Some 2003-09 Honda Pilot SUVs and 2006-09 Ridgeline pickup trucks may produce a groaning noise and/or vibration from the rear while turning. One likely cause, Honda said, is the rear differential clutches grabbing and releasing excessively. Contaminated fluid is the likely cause.
To make the diagnosis, bring the truck to a parking lot and make a few figure-8 turns with the steering wheel positioned at full lock. Make sure you accelerate at the start of each turn to allow the differential clutches to grab and release. If you don't hear the groaning noise and/or feel the vibration, this information doesn't apply.
If you hear the noise and/or feel a vibration, bring the vehicle back to the shop and position it on a lift.
Now, remove the fill and drain plugs from the rear differential and drain the fluid completely. Examine the fluid carefully. It should be bright red. If it's pink, it's contaminated from water getting into the differential through the vent tube.
Continue the fix by installing the drain plug and the old sealing washer. Now, fill the differential with 5-1/2 quarts of VTM-4 differential fluid, part No. 082200-9003, H/C 6512651. Top off the fluid until it's at the bottom of the fill hole, then reinstall the sealing washer and fill plug.
Now, go back to the parking lot and make at least ten figure-8s, again with the steering wheel at full lock to allow the new diff fluid to penetrate the clutch material.
Once back to the shop, put the truck on a lift again. Drain the fluid once more and install the drain plug, this time using a new sealing washer. Now, fill the differential with the VTM-4 fluid to the bottom of the fill hole, and reinstall the fill plug, again using a new sealing washer. Go back to the parking lot one last time and perform another series of figure-8 turns. If the groaning noise and/or vibration is gone, you're done with the fix.
If not, the rear differential will require rebuilding.
"Factory Fixes" is written by Jim DePalma, a 30-year veteran of the auto repair business who has served stints as a service manager, parts manager and ASE-certified technician. His column provides vehicle manufacturers' authentic factory technical service bulletins (TSBs) that have been condensed for easier reading. Mr. DePalma advises that techs always check with a dealer or repair information system for the latest revisions before starting to work on a vehicle. He can be reached via email at [email protected].