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 Post subject: Rear gear ratio
PostPosted: Sun Jun 03, 2007 10:40 pm 
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2 BBL ''SuperSix''

Joined: Sun May 13, 2007 9:58 am
Posts: 15
Car Model:
I have a 75 plymouth valiant, and I want to swap the rear gear ratio. I want a little more torque while city driving, and I dont drive on the highway much. I think its a 2.76, and I want a 3.23. Is this a hard thing to do, what does it involve? and will it kill my gas mileage?


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 Post subject:
PostPosted: Mon Jun 04, 2007 12:34 am 
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EFI Slant 6

Joined: Thu Sep 14, 2006 7:54 pm
Posts: 347
Car Model:
What rear is in it now? The 3/23 gears would probably help the gas milage in town.

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 Post subject:
PostPosted: Mon Jun 04, 2007 8:40 am 
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2 BBL ''SuperSix''

Joined: Sun May 13, 2007 9:58 am
Posts: 15
Car Model:
I'm pretty sure that its 2.76, thats standard right? Where could I get a 3.23?


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 Post subject:
PostPosted: Tue Jun 05, 2007 7:36 am 
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Supercharged
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Joined: Mon Jan 15, 2007 5:05 pm
Posts: 3767
Location: Black Diamond, WA
Car Model:
What rear do you have? 7 1/4? - 8 3/4? etc. There are 4 different types.

My 74 Dart has an 8 3/4 2.76 Posi. I had Randy's Ring and Pinion set it up. My car had a 3.23 7 1/4. Mileage was 18 mpg average with the 3.23. With the 2.76 I am getting 22.5 mixed city and freeway.

If you want more torque, upgrade the exhaust. I just went to 2.25" single pipe from the stock 1.5". It made a huge difference in useable power. Both tires will break loose at the slightest aggressive acceleration. Before it was a slug. Don't get me wrong, getting another $100 rear-end from the junkyard is simple but I went through (3) in 5 years because of the twisty roads I drive on at 120 miles a day.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG


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 Post subject:
PostPosted: Tue Jun 05, 2007 7:53 am 
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Turbo EFI
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Joined: Sat Jun 19, 2004 8:01 pm
Posts: 1937
Location: Rhine, GA
Car Model:
With it being a 75 he probably has a 7 1/4 or 8 1/4. Easiest thing for you to do would be find another rear in a junkyard that has the ratio that you want. It is getting hard to find a shop that will set up rears properly. I have an 8 1/4 rear that I plan on getting rebuilt with 3.23 gears to replace the 2.76 rear I have under my Duster now. Even with the 2.76 gears highway mileage isn't all that great and around town it is not very lively, especially if you pull out and try to climb a hill.

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 Post subject:
PostPosted: Wed Jun 06, 2007 12:45 pm 
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Supercharged
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Joined: Mon Jan 15, 2007 5:05 pm
Posts: 3767
Location: Black Diamond, WA
Car Model:
Torque really kicks in a 2000 rpm, so for city driving you need to figure on at least achieving that rpm. So base your rear-end choice on that, plus the bigger 2.25" pipe really helps with response time going up hills. My car has lots of power pulling hills once I hit 2000 rpm with the 2.76 rear.
On the really steep hills in Seattle leave it in second gear, like on Queen Anne. You will easily be going over the speed limit at the top.
Every night on the way home on I-90 to Issaquah I start out at 35 mph at the Factoria underpass and easily hit 70 about half way up the hill. With a one barrel carb, the bigger exhaust makes a huge difference.

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG


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