Freightliner — FASII

Description

The FAS II is very popular in over-the-road applications with few parts to maintain. It is designed to cushion load and reduce sway in turns. It features an underslung parabolic leaf spring trailing arm.

Freightliner FAS II

Fast Facts

Freightliner — FASII
Type
Features
Problem Areas	OE bonded rubber bushing in the leaf spring trailing arm. The spring eye opens up and results in bushing walk-out.
ATRO Solutions

Tech Tips and Additional Resources

ATRO Spring Pin Solution (PB46-26268 and UB20500-OS):

Rotating pin design with flanged outer sleeve limits travel
The revolving inner pin eliminates bushing wind-up and prevents entire bushing spinning
UB20500-OS, an over-sized version (+.060"), is available if the rubber bushing has opened up the spring eye slightly. The spring must still meet specifications. If not, the spring must be replaced, not rebushed

ATRO Torque Rods

ATRO offers complete replacement rods for the three different length options.

Part Number	Length
TR46-41716	23 15/16"
TR46-41316	22 7/8"
TR46-41002	24 5/16"

The bushing in all three ATRO rods is TS00-22500 – it has a 2" O.D. and will not fit OEM or other aftermarket rods. ATRO added an outer sleeve to extend bushing life also allowing for pin rotation that results in easier bolt hole alignment

To rebush an OE rod or other aftermarket rod for this application, use ATRO’s non-rotating TS50-22691 (retaining rims) or PL1146 (no retaining rims, easy installation), which have no outer sleeve and the standard 1 7/8" outer diameter

Wear Items

The biggest concern is the OE bonded rubber bushing in the leaf spring trailing arm. The spring eye opens up and results in bushing walk-out:

The bonded OE-style rubber bushing does not allow the pin to rotate. Thus, the ENTIRE bushing can be forced to spin, wallowing out the spring eye. (The OE has used multiple designs to solve this including the standard design, high-confinement design and the current anti-walk version.)