The oil level is low.

Add oil in order to attain the proper fluid level. Refer to Transmission Fluid Check .

The clutch pressure is low.

Test the pressure.

The forward clutch slips.

Repair the forward clutch.

Refer to applicable Allison Transmission Service Manual.

The first clutch slips.

Repair the first clutch.

Refer to applicable Allison Transmission Service Manual.

The fourth clutch (reverse) is slipping.

Repair the fourth clutch.

Refer to applicable Allison Transmission Service Manual.