26–01 Manual Transmission
Fluid Level Checking
1. Park the vehicle on a level surface. Apply the
parking brakes and chock the rear tires.
2. With the transmission at operating temperature
(Eaton Fuller transmissions) or at room tempera-
ture (Meritor transmissions), check the oil level in
the transmission.
2.1 Clean the area around the fill plug, then
remove the plug from the side of the
case.
2.2 Using your finger or a bent pipe cleaner,
see if the oil is level with the lower edge
of the fill opening. See Fig. 1.
3. If needed, fill the transmission with oil until level
with the lower edge of the fill opening.
See Table 1 for approved lubricants.
CAUTION
Operating a manual transmission with the oil level
higher or lower than recommended can result in
transmission damage. Do not overfill the transmis-
sion; overfilling will force oil out of the case
through the main shaft openings. Oil overflow
may also drain onto the clutch or clutch brake,
causing additional problems.
IMPORTANT: Do not mix types of oil, because
of possible incompatibility. Do not use oil addi-
tives or friction modifiers. Do not use multi-
viscosity oils or EP (Extreme Pressure) gear
oils. If switching from a petroleum based lubri-
cant to a synthetic, all areas of each affected
component must be thoroughly drained. Switch-
ing to a synthetic lubricant, when a petroleum-
based lubricant has been used for 50,000 miles
(80 000 km) or longer, may affect transmission
performance. Monitor all seal areas for the first
10,000 miles (16 000 km) after changing to a
synthetic from a petroleum-based lubricant.
4. Clean the fill plug, then install it in the gear case.
Tighten the plug as follows:
Approved Manual Transmission Lubricants
Lubricant Type
*
Temperature
in °F (°C)
SAE
Viscosity
Eaton Fuller Transmissions
†
MobilTrans SHC 50 (RN
2952 E-5)
All 50
Synthetic transmission
lubricant approved by Eaton
All 50
Heavy-duty engine oil (API
service classification SF or
CD)
Above 10 (–12) 40 or 50
Below 10 (–12) 30
Meritor Transmissions
Heavy-duty engine oil (API
service classification CD,
CE, SF, or SG)
Above 10 (–12) 40 or 50
Above –15
(–26)
30
Mineral gear oil With rust
and oxidation inhibitor (API
GL–1)
Above 10 (–12) 90
Above –15
(–26)
80
Synthetic transmission
lubricant meeting Meritor
specification 0–81
All 50
Mercedes-Benz Transmissions
MobilTrans SHC 50 (RN
2952 E-2)
All 50
*
Lubricants listed in order of preference. Do not mix types of oil.
†
Call 1-800-826-4357 for a complete list of Eaton approved lubricants.
Table 1, Approved Manual Transmission Lubricants
• 25 to 35 lbf·ft (34 to 48 N·m) for Eaton
Fuller transmissions with 3/4-inch pipe
threads.
• 60 to 75 lbf·ft (81 to 102 N·m) for Eaton
Fuller transmissions with 1-1/4-inch pipe
threads.
• 35 to 50 lbf·ft (48 to 67 N·m) for all Meritor
transmissions.
f260006b
10/05/94
A
B
A. Full B. Low
Fig. 1, Transmission Fluid Level Checking
Transmission 26
Business Class Trucks Maintenance Manual, February 2003 26/1
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