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Transmissions and drive-trains Troubleshoot, repair, rebuild.

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Old 04-25-2011, 05:28 PM   #1
gmarkie
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Default 77 rear axle question

Guys,
I have a 2.28 to 1 ratio rear axle (fleetwood frame) and I am trying to update it with another GM axle since I havent been able to locate a 3:08 ratio (anyone know where I can locate one by chance? interested in a posi as well). What I have noticed with other GM rear axles is the the upper control arm bushing mounts are shorter on the housing therefore I believe the control arms won't be long enough. What have others done to compensate for this? I would greatly your advice. Thanks,
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Old 04-25-2011, 06:43 PM   #2
Bruce Roe
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Default axle

You are trying to improve performance? You could instead change to a switch pitch version of your TH400 trans, and keep your fuel economy. My big car took 10% off 0-60 this way, kept my 2.41:1 axle. It would do 15s in the 1/4 miles that way, with just dual exhausts. Bruce Roe
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Old 04-26-2011, 06:01 AM   #3
Ted in Olympia WA
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The 8.5 out of the later caprice (up to early 90's) will bolt right in. You have to swap over the driveshaft flange. If you find an old cop car it should also have posi, but not all do.

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Old 05-07-2011, 11:37 AM   #4
gmarkie
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Found one... thanks for the help.
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Old 07-29-2011, 12:34 PM   #5
fleetwood472
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Hey Bruce,

Do you think the gears could be changed from 2.28 to 2.41 in the same carrier? I was thinking about swapping to that gearset since i'm running a switch pitch th400 in my 78 fleetwood. Thanks - Justin
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Old 07-29-2011, 06:34 PM   #6
Bruce Roe
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There were lots of 2.41 axles in big cars of that era, probably one for your car. I'm not familiar with that model, any chance is uses the same axle as a Buick or Olds, which frequently had that ratio? Bruce Roe
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Old 08-04-2011, 07:53 PM   #7
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I have a 78 caddy rear end in my 81 deville.. It is a posi and had 2.28 gears... I put in the lowest gears that fit that carrier without a spacer, that is 2.56 ratio..Its been quite a few years , but if I remember right I got the gears from Geno's { gears or rears , I don't remember} and I think he was in NY.. And I should have tried the 2.28's before I changed it....The switch pitch does make a big difference...
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