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new gears on back differential?

 
Old 11-16-2018, 02:05 PM
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Hi all

I have a '78 f150 4x4 and the back diff (or the half shafts.. don't know yet til I open it) has died on me... basically the propshaft just spins in drive. anyway, when I go for a rebuild if it is in fact the diff, can gear ratios just be swapped or does anything else need done? is it a case of throwing in a new ring and pinion? from what I can tell, it's a ford 9" differential, and I'm looking at 4.11 or 4.56. thanks in advance
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Old 11-16-2018, 02:15 PM
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if you regear the rear you have to do the front, and on a 9'' you can just swap the whole center section, you can buy them pre built
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Old 11-16-2018, 02:37 PM
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Brilliant, thanks for getting back to me. I'm in Scotland so spares are not too easy to come by so I'll just have to toss up between what will work out better, both money, time and postage costs. I have difflocks as well (not sure if that's standard - a lot of 4x4 sales offer them as extras here)... are the pre built units compatible with them? I've only ever swapped out like-for-like components on axles so re-gearing is a new one to me.
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just added the pic to confirm it is the ford 9"
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Old 11-16-2018, 02:40 PM
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those trucks did not come factory with lockers(i think anyway) limited slips yes those were an option but full on lockers no

I'd be very suprised to see if anything broke in the rear, those axles are damn near bulletproof
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Old 11-16-2018, 03:02 PM
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my 4x4 selector stick has 4L lock, 4L, N, 4H, and 4H lock so I assumed it was factory. my rear prop spins but gives no drive so either the diff is humped, or one of the shafts has sheared. will probably open it over the weekend to see what's happened
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Old 11-16-2018, 03:05 PM
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Originally Posted by TheBigMac View Post
my 4x4 selector stick has 4L lock, 4L, N, 4H, and 4H lock so I assumed it was factory. my rear prop spins but gives no drive so either the diff is humped, or one of the shafts has sheared. will probably open it over the weekend to see what's happened
are you sure its factory 4wd and not converted?
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Old 11-16-2018, 03:11 PM
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in all honesty, I do not know. it all *looks* factory but being in Scotland, there are none others of these around to compare it to. it's the long wheelbase supercab if that's any use. was a camper as well but I didn't want the camper shell.
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Old 11-16-2018, 03:13 PM
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