corey
New Member
Posts: 14
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Post by corey on Apr 4, 2015 0:53:35 GMT -5
I have a question, and not being sure or knowing enough about this yet, I wanted to ask you guys.
I bought my '73 about a year ago and have had it in the shop having some things done. In regards to the rear end. It is an 8 3/4 (and having spoken previously with the original owner, he drag raced the car only) so the gears in this rear end are tall...if I remember correctly I was told 311. My mechanic said it was running about 3,000 RPM's at around 35 MPH.
I have no intentions of drag racing this car, instead cruising around town 99% of the time with maybe some rare highway driving. Given that, what shorter gear ratio would work well? Additionally, will I do any harm running these taller gears in the mean time if I do drive it around before switching out to shorter gears? Car is an Auto, 440 Magnum with a 727 trans. 205/70/14 tires on the front and 274/60/15 on the back.
Any help, advice or direction would be incredibly appreciated.
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Post by 1ol74charger4me on Apr 4, 2015 10:42:38 GMT -5
Probably have 4:11's. Great for awhile screaming around town, but unless you are a real diehard, the screaming engine will get to you on the highway and you will probably want a higher gear. Something like a 3:55. Before you buy something, find out which center you have. It will have 741, 742,or 489 on the side of it. Dr. Diff has some great deals on gears and whatever you need to put it together. Some guys will swap out the center and try and sell the old one together but a 4:11 is not very desirable so just plan on selling the gearsset when you pull it out. The only harm you may do with these gears in it, is increased engine wear and short tire life over a long span of time. Just to clarify, tall gears is usually the expression for lower numbers like 2:74, 2:94 and lower gears is usually the expression for numbers like what you have.
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corey
New Member
Posts: 14
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Post by corey on Apr 4, 2015 14:31:02 GMT -5
Probably have 4:11's. Great for awhile screaming around town, but unless you are a real diehard, the screaming engine will get to you on the highway and you will probably want a higher gear. Something like a 3:55. Before you buy something, find out which center you have. It will have 741, 742,or 489 on the side of it. Dr. Diff has some great deals on gears and whatever you need to put it together. Some guys will swap out the center and try and sell the old one together but a 4:11 is not very desirable so just plan on selling the gearsset when you pull it out. The only harm you may do with these gears in it, is increased engine wear and short tire life over a long span of time. Just to clarify, tall gears is usually the expression for lower numbers like 2:74, 2:94 and lower gears is usually the expression for numbers like what you have. Thank you. That helps immensly. Still trying to understand better the "short", "tall", "lower" terminology and how it applies to the gearing. I know he told me the gears were too tall and not the best for cruising or in town driving. You could do it of course, but the RPM's would be high. I'll do some googling to get a better idea of gear ratio terminology. I'm sure someone out there has broken this down. I took a look at Dr. Diff's website also. Thankfully it doesn't seem to be as expensive as I feared. I honestly don't think I am qualified to swap these out tho lol. I may hold off for a while and get it back to a shop and have them do it for me. I can work on some other things in the meantime.
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DynoDave
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Motown Mopar-Wizard
Posts: 11,140
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Post by DynoDave on Apr 4, 2015 15:33:00 GMT -5
You have lots of options. 2.76:1. 2.94:1, 3.23:1, 3.55:1, 3,73:1, or the 4.10:1s you have now. Those 4.10s will be a hoot coming out of the hole. You'll feel like a real street racing hero, able to light 'em up at will, and absolutely LEAP away from a corner (if you can get traction). But as mentioned, it's really a racing gear (or for a hard working, heavily loaded truck). You would likely grow very tired of the extra engine noise/stress in regular use, not to mention the extreme fuel consumption. But you need to think about how YOU want to use the car. Will it be 95% in town, cruising, club events, shows, etc? Or do you plan some serious highway touring, and long distance drives? Or maybe somewhere in the middle? To MY way of thinking (and this is just personal opinion), if you are making ALL highway runs, love a lot of top end speed and lower rpms at highway cruising speeds, think something sub-3....the 2.76:1 or 2.94:1. The "average" all around cruiser, 3.23:1 or 3.55:1. Sporty around town without killing you on the jighway. Just have to be the fastest away from a light on the street, or the qucikest 60' time at the track? Get the 3.73:1, or keep the 4.10:1.
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corey
New Member
Posts: 14
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Post by corey on Apr 4, 2015 15:49:25 GMT -5
You have lots of options. 2.76:1. 2.94:1, 3.23:1, 3.55:1, 3,73:1, or the 4.10:1s you have now. Those 4.10s will be a hoot coming out of the hole. You'll feel like a real street racing hero, able to light 'em up at will, and absolutely LEAP away from a corner (if you can get traction). But as mentioned, it's really a racing gear (or for a hard working, heavily loaded truck). You would likely grow very tired of the extra engine noise/stress in regular use, not to mention the extreme fuel consumption. But you need to think about how YOU want to use the car. Will it be 95% in town, cruising, club events, shows, etc? Or do you plan some serious highway touring, and long distance drives? Or maybe somewhere in the middle? To MY way of thinking (and this is just personal opinion), if you are making ALL highway runs, love a lot of top end speed and lower rpms at highway cruising speeds, think something sub-3....the 2.76:1 or 2.94:1. The "average" all around cruiser, 3.23:1 or 3.55:1. Sporty around town without killing you on the jighway. Just have to be the fastest away from a light on the street, or the qucikest 60' time at the track? Get the 3.73:1, or keep the 4.10:1.
"The "average" all around cruiser, 3.23:1 or 3.55:1. Sporty around town without killing you on the jighway."
I think this is the best for me. This is spot on to a message I received as well as what 1ol72charger4me recommended. 95% or more will be around town driving. A car show or two occasionally. I of course love the get up and go it currently has, however as you mention the noise and wear and tear is not what I want.
I'm glad I asked. Got some great advice I can put to use. Sincerely appreciate the responses as I was kinda in the dark as to which way to go.
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DynoDave
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Motown Mopar-Wizard
Posts: 11,140
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Post by DynoDave on Apr 4, 2015 20:52:21 GMT -5
The "average" all around cruiser, 3.23:1 or 3.55:1. Sporty around town without killing you on the jighway. It would have been better advice without the typo, but that's what you get sometimes when you type with 2 fingers.
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Post by 1ol74charger4me on Apr 5, 2015 0:44:57 GMT -5
I've been thinking about it all afternoon and I am pretty sure that gear terminology came from prewar cars having lower horsepower engines that were more reliant upon gear multiplication to create the torque necessary to move heavy loads. At that time one would gear the automobile with either a "high numerical" gearset for low speeds and a "low numerical" gearset for high speeds. I believe that got shortened to be "low" and "high" gears with the numerical values retained.
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Post by Nacho-RT74 on Apr 5, 2015 10:48:07 GMT -5
I had 3.23 open and went to 3:55 SG... I'm happy with it. Can notice the diff without kill the RPMs
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gip63
Forum Regular
Posts: 257
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Post by gip63 on Apr 6, 2015 20:35:34 GMT -5
I have 2.94's and takeoff ain't great but on the highway you need your pilots lisence cause it will fly. With a 440 and 2.94's there is no way I would try to find top end in a car that old . I don't hot rod mine I just like to cruse and my gears are good for that.
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Post by azhighcountry on Apr 17, 2015 13:35:41 GMT -5
I went with 3.55 in my 72 w/440. Good compromise gear. It is running about 3500 rpm at 65 so not terrible on the highway and still plenty of fun off the line. I have lots of engine so it will light em up from a rolling start and still gets a whopping 3 mpg.
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