EDIT: I see that my friend here Seabronc has already answered your Q; I started my reply, but took my 5 min break that turned into ... lol
I made a mistake 15 years ago by telling someone to use the Driver's side door label to ID their Rear Differential (axle, pumpkin type, etc.); turned out that a previous owner had swapped a Dana 60 in place of the stock 8.8
so... a run down; read about the gear ratio here in the Bronco Zone Forums @ http://broncozone.com/topic/20082-help-me-need-to-know-specs-88-bronco-xlt-58l-351w/
The 8.8 is probably in your Bronco;
Information, History, ID, pics, etc.
Source: by Kenneth C at Bad Shoe Productions badshoeproductions.com
Photo 1 - The 9” rear ends have a removable “hog-head” center carrier and is about 10” from the bottom to the top stud. The 9” was introduced in 1957 and ran to mid 80's.
Photo 2 - The 8" rear was use from the 60's to the late 70's, top to bottom stud is about 9".
Photo 3 - 8.8” rear’s have a ten bolt inspection plate on the back that’s about 10” from the center of the top bolt to the bottom bolt center. The 8.8” first saw service in the 79 Crown Vic. and in 1980 for the F100/150.
Photo 4 - The 7.5” rear was first put in the 78 Fairmont. It also has a ten bolt cover but measures about 9” from top to bottom bolt.
Door Jamb Label (Data Plate, also referred to as the Patent Plate & the Warranty Plate) http://www.supermoto...a.php?id=219542
As an example, a pic for a 94
Source: by Adrianspeeder (The OJ Special, The Lariat, The Bronco) at http://www.supermotors.org/vehicles/registry/showmedia.php?id=219542
from this Plate; you could assume you have a rear diff code of 19 installed in his Bronco;
Basing on this;
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. http://classic-web.archive.org/web/20020220012159/http://90bronco.homestead.com/axlecode.html
REGULAR: (Regular means "open" diff in this context)
Source: by Ford & Helm via Keith L (TTB Blows, Bling-Bling) at homestead.com via web.archive.org
CODE 19 = 3.55 ratio
and that would be for a Ford 8.8 diff
"H92" would be a 3.55:1 limited slip on both axles. by ElKabong
Bronco & F Series Differential, Front & Rear Brands in 91-96
Source: by Steve83
A Visual Check
Gear Ratio Determination; "Another way is to remove the differential cover or the 3rd member and count the number of teeth on the gears. Unfortunately, this can get messy. However, it does tell you without a doubt what kind of traction control device you may have...jack up the wheels, disconnect the driveshaft, rotate one wheel, and count how many revolutions the pinion yoke/****** makes..." Read More @ http://www.jedi.com/obiwan/jeep/misc/gearratio.html
Source: by Obi-Wan
Ford built our Broncos & other 4x4 trucks & vans with a numerically lower front gear ratio in the front Dana 44 than the rear so that off-road steering is enhanced. A Bronco built with 3.55 rear ratio would have a 3.54 ration in the front Dana 44; or; 3.08 in the 8.8 & 3.07 in the Dana 44; or 4.11 in the 8.8 & 4.10 in the Dana 44, 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. by Randy's Ring & Pinion
Front; Dana 44
Three types of Dana front-drive axles are available for Ford light truck application. The Dana 44-IFS (Independent Front Suspension) is available on Bronco and F-150 4x4. The Dana 50-IFS (Independent Front Suspension) is available on F-250 4x4. The third type of front drive axle is the Dana Model 60 Monobeam. Refer to Section 05-03B for more information.
The axles are basically alike with some differences between the three. The 44-IFS is on vehicles equipped with front coil springs. The 50-IFS is used on vehicles equipped with front leaf springs.
The 44-IFS and the 50-IFS may be equipped with either automatic hubs or manual locking hubs.
The front axle is of the integral carrier-housing, hypoid gear type, in which the centerline of the drive pinion is mounted above the centerline of the ring gear.
On IFS front driving axles, the cover on the front of the carrier housing is integral with the left axle arm assembly. A mylar tag, with the gear ratio and part number, is attached to the rear face of the right-hand axle support arm.