Rear End Identification - Ford Bronco Forum
 
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post #1 of 15 (permalink) Old 01-31-2010, 11:15 PM Thread Starter
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Rear End Identification

Hi-
I have a 1987 Bronco Eddie Bower Edition and my whole rear end is going out. The shop said the gears in the rear differential are bad and are going out. I decided the best way to go is to either get a rebuilt rear axle or get a new rear axle from a junkyard, rather than rebuilding it. How do I figure out what rear axle I have and how do I make sure I get the same thing?
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post #2 of 15 (permalink) Old 02-01-2010, 01:02 AM
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You have an 8.8.You could swap in a ford 9''.Just make sure you get one with the same gear ratio as your old one so it matches the front.The most common ratio was 3.55 for a 8.8 and 3.50 for a 9'' in a Bronco.An axle from a f150 would bolt in as well.

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post #3 of 15 (permalink) Old 02-01-2010, 09:11 AM Thread Starter
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I was also looking, I could buy a Jasper one. But, theyre expensive. If I get one from the junkyard, how do I figure out its gear ratio and what things do I look for to get one in good condition? Maybe I could find a rebuilt one on a Bronco. Whats the difference between a Ford 8.8 and a Ford 9? Is there a better rear end that will work with the stock drive train? What if the gear ratios aren't the same? Jasper asks for a axle ratio, whats that?
Thanks-
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post #4 of 15 (permalink) Old 02-01-2010, 12:55 PM
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In simple terms, your axle ratio refers to how many times the drive shaft turns to make the tire(s) turn one complete circle.
There should be a tag bolted to the inspection cover on your 8.8 Axle. It'll tell you the gear ratio.
There's also an Axle ID number on the door plate.
If you can't find either of those, pull the inspection cover and count the pinion and ring gear teeth, divide the number of pinion teeth into the number of ring gear teeth to get the gear ratio. Unless you bought the truck new, this is the most reliable way to tell the ratio anyway. Ya never know what a previous owner may have done before you ended up with the truck.

Things to note:
Ford's 9" rear is far superior to their 8.8"....and not only because the guts of the thing is bigger overall. Compaired to the 8.8, the 9" is very easy to work on when nessessary, it has a rear support bearing for the pinion and has a better axle bearing/bearing retainer design. Having said that though, it will NOT have the exact ratio as a simular 8.8. What that means is that you will NOT be able to use your 4-wheel drive unless it is on a surface that allows the rear tires to slip a bit. That is because your front axle and rear axle must match as to ratio (as does tire size) or something in the drive train will either slip (or break). As she sits now, your axle ratios are PROBABLY 3.55(R)/3.54(F). You swap in a 9" and they'll PROBABLY be 3.50/3.54.....which is even more of a miss-match than Ford put in to start with.

Do your homework before plunking down your money.

DGW

1989 Bronco 4X4 351W EFI C-6 3.54/3.55 Gears.
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post #5 of 15 (permalink) Old 02-01-2010, 02:08 PM
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I had a 200,000 mile bronco rearend {8.8} go out on me and when I pulled the cover off the gears and bearings were fine but the spider gears and their shafts were shot and loose, Maybe you just need a center carrier thingie with spider gears 'i forget the name of this stuff' If a shop doesnt need to reset the pinion you will save the cost of the ring and pinion gears and the labor.
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post #6 of 15 (permalink) Old 02-01-2010, 08:12 PM Thread Starter
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Nah, the pinion gear is bad too. Shop said everything is bad. I did buy the truck new. so, is that slight mismatch on the gear ratios the reason you shouldn't drive with 4WD any long distance on pavement? If a axle ratio, is how many times the drive shaft spins versus how many times the wheels turn, then what is the gear ratio?
Thanks-
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post #7 of 15 (permalink) Old 02-01-2010, 10:02 PM
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Originally Posted by asdaven View Post
Nah, the pinion gear is bad too. Shop said everything is bad. I did buy the truck new. so, is that slight mismatch on the gear ratios the reason you shouldn't drive with 4WD any long distance on pavement? If a axle ratio, is how many times the drive shaft spins versus how many times the wheels turn, then what is the gear ratio?
Thanks-
Axle ratio and gear ratio are one in the same. If you bought the truck new than just tell us what the door code says under axle.

Did the shop show you the worn out parts or did the rearend grenade or something?

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post #8 of 15 (permalink) Old 02-01-2010, 11:06 PM Thread Starter
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They said everything was worn out and it could last anywhere from 6 months to 10 years. Its slowly been going out in the last 10 years, so I have a good amount of time to shop around. Its been making like a humming noise when I step on the gas. Then, theres a "clunk" when i step on the accelerator at speed, which they said is a combination of worn rear end components and a stretched transfer case chain.
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post #9 of 15 (permalink) Old 02-07-2010, 08:10 AM Thread Starter
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Did any later model broncos come with rear ends with disc brakes?
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post #10 of 15 (permalink) Old 02-07-2010, 08:53 AM
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8.8 was used up to 96 with the 5x5.5 lug pattern. Also look at F150's that are 4x4 because the are the same rear end.
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post #11 of 15 (permalink) Old 02-07-2010, 11:03 AM
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Did any later model broncos come with rear ends with disc brakes?
No, did you figure out what axle/gear ratio you have yet?

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post #12 of 15 (permalink) Old 03-16-2010, 09:00 PM Thread Starter
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I ve been looking more at junkyards for a new rear-end. My buddy says I should get a limited-slip rear end. What does that mean and how do I find out if I have a limited-slip one now? If it is standard, would it change anything if I throw in a limited-slip?
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post #13 of 15 (permalink) Old 03-17-2010, 08:29 AM Thread Starter
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bump
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post #14 of 15 (permalink) Old 03-17-2010, 11:00 AM
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the stock limited slips are junk, I'd avoid them.

They're basically little clutch packs on the diff that reduce the amount of differentiation that occurs (they make the axle shafts spin closer to the same speed).

Limited slips and open diffs are completely interchangable.

Your axle code will be H9 if you have 3.55s and a limited slip. It'll be 19 with an open diff/3.55s.

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post #15 of 15 (permalink) Old 03-17-2010, 05:49 PM Thread Starter
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So, what should I do about finding a axle from the junkyard? Can I find a Ford 9 that is 3.55? What about the Rear ABS? Could I just disconnect that if I find a axle without ABS? How does that interchange? Plus would I need new brake lines?
Thanks-
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