 Thanks for the info, Mike. I am thinking the 3.73 is what I will go with. More confusion... When I look in the Summit catalog, I see about four different references to GM 10-bolt 3.73 gears: 7.5/7.625", 27 spline pinion 8.20", B or P axle, 27 spline 8.20", 25 spline 8.50", 25 spline Is there a way to easily tell what I need? They also make a note regarding a 3.08 and lower carrier versus a 3.23 and higher carrier. What's that all about? Thanks! George Quote Link to comment Share on other sites More sharing options...
Guest Posted June 29, 2004 Share Posted June 29, 2004 it should be the 7.5 27 spline. Quote Link to comment Share on other sites More sharing options...
Guest Posted June 29, 2004 Share Posted June 29, 2004 George, check out www.Nationaldrivetrain.com go to differential gearing ring & pinion. They have a calculator to help find what gears are best for you. Depending on what gear ratio you go with it will let you know what series carrier you will need. (3.08 or lower or 3.23 or higher) or a thick gear will work too with your carrier.. You have to get a posi / power trax something, NO ONE WHEEL WONDER!! Check it out or give them a call. Matthew Quote Link to comment Share on other sites More sharing options...
FullMonte Posted June 29, 2004 Author Share Posted June 29, 2004 Any ideas on what I can expect to pay for the parts necessary to change to a posi and change gears at the same time? I am assuming everything will fit in the same housing. Quote Link to comment Share on other sites More sharing options...
Andreas Posted June 29, 2004 Share Posted June 29, 2004 Any ideas on what I can expect to pay for the parts necessary to change to a posi and change gears at the same time? I am assuming everything will fit in the same housing. Check this out: Posi Cost Thread Quote Link to comment Share on other sites More sharing options...
FullMonte Posted July 19, 2004 Author Share Posted July 19, 2004 Bringing this up again. Still trying to change the back end from the open to a limited slip or posi and better street gears. Is this a good deal? http://www.drivetrainsuperstores.com/store_detail.asp?id=59 Thanks! Quote Link to comment Share on other sites More sharing options...
Guest Posted July 21, 2004 Share Posted July 21, 2004 I have heard really good things about the Powertrax. I was going to get it untill I landed a rear end built for 350.00. There is no friction material like the posi unit. When your going in a straght line, it accts as a spool, equal power to both rear wheels. But acts as an open when going around corners. If this info is wrong, someone else please jump in. Also, make sure you know what rear end you have. My old 72 had a 12 bolt with a 2.73. My current one had a 8.5" 10 bolt. Also, I think the 3.73 gear is the best of both worlds without overdrive. Will get off the line, but you can still jump on the highway. here is a the address for the powertrax: Powertrax Quote Link to comment Share on other sites More sharing options...
Guest Posted July 21, 2004 Share Posted July 21, 2004 Powertrax is a new item that I have been reading about in the mags and I will definately do that on the next rearend that I build. Quote Link to comment Share on other sites More sharing options...
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