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From the rear of the car in a very narrow window between engine breaking and being on power (think feathering the throttle behind a slower car waiting to pass) there's a low rumble. Almost like a bad subwoofer.
Raised the car and checked diff fluid. Have plenty (factory fill with just under 8K on it). Wiggled everything back there and it's all tight. Tried to move the driveshaft up and down perpendicular to the pinion shaft in case it might be pinion bearings but can't really get enough grip to do that with the heat shield in the way. Doesn't seem to be any excessive backlash in the diff.
10 + year old diff oil ? Start there and see if it changes anything. Dont forget a little LSD additive. The coast point between acceleration and deceleration loads often creates a whine, not a rumble, and you dont have enough miles for teeth mesh issues unless Pinion and Ring gear were not correctly set up in the first place. Rumbles are usually bearing related IMO. Could be one of the diff bearings or one of the wheel bearings, but if ones bad, it should be apparent much more often than your coast window. Id start with the oil change and go from there.
Pay close attention to the oil as it comes out and hope its just old and dirty.
Brand new Pilot Sport AS3+ installed last month. I'll start with the diff fluid change. I'd planned to do it with the next engine oil change at 10k. Won't hurt to be a little early.
Originally Posted by CaymanRotary
How are your tires? Maybe something out of balance.
Brand new Pilot Sport AS3+ installed last month. I'll start with the diff fluid change. I'd planned to do it with the next engine oil change at 10k. Won't hurt to be a little early.
Just make sure the additive for limited slip diff is added to the new fluid. Always good to be on top of fluid changes.
I'm less concerned after paying more attention while out driving around this evening. I'm thinking I'm just hearing some sort of resonance out of the trunk. I noticed I heard noises of a similar frequency as the rear tires were going over broken pavement. Also wound up in some stop & go traffic crawling along in 2nd and if we came to a quick halt I'd hear the same frequency diminishing with engine revs when I'd hop on the clutch rather than being related to wheel speed.
Lastly we were in a drive thru later on and INXS "What You Need" (80s on 8 FTW!) came on and bass hits would make the exact same sound frequency.
I'm going to change the diff fluid anyway since I now have it on hand but I'm thinking the sound I'm hearing is just the body resonating to natural vibrations.
Did both diff and transmission fluid today. Transmission was still mostly translucent like new oil is but differential was fully opaque so despite only 7,800 miles 11 years was just as bad as high mileage.
Did both diff and transmission fluid today. Transmission was still mostly translucent like new oil is but differential was fully opaque so despite only 7,800 miles 11 years was just as bad as high mileage.
Oil breaks down over time. Even if it isn't being used. Definitely was a good idea to replace with fresh fluids. May want to do new brake fluid as well.
09-29-2020, 08:09 PM
