Submitted by: StealthV

Items Required:
  • -- Two quarts of GM Synthetic Axle Lubricant SAE 75W-90 GM #12378261 (~$27/quart)
  • -- One 4 oz. bottle of Limited Slip Axle Lubricant Additive GM #1052358
  • -- One 10-mm hex allen wrench
  • -- Suction gun
  • -- Oil drain pan
  • -- Set of ramps or jack stands and a hydraulic jack

The engine, transmission, differential and exhaust will be extremely hot. Be careful, safety first!

2. Before the oil change, drive at least 10-15 miles at 55 mph to so the differential and be sure the fluid is warm and well mixed so any particles are suspended in the oil.

3. With the rear of the Cadillac CTS safely supported, remove the fill plug first. The fill plug is located on the driver's side of the differential, half-way up the side of the differential housing and is a bit tricky to get at with the exhaust pipe in the way. Use both ends of the 10-mm allen wrench to loosen the fill plug.

4. Position the oil drain pan under the differential and remove the drain plug with the 10-mm allen wrench.
Caution! Hot lubricant will come out quickly!

5. While the differential housing is draining, clean up the drain plug. Here's the "before" shot of my plug. The dark glob on the end of the magnetic plug is the metallic paste that has formed from normal bevel pinion gear break-in. This is important as there are metal particles collected on this plug, which is normal.

6. After the lube is done draining, install the clean magnetic drain plug and tighten snugly with the 10-mm allen wrench.

7. Remove the top of the suction gun and fill it half full with the new GM diff lube. Pour in the bottle of limited slip additive and then continue to fill the suction gun body with diff lube until near the top of the gun. Place the top of the suction gun back on, go under the V, place the hose in the fill hole and press in the handle on the suction gun to push the fluid into the diff housing.

8. Once the suction gun is empty, refill with diff lube and continue to fill the differential housing until lubricant begins to spill out of the hole.

9. Reinstall the fill plug on your Cadillac CTS and tighten until snug.

10. Clean up your mess, safely lower the cadillac cts and take it for a spin and enjoy the knowledge that for not much money, you've done your differential a favor.