70chev Posted October 23, 2011 Share Posted October 23, 2011 Here is my info: ENIGINE Chevy 355 9:1 compression Camelback heads My cam peaks out at 3200 RPMS TRANSMISSION Turbo 350 Mild shift kit Summit stall converter 1800-2100 RPMS TIRES 215-70-15 Currently I have 256 gears in it, and it takes a while to get the car moving. What would be my best bet when changing the gear size? I do drive on the freeway, and I would like to keep the gas mileage decent. What are your suggested gear sizes? Wayne Quote Link to comment Share on other sites More sharing options...
zmanabba Posted October 23, 2011 Share Posted October 23, 2011 2.73's would be the lowest you can go with that carrier. Not sure how much difference they would be. The lowest you would want to go with a lot of highway driving would be mid 3 series i.e. 3.42. You would also need to change the carrier-which would be a great time to upgrade to a posi. David Quote Link to comment Share on other sites More sharing options...
502ci Posted October 23, 2011 Share Posted October 23, 2011 2.73's would be the lowest you can go with that carrier. Not sure how much difference they would be. The lowest you would want to go with a lot of highway driving would be mid 3 series i.e. 3.42. You would also need to change the carrier-which would be a great time to upgrade to a posi. David That would be my suggestion also, matter of fact that is the gear I will be looking at swapping to in the futre. You mention "highway driving" and without an overdrive tranny and your tire diameter that would be a pretty ideal gear. At the very most a 3.55 gear...anything more and you will be looking to purchase an overdrive tranny or finding yourself not driving the car as much because of the gas prices... Quote Link to comment Share on other sites More sharing options...
Sam (Bones) Posted October 23, 2011 Share Posted October 23, 2011 a 3.08 ratio would work good too Quote Link to comment Share on other sites More sharing options...
Dans '70 Z20 Posted October 23, 2011 Share Posted October 23, 2011 I say anything over 3. 3:08, 3:23, 3:31, 3:42 max. Anything higher and you will regret it on the highway. The 3:31 gear is not available aftermarket b/c it was an original ratio offered by GM and the highest offered for our cars I believe. I saw you live in Minnesota and probably a lot of highway driving. I would likely shoot for 3:08 or 3:23 for better highway manners. Ultimately, it is what your goal is with the car. If the plan is eventually to get a 4 speed tranny, I would hold off making a gear change now, b/c if you do you would likely choose 3:73 or higher. If you have no intention of doing so, but looking to wake the car up a bit while keeping highway driving acceptable throw a 3:08 to 3:31 gear in rear and add a slight stall converter to your tranny. (Note: stall must be designed to match the power band of your cam). Stall converters nowadays are so tight you really don't feel 'em until your all in. Quote Link to comment Share on other sites More sharing options...
dbreese Posted October 24, 2011 Share Posted October 24, 2011 5.13's...... J/K 8.2 go with some 3.36's 8.5 or 12 bolt 3.31 or .42's David Quote Link to comment Share on other sites More sharing options...
Chevyss Posted October 27, 2011 Share Posted October 27, 2011 4.88s would be good. Quote Link to comment Share on other sites More sharing options...
680HPStroker Posted November 1, 2011 Share Posted November 1, 2011 A series 3 Eaton carrier and a set of 3.42's and call it a day. It gives you room to grow a little down the road. Quote Link to comment Share on other sites More sharing options...
Mike 57 Posted November 1, 2011 Share Posted November 1, 2011 I agree with the 3.42 Quote Link to comment Share on other sites More sharing options...
Ian Posted November 1, 2011 Share Posted November 1, 2011 I also suggest the 3.42 gears. I bought them knowing I was going to put a overdrive transmission in one of these days, but even with the stock TH400 and 402 big block on the highway at 70+ it is not too bad... Around town it woke the car up! Quote Link to comment Share on other sites More sharing options...
Dans '70 Z20 Posted November 1, 2011 Share Posted November 1, 2011 Jims70 has 3:42's in his 72 Monte w/454 and has no problems traveling to the cruises here on Long Island no matter the distance. Looks like 3:42's it is !!! Dan Quote Link to comment Share on other sites More sharing options...
Phil Posted November 3, 2011 Share Posted November 3, 2011 I'm happy with my 3.42's Quote Link to comment Share on other sites More sharing options...
Blue502 Posted November 11, 2011 Share Posted November 11, 2011 I think you will like the 3:42s.They will make a big difference.If you find they are too much on the highway,then you could go to a taller rear tire.If you ever upgrade to a 4 speed auto then it will be like going to 4:56 for acceleration and will cruise real nicely on the highway.With a lockup converter it will get noticeably better MPG. Quote Link to comment Share on other sites More sharing options...
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