wish someone had a decoder for it
I agree. I've written and talked w/Ford Customer Service a few times asking for a Decoder/Legend, but got no info and with letters/e mails, no response.
Some itmes can be looked-up such as your H5 rear Axle Code;
Bronco, Rear from 85 & 90 Owner's Manuals; Note, I'll add that the axle code for some years (Maybe all ) adds a 2 after the limited slip code if the front is also limited slip. So the code "H9" is a 3.55:1 limited slip rear axle only. "H92" would be a 3.55:1 limited slip on both axles. by ElKabong (Ken, El Kabong)
Source: by Ford & Helm via Keith L (TTB Blows, Bling-Bling) at homestead.com via web.archive.org
Now go get your owner's manual, it usually comes w/the truck and says "Owner's Manual" or similar in english on the cover. Damnit, I already hear your whining, "I lost my owner's manual. . . " Stop. Helm Publishing will be happy to sell you a new one, and even if you're an experienced gearhead the owner's manual makes good bedtime reading. It'll tell you stuff like fluid capacities, towing capacities (ever wonder exactly how much tongue weight that stock step bumper is rated at??), and all sorts of other cool stuff. So stop the whining and click
Now, here's the combined codes from '85 and '90 Bronco owner's manuals; this should cover most if not all codes out there:
REGULAR: (Regular means "open" diff in this context)
If you have 3 digits on your axle code the first two digits are the rear axle code. Thus, looking at my pics above and cross-referencing the chart above my '90 came from the factory w/3.55's and Ford's sorry excuse for a limited slip differential, the Crap-Lok, er I mean Trak-Lok.
Now, to know if the front diff is open or limited slip I'm ass-uming you have to look for a tag on the diff, as there is no "front axle code" on the door jamb sticker.
"...Ford typically builds 4WD trucks with a slightly faster/numerically lower front gear ratio than the rear so that off-road steering is enhanced. So a truck built with 3.55 rear gears will have 3.54 front; 3.08 rear - 3.07 front; 4.11 rear - 4.10 front, etc..." Following was in my MS WORD Notes and the source, Randy's Ring & Pinion has removed it from their current web site; The gear ratio in the front of a four wheel drive has to be different from the front so the front wheels will pull more. There have been many different ratio combinations used in four-wheel drive vehicles, but not so that the front will pull more. Gear manufactures use different ratios for many different reasons. Some of those reasons are: strength, gear life, noise (or lack of it), geometric constraints, or simply because of the tooling they have available. I have seen Ford use a 3.50 ratio in the rear with a 3.54 in the front, or a 4.11 in the rear with a 4.09 in the front. As long as the front and rear ratios are within 1%, the vehicle works just fine on the road, and can even be as different as 2% for off-road use with no side effects. point difference in ratio is equal to 1%. To find the percentage difference in ratios it is necessary to divide, not subtract. In order to find the difference, divide one ratio by the other and look at the numbers to the right of the decimal point to see how far they vary from 1.00. For example: 3.54 ÷ 3.50 = 1.01, or 1%, not 4% different. And likewise 4.11 ÷ 4.09 = 1.005, or only a 1/2% difference. These differences are about the same as a 1/3" variation in front to rear tire height, which probably happens more often than we realize. A difference in the ratio will damage the transfer case. Any extreme difference in front and rear ratios or front and rear tire height will put undue force on the drive train. However, any difference will put strain on all parts of the drivetrain. The forces generated from the difference have to travel through the axle assemblies and the driveshafts to get to the transfer case. These excessive forces can just as easily break a front u-joint or rear spider gear as well as parts in the transfer case.
Source: by miesk5 at Ford Bronco Zone Forums