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Complete Rear bushing and 3.91 gear swap DIY
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04-22-2013, 08:48 AM
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jeremywes
Drives: 2012 Camaro SS
Join Date: Aug 2012
Location: Houston, TX
Posts: 504
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3.91 Gear swap
On to the 3.91 gear swap.
I was impressed by this little cordless impact gun. It handled 90% of the work, however I did have to use a more powerful corded impact gun for some of the heavy lifting
This puller was too small so I had to open it up with a grinder but I was able to make it work. a 3 arm puller would have worked better.
Here is a picture after the yoke is removed
Next I marked the bearing caps left and right with a small chisel
Here you can see that I have layed everything out exactly how it came out of the housing so I can ensure it goes back in the same way.
To remove the pinion I hammered it over a piece of wood so it had something to fall on.
Here is the pinion removed from the housing
Next remove the bolts that attach the ring.
NOTE: These are reverse thread bolts (lefty tighty, Righty Loosey)
Once the bolts have been removed tap the ring off, I had to gently pry to get it started. Again I used a piece of wood so it could fall safely
I placed the carrier in the freezer and the ring on a propane BBQ. They went together very easily after that. Otherwise they would need to be pressed on.
Next using the new bolts from the GM kit I attached the ring
I removed and reused the old pinion bearing using a friends press. I would have just used a new one but the car only has 3k miles on it and the local dealer didn't carry it in stock.
Now same operation for the pinion bearing.
Here you can see the old pinion, shim, bearing, crush sleeve. Make sure it goes back on the pinion the exact same way.
Here is the old crush sleeve compared to the new one
I made a little tool out of 2" PVC pipe to tap the bearing on. It didn't take much pressure to tap it on once the pinion had been in the freezer and the bearing was heated.
Next CLEAN the pinion yoke by scraping all of the white factory paste out of the splines. Grease the inner bearing and crush sleeve to make sure it doesn't bind when you begin re-assembly.
Here I am using a pry bar and two of the yoke bolts to get some leverage as I tighten the pinion nut down to crush the pinion crush sleeve. Here is where a strong impact gun will come in handy
This is the tricky part. Tighten the pinion nut until you achieve 18 - 25 inch pounds of rotational torque. Work in slow bursts and take your time because you can't un-crush if you go past the torque range of bearing preload.
Once you have the proper rotational torque pin the pinion nut by punching it into the pinion recess
Now insert the carrier into the housing keeping all of the bearing races and shims on the same sides that they came from.
Here I used a 2x4 to tap the left side shim into place.
Now install the bearing caps and torque to spec. I used 77ftlbs
NOTE: GM makes 3 different rear ends so make sure you know what you have. I am installing this into a 2012 SS with the 218mm axles
Remember to use anti-seize anytime a steel bolt goes into an aluminum housing
Here are some GM spec that a friend printed out for me
I made a steel plate so I could get the magnetic base dial indicator to attach to the housing.
Here is the zeroed dial indicator
Here the backlash is .003" GM spec is .002 - .005
Here you can see the pattern on the DRIVE side of the ring gear teeth
Here you can see the pattern on the COAST side of the ring gear teeth
Next reinstall the case cover. I used 55lbft
Remember to use anti-seize anytime a steel bolt goes into an aluminum housing
Remember the gear lube
WITH
a friction modifier
Here are some GM specs
Here is where you can see what rear end your car has. You can see mine is a 218mm axle
Last edited by jeremywes; 04-22-2013 at
08:54 AM
. Reason: Text edit
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