ALLISON-OM1334EN

fluid in the subject transmission should be sampled again immediately to verify the

exceeded limit. If verified, the fluid should be changed regardless of time or mileage.

AUXILIARY FILTER

If a condition occurs that introduces debris into the transmission hydraulic system, a

complete cleanup of the cooler and lines is recommended.

Repeated cleaning and flushing may not remove all debris. For models with a retarder,

replace the main cooler. For models without a retarder, install an auxiliary filter in the

cooler-out line (between the cooler and transmission) if such a filter does not already

exist. This filter has already been included in many recently built vehicles. This

recommendation applies whether the transmission is overhauled or replaced by a new

or rebuilt unit.

If any doubt exists about the cleanup of the cooler, replace the cooler.

Consult your nearest Allison Transmission dealer/distributor or the chassis OEM for

detailed filter information and availability.

Table 4. Fluid Oxidation Measurement Limits

Condition

Limit

Viscosity

± 25% Change From New Fluid

Carbonyl Absorbance

Total Acid Number (TAN)

Solids

+ 30* Change From New Fluid

+ 3.0** Change From New Fluid

2% By Volume Maximum

Carbonyl absorbance units/cm

mg of KOH required to neutralize a g of fluid

CAUTION:

DO NOT install an auxiliary filter in the AT 500R or

MT 643R primary cooler circuit. This reduces retarder effective-

ness. An auxiliary filter in the secondary cooler circuit is sufficient.

ALLISON-OM1334EN - Page 40 of 48