Spicer Front and Rear Axle Catalog - Manual (Page 4)

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General Information
How To Identify A Spicer Axle
All Spicer Carrier Type axles are identified with a manufacturing date (1) and Bill of Material number (2)
stamped on the right or left hand tube on driving axles. The Bill of Material number may also be found on the
carrier in some models as shown in illustration (2A). For independent front suspension (IFS) axles, the B/M
number may be located at one of three locations: 1). A vertically positioned tag near the center of the right
hand side support arm, 2) stamped into the left hand side support arm (opposite end of the camber adjuster),
or 3) stamped into the "nose end" of the axle carrier. The location of the information will depend on the manu-
facturing date of the axle.
The axle model number will be cast into one of the webs as shown (3), or it can be on the nose.
Each axle contains a gear ratio tag (4), and if the axle is equipped with a limited slip differential, it will have a
tag specifying the type of limited slip lubricant to be used (5).
Refer to the appropriate model number section for parts identification and a breakdown of the Bill of Material.
How To Change Gear Ratios
To increase or decrease a gear ratio, there are certain steps that must be taken. The differential case depends upon the ratio
desired. For each axle model, there is a high-ratio and a low-ratio case as illustrated below:
Axle Model Low Ratio Case High Ratio Case Axle Model Low Ratio Case High Ratio Case
Model 27 3.73 and Down 3.92 and Up Model 50 4.10 and Down —
Model 28 3.45 and Down 3.73 and Up Model 60 4.10 and Down 4.56 and Up
Model 28 IFS Aerostar 2.27, 3.73 — Model 61
Model 30 3.55 and Down 3.73 and Up Semi Float 3.00 and 3.07 only
Model 35 2.35 only — Model 61
Model 35 2.73 - 3.31 3.54 and Up Full Float 3.31 and Down 3.54 and Up
Model 36 ICA 2.73 and Down 3.07 and Up Model 70 4.10 and Down 4.56 and Up
Model 44 3.73 and Down 3.92 and Up Model 70-3HD 3.42 and Down 3.73 and Up
Model 44 ICA Model 70-2UA 3.07 only —
1984 & earlier 3.73 and Down 3.92 and Up Model 80 3.73 and Down 4.10 and Up
Model 44 ICA
1985 & later
2.87 and Down 3.07 and Up
Example - If you have a model 44 Rear Axle with a 3.54 ratio and wish to change to a 3.73 ratio, you change only the ring gear
and pinion assembly. If you change the ratio to a 4.09, you must change to a high-ratio case in addition to changing the ring
gear and pinion. The application section will show you what case to use. When the vehicle is equipped with both front and rear
driving axles, the gear ratios must be the same in both axles. The drive gear screws are self-locking and must be replaced with
new screws each time that they are removed.