NavigatorPro
Well-known member
- Joined
- Mar 19, 2022
- Messages
- 355
- Reaction score
- 254
- Points
- 63
- My Lincoln
- 2018 and 2021 Lincoln Navigator L
Whats been happening is a humming noise on the drivers side left at around 45 mph upon deceleration. It is not a bearing noise but a gear noise. The sound is oftentimes confused with the hub and bearing. If it were a bearing noise you would hear the sound constantly but upon applying power the hum goes away indicating its a gear noise.
When you hear the noise it indicates the gear inside the front diff has become damaged. Fortunately the front differential is easy to replace. Ford has made a one stop kit part# S-993-K which includes all parts needed for replacement. If you doing this outside of warranty the part costs about $700 when purchased online.
If you have a new 2025+ you should change the fluid to 75w-140 Amsoil Severe Gear and 1 tube of Liqui Moly Mos2 Antifriction for gears. The diff holds 2 quarts. This gear oil is twice as thick and help protect the gear inside...prevent it from happening again.
When changing fluid you need a siphon sold at Harbor Freight. Any good mechanic has their own siphon to drain the fluid out. The drain/fill hole is not hard to access if you crawl underneath. Whatever you do absolutely do not open the differential. You will cause a leak that will need to be sealed with Permatex Optimum Grey. Only use a siphon!
On the 2022+ Ford Expedition/Lincoln Navigator this best describes the situation. The front differential was never designed to be activated all the time but in the 2022+ models its on all the time. The fluid inside is the thinnest available that cant properly protect the gear.
When you hear the noise it indicates the gear inside the front diff has become damaged. Fortunately the front differential is easy to replace. Ford has made a one stop kit part# S-993-K which includes all parts needed for replacement. If you doing this outside of warranty the part costs about $700 when purchased online.
If you have a new 2025+ you should change the fluid to 75w-140 Amsoil Severe Gear and 1 tube of Liqui Moly Mos2 Antifriction for gears. The diff holds 2 quarts. This gear oil is twice as thick and help protect the gear inside...prevent it from happening again.
When changing fluid you need a siphon sold at Harbor Freight. Any good mechanic has their own siphon to drain the fluid out. The drain/fill hole is not hard to access if you crawl underneath. Whatever you do absolutely do not open the differential. You will cause a leak that will need to be sealed with Permatex Optimum Grey. Only use a siphon!
On the 2022+ Ford Expedition/Lincoln Navigator this best describes the situation. The front differential was never designed to be activated all the time but in the 2022+ models its on all the time. The fluid inside is the thinnest available that cant properly protect the gear.
