GMC C-Series 2001 Owner's Manual page 222

Automatic Transmission External Filter
Your automatic transmission spin
periodic replacement. It is mounted just behind the
radiator on the outside of the passenger's side frame rail.
Consult the Allison Automatic Transmission Operator's
Manual that came with the vehicle for proper
change intervals.
Automatic Transmission External Filter
With Service Trans Filter Indicator
Light (Option)
This automatic transmission spin
mounted to the left of the transmission, if your vehicle
has this option. It requires replacement when the
SERVICE TRANS FILTER indicator light on the
instrument panel comes on or every three years,
whichever occurs first.
6-20
-
on type filter requires
-
on type filter is
Manual Transmission Fluid
When to Check
A good time to have it checked is when the engine oil is
checked. See your Maintenance Schedule to find out
when to change your transmission fluid and filters.
How to Check and What to Use
The Eaton Fuller Transmission Operator's Manual that
came with the vehicle shows how to check the manual
transmission fluid and what fluid to use.
NOTICE:
Too much or too little fluid can damage your
transmission. Too much can mean that some of
the fluid could come out and fall on hot engine
parts or exhaust system parts, starting a fire. Be
sure to get an accurate reading if you check your
transmission fluid.