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  #1  
Old 06-22-2002, 02:37 AM
goodoleboy goodoleboy is offline
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Default 7 1/4 ,, 8 1/4????

okay i know the 8 3/4 rears good , but as for the 8 1/4s i need some advice. how do u tell if it is a 8 1/4 or a 71/4, and how easy is it to swap gears in a 8 1/4???? thanx
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Old 06-22-2002, 08:21 AM
jimmycarter jimmycarter is offline
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an 8.25 has 10 bolts on the cover, a 7.25 has 9 bolts.
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  #3  
Old 06-22-2002, 12:26 PM
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cuda66273 cuda66273 is offline
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7.25 has 2.5" axle tubes
8.25 has 3" axle tubes

The 7.25 is an excellent rear end for small garden tractors and other Briggs powered equipment, the 8.25 is good up to 350 HP after that your running on the edge. We ran a 8.25 with 3.91 gears for a year....always wondering if it would make just one more pass....it did but occasionally the posi unit wouldn't lock both tires and it would blow one tire off on the launch.

No longer a problem with the Dana 60 4.56 spool combination.

I sold the rear end to a fellow here and he put it into a 68 Cuda with a street version 318, he loves it!

When you get your 8.25, whoever tries to put the 3.91's in it will tell you it won't fit.....tell him to get the grinder out and cut the pinion to fit...it'll go, it just takes some inginuity....the common 2.72 ratio 8.25's have a smaller case and won't accept the thicker 3.91 gears...unless your determined like us
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Old 06-22-2002, 10:23 PM
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MY340 MY340 is offline
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Gear changes aren't as easy with the 8 1/4 as they are with the 8 3/4 rearends so decide on what gear will be best with your combo the first time. I have 4.10 gears in my factory 8 1/4 rearend which they went to in 1973 Duster340's. The outer edge of one ring gear tooth had to be ground alittle for the cross pin to clear during installation because of the thicker ring gear. MP use to sell a special notched pin but I don't think it's available anymore. People say 350-400hp is their limit. If your car will see alot of strip time the 8 3/4 may be better for peace of mind.
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Old 06-23-2002, 09:59 AM
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dirty dan dirty dan is offline
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Default rear end

Idon`t know what body you have but if you are playing with a duster go to the bone yard and get a B-body 8 3/4 . it will bolt right in and you will be much happier down the road
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Old 06-24-2002, 04:54 AM
goodoleboy goodoleboy is offline
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the bodys i am working with are a 69 dart and 70 dart swinger so tire clearance is an issue here, dont want 50 series but 60s would be nice, thanx for the help guys
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