Rear End Gear swap

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Old 01-16-2017, 12:39 PM
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Rear End Gear swap

So I know I have talked about this before, I am running a 2:94 or 2:97 on my 68 Dodge Coronet 440, I am planning to swap it out when I get home from work towards the end of February 1st of March,
I am looking at 3:73s or 3:91s Now I found a guy that has a 3:91 Ring and Pinion set new or NOS never been used and I might be able to get it for $150. Now my buddy said I also need the 8-3/4 Master Bearing Set for the swap, I am running a 489 case housing.
What else would I need and what is your thoughts on my project, I am just going to tear into it and drink beer while I do it, I figure between You tube,Books, And you guys i can get it done.
Old 01-16-2017, 03:00 PM
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Kind of depends on How much Hwy? and How much City Driving? And What the compromise will be for the performance your looking for?

I Like a 3.91 for all around....
I like a 4.10 For hot Rodding
I like a 4.30 for racing...

Oh.. And Sure-Grip it for sure...

Last edited by RacerHog; 01-16-2017 at 03:15 PM.
Old 01-16-2017, 03:17 PM
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I'm a fan of 3.73s for a car that gets highway use and never hits the dragstrp, 3.91s if you have taller rear tires.
Old 01-16-2017, 03:34 PM
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ray -

I'm switching from 3.23s to 3.90's. I'll let you know how it goes in a month or so.
Since I do a bit of highway driving, the only reason I'm going ahead with the swap, is because there's a "fail safe", a viable over-drive unit on the market.

What I would do first is go through one of the gear ratio calculators and see what kind of rpm you'll be running at your normal driving speeds.

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Old 01-16-2017, 04:23 PM
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Originally Posted by RacerHog
Kind of depends on How much Hwy? and How much City Driving? And What the compromise will be for the performance your looking for?

I Like a 3.91 for all around....
I like a 4.10 For hot Rodding
I like a 4.30 for racing...

Oh.. And Sure-Grip it for sure...
I have driven 2 times to the next town over 35 miles, other than that its just sporting around are small town, And I mean small town 7k population.
I want something snappy.
I am just trying to figure out how mus=ch its going to cost me and what I will need.
Old 01-16-2017, 04:24 PM
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3:91 is what i am leaning to, I am also meeting with this one guy this weekend on aluminum heads.
Old 01-16-2017, 07:14 PM
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4.10s were the gears back in the day but so was thirty cents a gallon premium. I've run 4.10s with a fairly mild cam and gotten seven mpg on the highway and with a fairly wild cam you could watch the gas gauge move on the highway!
Old 01-16-2017, 08:02 PM
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Good.... 3.91's.... Good Choice.... Now just keep all the low end torque and you will be good to go...

Need some Pricing on the diff stuff.. >>>>> http://www.doctordiff.com/

Might help you pencil a price together>>>> http://www.mopartsracing.com/parts/dtrain.html

Lot out there to choose from...
Old 01-17-2017, 05:44 AM
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Originally Posted by RacerHog
Good.... 3.91's.... Good Choice.... Now just keep all the low end torque and you will be good to go...

Need some Pricing on the diff stuff.. >>>>> http://www.doctordiff.com/

Might help you pencil a price together>>>> http://www.mopartsracing.com/parts/dtrain.html

Lot out there to choose from...
Yea their is, I do not know where to start, I need to get with some one that will tell me what I need and I can just buy.
My wife said I can spend 5K on the car this spring and I want to use it wisely.
Old 01-17-2017, 06:00 AM
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Good morning guys, Its a good day and a little chilly here in PA, Should be talking to a Real estate person today that found a house with a 60X60 shop back home in Wyoming and heated...That would be my dream shop.
Anyways guys have a Blessed day.

Old 01-17-2017, 08:12 AM
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Originally Posted by raycan2
Yea their is, I do not know where to start, I need to get with some one that will tell me what I need and I can just buy.
My wife said I can spend 5K on the car this spring and I want to use it wisely.
Figure out how to spend 7K and tell her you spent 4.
Old 01-17-2017, 09:13 AM
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My wife teaches Math and does the books at the house, She would catch that pretty quick. With that being said she probley does that to me.
Old 01-17-2017, 01:47 PM
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I should be so lucky.....'
Old 01-17-2017, 04:37 PM
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I would get a full master kit for all new differential bearings.

I would get new ring gear bolts.

For a 489 definitely one of these http://www.doctordiff.com/8-3-4-489-...liminator.html
Old 01-17-2017, 05:41 PM
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Originally Posted by Coronet 500
I would get a full master kit for all new differential bearings.

I would get new ring gear bolts.

For a 489 definitely one of these http://www.doctordiff.com/8-3-4-489-...liminator.html
I did talk to them today and they have good prices, $330 for the whole set to get it done, I called CarQuest and it was $489 just for the Ring and Pinion.
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