Hi all,
Read through what posts I could find on this (plus a million YouTube vids) and looking for some help! I have an odd, low humming noise I can hear when driving the 80. It’s harder to hear at lower speeds, say under 35-40 or so, though if I listen and make sure the climate control is off and there’s no music, and on a relatively smooth patch of road, I can make it out.
It sounds like a steady, constant background hum, that gets much more audible above 45 or so, and seems to peak at around 2100 RPM (with overdrive on or off). By then, it’s clearly audible. It doesn’t vary in tone or sound. It’s a constant low hum. No grinding or odd vibrations. When I let my foot off the accelerator, especially at around 2000 RPM, I can hear this “winding down” noise. Imagine a turbine winding down, like that; the humming “winds down.” If I put pressure on the accelerator again, the winding down noise goes away and the hum returns.
I do not hear it if I go at higher speeds but with no load on the engine. Like say if I go downhill and just let the car reach 40-45 on its own, no acceleration, then I don’t hear anything. I had a wheel bearing noise before. I rebuilt the front axle and that solved it. This is a bit of a different sound, less grind more hum, and doesn’t happen without load on the powertrain.
I also replaced the driveshafts with new OEMs, both front and rear. The front driveshaft’s differential-side u-joint had given up the ghost. The rear seemed okay. Regardless, both are brand new now and properly greased, with no overgreasing of the slip yoke (made sure of that). They are properly phased (one in phase, one out of phase). I used to have the classic clunk when shifting into/out of D and R but that’s now mostly gone. It’s a stock height vehicle, pretty sure it’s the same old OEM springs it came with. No water crossings or contact with high water of any kind.
When I was replacing driveshafts, I did test drives with the center diff locked, once with the rear shaft out and once with the front shaft out. The noise remained essentially the same, regardless.
One last, seemingly important, thing that used to not happen but now does: I have essentially little to no slip when driving on 4 high, with or without the center diff locked, but when I go into 4 low, the car slips. I can rev with essentially no increase at all in speed. RPMs go up and up, speed doesn’t change at all. That to me suggests torque converter slip, but seemingly only on 4 low. So could that then be the transfer case? I don’t recall it previously doing this. Of course, 4 low was slower but it didn’t just result in rev-ing with no change at all in speed, only to sometimes catch and move slightly faster.
Any insight is appreciated! The gear oil in the diffs and transfer case has been changed recently. The transmission fluid was changed (not flushed) about 2-ish years ago (about 18,000 miles ago or so), just after I got the car. The level seems fine on the dipstick, no burning smells. Gear shifting is fine, seems normal. Planning on doing another transmission fluid change sometime soon. Would all of this point to something in the torque converter, transmission, or transfer case?
Read through what posts I could find on this (plus a million YouTube vids) and looking for some help! I have an odd, low humming noise I can hear when driving the 80. It’s harder to hear at lower speeds, say under 35-40 or so, though if I listen and make sure the climate control is off and there’s no music, and on a relatively smooth patch of road, I can make it out.
It sounds like a steady, constant background hum, that gets much more audible above 45 or so, and seems to peak at around 2100 RPM (with overdrive on or off). By then, it’s clearly audible. It doesn’t vary in tone or sound. It’s a constant low hum. No grinding or odd vibrations. When I let my foot off the accelerator, especially at around 2000 RPM, I can hear this “winding down” noise. Imagine a turbine winding down, like that; the humming “winds down.” If I put pressure on the accelerator again, the winding down noise goes away and the hum returns.
I do not hear it if I go at higher speeds but with no load on the engine. Like say if I go downhill and just let the car reach 40-45 on its own, no acceleration, then I don’t hear anything. I had a wheel bearing noise before. I rebuilt the front axle and that solved it. This is a bit of a different sound, less grind more hum, and doesn’t happen without load on the powertrain.
I also replaced the driveshafts with new OEMs, both front and rear. The front driveshaft’s differential-side u-joint had given up the ghost. The rear seemed okay. Regardless, both are brand new now and properly greased, with no overgreasing of the slip yoke (made sure of that). They are properly phased (one in phase, one out of phase). I used to have the classic clunk when shifting into/out of D and R but that’s now mostly gone. It’s a stock height vehicle, pretty sure it’s the same old OEM springs it came with. No water crossings or contact with high water of any kind.
When I was replacing driveshafts, I did test drives with the center diff locked, once with the rear shaft out and once with the front shaft out. The noise remained essentially the same, regardless.
One last, seemingly important, thing that used to not happen but now does: I have essentially little to no slip when driving on 4 high, with or without the center diff locked, but when I go into 4 low, the car slips. I can rev with essentially no increase at all in speed. RPMs go up and up, speed doesn’t change at all. That to me suggests torque converter slip, but seemingly only on 4 low. So could that then be the transfer case? I don’t recall it previously doing this. Of course, 4 low was slower but it didn’t just result in rev-ing with no change at all in speed, only to sometimes catch and move slightly faster.
Any insight is appreciated! The gear oil in the diffs and transfer case has been changed recently. The transmission fluid was changed (not flushed) about 2-ish years ago (about 18,000 miles ago or so), just after I got the car. The level seems fine on the dipstick, no burning smells. Gear shifting is fine, seems normal. Planning on doing another transmission fluid change sometime soon. Would all of this point to something in the torque converter, transmission, or transfer case?
