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Old 07-25-2003, 10:06 PM   #1
brad20653
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Rear swap help

Can someone give me step by step maybe pictures on swapping my rear gears for 3:73's its a 72 chevy longbed 1/2 ton
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Old 07-26-2003, 08:15 AM   #2
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Old 07-26-2003, 02:30 PM   #3
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Old 07-26-2003, 03:06 PM   #4
70c10
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Brad , what are your current gears?. Are they 3:07's. If so, you will need a 4 series carrier to accomodate 3:73's.
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Old 07-26-2003, 03:48 PM   #5
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i dont know what they are
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Old 07-26-2003, 05:55 PM   #6
68_c10_on20s
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gears

my best advise is do what i did take it to a shop it will cost about 800 for a new posi and gear and seals and carriers but its worth it its a pain in the azz to do....
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Old 07-26-2003, 06:07 PM   #7
lukecp
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You need to find out what gear ratio you have right now....do you have a tach? If so, what RPM is your engine turning at various speeds?

If you do have 3.07's, and want to swap to 3.73's the cheapest way to do it would be to go pick up a used rear axle that already has 3.73 gears from a salvage yard. The rear axle will proably cost less then just a new set of 3.73 gears alone. You can bolt it in yourself, or take it somewhere to get it done.
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Old 07-26-2003, 08:06 PM   #8
brad20653
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no tach
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Old 07-26-2003, 09:12 PM   #9
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i measured my rearend by lifting the rear end and turning the tire. then count the number of rotations of the driveshaft for one full turn of the rear tire.

my gears are 3.73, and here is how i found that out:

1 turn of rear tire = 1-7/8 turn of driveshaft (or 1.875 turns)

2 wheels x 1-7/8 = 3.75 (which is approx 3.73)

this estimate is enough to give you a good idea of your current ratio.

if you cannot get it this way, or you prefer a more exact approach, you can open up the rear end and read the exact ratio off of the main gear (i believe it is marked on the face of the ring gear).
it cant hurt to open up the rear and replace the old diff fluid (which probably could stand to be replaced if it hasnt been replaced in its 30-year lifetime)

good luck!
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Old 07-27-2003, 09:07 AM   #10
Low69CST
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I've got some open carriers with 3.73's. If you'd be interested in one let me know, they would need to be gone through though.
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