1967 - 1972 F-100 & Larger F-Series Trucks Discuss the Bumpsides Ford Truck

Quick and easy diff swap. Is it possible?

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Old 05-17-2016, 11:49 AM
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Quick and easy diff swap. Is it possible?

I want to swap out the pumpkin on my 9 inch rear for better highway speeds.
My buddy has offered me his driveway since I don't have any room at home right now. What parts should I have ready to go so the job doesn't go into the next day. Any special tools needed? I've never done this job before and I don't want to do it again!
Thanks for the tips in advance.
 
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Old 05-17-2016, 12:31 PM
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Lift the back of the truck, remove the wheels and remove the drums. You'll need a 3/4" socket to take the 4 nuts loose on each side on the backing plate, where the stamped steel axle retainer is bolted down.

Slide the axles out of the housing (all the way out of the housing), being careful not to let the weight of the axles drag across the seals. It's not good to pull the axles out just enough and leave them hanging out for clearance of the 3rd member to come out of the housing. The weight of the axles resting on the axle seals can damage the seals.

Once the axles are out, remove the drive shaft from the companion flange on the 3rd member. Take the (10) nuts loose on the 3rd member (will require a 9/16" socket and a 9/16" end wrench to get to the two extreme lower nuts on the 3rd member. IF the rear end has never been messed with before, there will be (10) copper crush washers on each of the (10) 3/8"-24 studs. These will have to be removed to be able to slide the 3rd member out of the housing. With all the nuts/crush washers removed, put a catch pan under the housing/3rd member and pull the 3rd member out.

To put it back together, simply reverse this process.

With the axles out, this is the prime time to install new axle bearings and seals.
 
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Old 05-17-2016, 12:36 PM
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Swapping a pumpkin takes less than an hour.
 
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Old 05-17-2016, 12:53 PM
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When you pull the axles, verify the spline count is the same as the new setup before pulling the third member.
 
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Old 05-17-2016, 01:25 PM
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A trick I do for the copper washers is to use a screw driver and tap them from their edge counter clockwise to more less unscrew them off.
 
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Old 05-17-2016, 02:10 PM
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Originally Posted by HIO Silver
Swapping a pumpkin takes less than an hour.
5 hours later.....
 
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Old 05-17-2016, 02:46 PM
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Originally Posted by 351Cleveland C4
5 hours later.....
Hah! Murphy's Law! That's what I'm trying to avoid.
Thanks allot for all the great tips.
1) confirm the spline count before going any further.
2) get new washers
3) have black RTV ready (not the old dried out tube)
I know it would be a good time for bearings and seals but unless there is an obvious problem I will be leaving them alone for now.
I'll be reporting back on the progress.
Hoping it will be a short post!
 
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Old 05-18-2016, 10:30 AM
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It's a 2 hour job for me, but I drink a lot....
 
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Old 06-02-2016, 06:55 PM
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Just as I suspected. An easy swap is not possible and now my truck is blocking the driveway and the garage so my wife can't park her car
The U bolts needed to attach the driveshaft universal joint to the diff are different than the ones that came off my truck .
The ones needed on the new diff are smaller (the holes closer together).
The u Joint fits in the cradles properly but the holes are spaced closer together.
Oh, and to add to my frustration:
After I mounted the diff I discover there are no fittings to re fill with fluid
How am I supposed to fill this pig? Through the axle ends at the brakes?
I knew I should have just left everything alone
 
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Old 06-02-2016, 08:07 PM
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Update, Thanks to my friendly driveshaft machine shop I now have the proper u bolts and universal joint to make it work.
How much fluid do I pump down the axle shafts?
Thanks
 
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Old 06-02-2016, 09:10 PM
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Your sure you didn't overlook a plug? They're on the driver side. It could be a flush mount type thing.
 
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Old 06-02-2016, 09:16 PM
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Originally Posted by 68fish
Update, Thanks to my friendly driveshaft machine shop I now have the proper u bolts and universal joint to make it work.
How much fluid do I pump down the axle shafts?
Thanks
The 9-inch rear end requires 5 pints of gear oil. 2 and a half bottles so, you'll need 3 bottles of gear oil.
 
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Old 06-03-2016, 12:39 AM
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Originally Posted by ultraranger
The 9-inch rear end requires 5 pints of gear oil. 2 and a half bottles so, you'll need 3 bottles of gear oil.
Thanks, I'll fill it through the vent.
No fittings on the diff.
 
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Old 06-03-2016, 12:54 AM
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What kind of case is it? Every ford factory case had a fill plug.
 
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Old 06-03-2016, 01:36 AM
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I dunno.
I'll take a pic tomorrow.
Definitely no plug.
The yoke uses a later 1 1/8 size universal.
My U bolts were smaller, not bigger.
It's been a bad week so I thought I would punish myself more by doing the swap.
 

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