Frozen DIff

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mdunlap

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My Car
It's a 1973 Convertible project.
IMG_5882.JPGIMG_5883.JPGHey Guys,

I'm rebuilding a 9" and want to put a diff in that isn't turning. It has light rust and debris. What is the best way to free this thing up without costing a bunch of money or causing me to have to align the gears again? Please remember that I'm broke and don't have a repair shop. :)

I'm trying to show photos but can't seem to get them to show when I preview this post.

 
You can soak it in old motor oil if you have some around but it might take a week or 2 of screwing with it before it might break free. Add that to the fact that it has a good chance of exploding upon regular use and I wouldn't do it without a rebuild.

 
I have freed a frozen engine block that looked equal with Evaporust by soaking it. Other products I tried along the way were Kroll, an equal mix of atf/mineral spirits, oil and then kerosene. Had the Evaporust not worked I was moving on to electrolysis (check the web for this process). In my case, I wanted the dated block and Hipo caps. It soaked just short of two weeks.

 
I would worry about rust on the loaded areas of the gear teeth. If you get it moving and cleaned out, it may not last long if enough of there's deep rust on the teeth...

 
Thanks guys! That is a lot of great info. I think I'll call about the hot tank. If it's too expensive i'll do the long soak and take it apart. I'd like to learn how to properly set a ring and pinion anyway. Even though the photos look like rust has eaten through, I sprayed some wd on the gears and they appear solid.

Sent from my iPhone using Tapatalk

 
Dump the whole unit in oxalic acid, perhaps? Should kill off the rust quite well and leave you a rebuildable core.

-Kurt

 
Last edited by a moderator:
Wow, Marc! Is that the core I delivered? If there is that much rust, i would worry about the bearings and seals, as well. Rebuilding the diff isn't all that difficult, just tedious and heavy. I've done the 8.8 for my F150, adding an Eaton Posi. The biggest thing is having a shop press. If you do find that you have to rebuild it, and you want to make a run to Memphis one weekend, swing by and we can knock it out.

 
Core in need of a complete rebuild I'm afraid. Everything needs to be disassembled, cleaned, and evaluted for damage.Then buy the complete differential rebuild kit.

 
That looks to have swarf and a broken spider gear ,thats why its frozen rust didn't do that. Not much point hot tanking it cheaper to buy a used 3rd member or buy a new replacement.

 
Wow, Marc! Is that the core I delivered? If there is that much rust, i would worry about the bearings and seals, as well. Rebuilding the diff isn't all that difficult, just tedious and heavy. I've done the 8.8 for my F150, adding an Eaton Posi. The biggest thing is having a shop press. If you do find that you have to rebuild it, and you want to make a run to Memphis one weekend, swing by and we can knock it out.
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I had no idea it was in bad shape. I assumed it was fine, didn't inspect it, but just put it in the back of Ron's truck. Don't waste your effort on it. I'll get another one to you. A 2.75 chunk should be easy. I think my parts car has one in it. I will check now that I'm back home.

 
He's coming over to my place Saturday and we're going to tear down a rear axle assembly I have laying around. If it is any good I'll have him fixed up, if one needs rebuilding-well I have a guy that can help with the set up.
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Cool, Jeff. And you, more than anyone, know why I don't need that 2.75 any more ;) .

The 3.50 still snaps my neck back when the FMX shifts from 1st to 2nd. Thanks again, my friend!!

 
you should ride with me and see what it feels like to shift from 2nd to third at 65 and break the rear end loose enough to make your butt pucker. I took a buddy for a ride and afterwards he said I didn't need seat belts, just a button in the middle of the seat bottom and that the clench would keep passengers in place

 
you should ride with me and see what it feels like to shift from 2nd to third at 65 and break the rear end loose enough to make your butt pucker. I took a buddy for a ride and afterwards he said I didn't need seat belts, just a button in the middle of the seat bottom and that the clench would keep passengers in place
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::beer::

I'll take you up on that one day, sir!

 

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