I recently changed tires on our hundy from Toyo ATIIs to Michelin LTX MS2 to quieten the ride down a bit for some long trips we have coming up, and have discovered that we have a pronounced droning noise at 2500 rpm - which is unfortunately right at our cruising speed of ~ 70 mph. Drone starts around 2400 rpm and then clears up after 2800 rpm.
01 LX 470, 285/75R16, 132k miles
Diagnosis:
- happens in all gears (except maybe reverse? ) and all speeds
- must be under load/in-drive. I don't notice it in P/N, or standing in front of an open hood
- A/C on/off doesn't make a difference
- if engine is turning at 2500 rpm and in 4th (its an 01), and I turn off OD, it shifts down to third, engine goes up to 3300 rpm and sounds and feels quieter. Speed hasn't changed and drive train is still doing the same work - at least down stream of the AT.
Things I've tried:
- re-installed the flux-capacitor ("what is this") with no change.
- cleaned throttle plate, MAF, checked over the intake assembly and we have a new air filter - no change.
Other ideas:
- exhaust? Muffler has some (small) dents from rocks etc in it which have been there a while, but otherwise exhaust system seems good.
- pulleys and idlers on the accessory belt? I think if there was an issue here, it wouldn't need to be in gear and under load?
- wheels are heavy. 285/75R16 are 10 ply and heavy tires. Is the AT complaining about the extra work? I've tried to deflate them a bunch to get the wheel diameter to ground closer to OEM - no difference. Vehicle is heavy; front & rear bumpers, sliders, winch and 16 gal aux tank.
- transmission - is 2500 rpm around a shift point? ATF is good. Level looks good as near as I can tell - though I have hard time with that dipstick. Its either dry (when off) or thoroughly covered once one and I've shifted through all the gears.
- spark plugs and coil packs. 132k miles is about when we are supposed to replace plugs. No error codes. Idle speed in Neutral with AC off is perfect, but in park its low (600 rpm sometimes - AC on).
Other ideas? Best guess is the muffler right now, but that's some work for just trial and error. Turn up stereo and carry-on?
Will appreciate the MUD collective wisdom.
01 LX 470, 285/75R16, 132k miles
Diagnosis:
- happens in all gears (except maybe reverse? ) and all speeds
- must be under load/in-drive. I don't notice it in P/N, or standing in front of an open hood
- A/C on/off doesn't make a difference
- if engine is turning at 2500 rpm and in 4th (its an 01), and I turn off OD, it shifts down to third, engine goes up to 3300 rpm and sounds and feels quieter. Speed hasn't changed and drive train is still doing the same work - at least down stream of the AT.
Things I've tried:
- re-installed the flux-capacitor ("what is this") with no change.
- cleaned throttle plate, MAF, checked over the intake assembly and we have a new air filter - no change.
Other ideas:
- exhaust? Muffler has some (small) dents from rocks etc in it which have been there a while, but otherwise exhaust system seems good.
- pulleys and idlers on the accessory belt? I think if there was an issue here, it wouldn't need to be in gear and under load?
- wheels are heavy. 285/75R16 are 10 ply and heavy tires. Is the AT complaining about the extra work? I've tried to deflate them a bunch to get the wheel diameter to ground closer to OEM - no difference. Vehicle is heavy; front & rear bumpers, sliders, winch and 16 gal aux tank.
- transmission - is 2500 rpm around a shift point? ATF is good. Level looks good as near as I can tell - though I have hard time with that dipstick. Its either dry (when off) or thoroughly covered once one and I've shifted through all the gears.
- spark plugs and coil packs. 132k miles is about when we are supposed to replace plugs. No error codes. Idle speed in Neutral with AC off is perfect, but in park its low (600 rpm sometimes - AC on).
Other ideas? Best guess is the muffler right now, but that's some work for just trial and error. Turn up stereo and carry-on?
Will appreciate the MUD collective wisdom.