Early 80's 8.75" to 8.5" Swap

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Old Oct 24, 2021 | 12:23 PM
  #1  
ChibiDuo's Avatar
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Early 80's 8.75" to 8.5" Swap

Hi all,

My '82 Custom Cruiser has the oddball 8.75" rear end used for only a few years in wagons and other heavy cars, and I was hoping to swap it out for an 8.5" 10-bolt since there's far more aftermarket support. Assuming I find one with coil spring mounts, would that be a direct bolt-in, or are the mounting points different between the two housing types?

Here is a photo of what's on the car as well as the ID chart out of the CSM:


Old Oct 24, 2021 | 06:08 PM
  #2  
olds 307 and 403's Avatar
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The mounting points will be the same. I believe the wagon rear is wider than the sedan version. Take some measurements of your current diff especially if the replacement is already pulled out of the vehicle.
Old Oct 25, 2021 | 06:22 AM
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The 1977-1996 B-body wagons use a different rear axle than do the sedans. Yes, the track width is wider. This is to allow a sheet of plywood to fit flat inside the inner fenderwells. The suspension arm pickup points are also different. For example, the sedan rear sway bar will not fit the wagon without spacers.
Old Oct 25, 2021 | 06:29 AM
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You can get a chevy or buick wagon rear from a 1990 -1996 will bolt right in.
Does the drive shaft have a constant velocity knuckle buster joint or a regular single u-joint in the back to the rear?
Be sure you are correct about the width.
measurement from center to center of the spring perch mounts AND measure the lower control arm width on each rear making sure they match. Best to take your measurement on the existing rear before hunting this way your not wasting time cutting out something that does not work.
Generally 1977 - 1996 wagon rear will all interchange. WAGON rear.
Old Oct 25, 2021 | 08:28 AM
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Thanks for the info everyone. I’m just working with a single u-joint on either end of the driveshaft. Time to get the measurements off my rear end and start hunting the yards for roadmaster estates.
Old Oct 26, 2021 | 10:34 AM
  #6  
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Yah and you will likely get disc brakes too.
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