Axles, Consumables, differential, Lubricants

Oil Levels in Drive Axles

oil levels in drive axles

It seems obvious, but keeping an eye on oil levels in drive axles is a vital part of any maintenance regime.

Checking oil levels in Meritor drive axles is a relatively simple procedure however, there are certain factors that require attention.

Make sure the vehicle is parked on a level surface. The vehicle must be in the horizontal position. When the angle of the drive pinion changes, the lubricant capacity of the axle will change.

It’s important to note the correct oil level plug for a Meritor drive axle as the position for the correct oil level plug may differ between axle models and could also be influenced by drive axle installation angles within the vehicle chassis.

Fill Plug Locations

If the only fill plug found on your drive axle is in the axle housing bowl, use that fill plug. Do not use the temperature sending unit hole

Some axles do not have temperature sender units for axle temperature gauges in the vehicle, so a plug is fitted to blank off the hole. Do not mistake this temperature sending unit hole as a fill plug as this will result in an under capacity filled axle and damage to axle components may occur. If a temperature sender unit is not fitted, this plug can easily be mistaken for an oil level plug.

Refer to following drawings.

oil levels in drive axles

oil levels in drive axles

In axle models where the drive axle differential carrier has an oil level plug on the side of the carrier and the pinion angle is seven degrees or less, use the fill plug in the differential carrier.

If the drive pinion angle is more than seven degrees, use the fill plug in the axle housing bowl.

Refer to following drawings

oil levels in drive axles

oil levels in drive axles


Older model axles may have a separate fill plug for the inter-axle differential (power divider) unit but the overall axle oil level plug will be on the carrier or the axle housing.

On axles with an inter-axle differential fill plug (as per below), remove the plug on the top of the axle housing. Place 0.946 litres of the specified lubricant via this plug and then continue to fill the assembly via the correct fill plug in the differential carrier or the axle housing.

Refer to following drawings.

oil levels in drive axles

oil levels in drive axles

Below is the fill/level plug position for the front drive axle carriers in axle models:

  • RT and RP 180 Series
  • RT and RP 380 Series
  • SR 170
  • ST 170
  • SPRC 1927

The rear rear drive axle carrier in these models will have a fill / level plug on the left side of the carrier.

oil levels in drive axles

Checking the Oil Level

Check the oil level when the axle is at room temperature. When hot, the oil temperature may be 80°C or more and can cause burns. A correct level is not obtained when the axle is hot. Serious personal injury and damage to components can result.


1. Park the vehicle on a level surface. Place blocks under the front wheels to prevent the vehicle from moving. The axle must be cold or near room temperature.

2. Clean the area around the fill plug. Remove the fill plug from the differential carrier or the axle housing bowl, depending on the axle. Do not remove the temperature indicator plug.

3. Check the oil level. The level must be even with the bottom of the fill plug hole.

4. Install the fill plug. Tighten the plug to 35-50 lb-ft (48-67 Nm).

For further information, refer to the Meritor Preventive Maintenance and Lubrication, Maintenance Manual 1

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