rear end hum?

[johnnyw]

I just picked up an 03 explorer, the rear end makes a humming almost grinding noise. Was told it's no big deal but I still want it gone! Would the crush sleave be the problem?

 

[imp]

I just picked up an 03 explorer, the rear end makes a humming almost grinding noise. Was told it's no big deal but I still want it gone! Would the crush sleave be the problem?

How many miles on the vehicle? How loud is noise, bearable, or scary? There at all speeds? Worse or less at cruise when you accelerate? What yer told may be right. It could be bearing noise, or gear noise. The crush sleeve likely has nothing to do with the noise, assuming the pinion assembly has not been f$%ked with recently.

Check lubricant level, look for evidence of leakage indicating it could be low. This one's not rocket science. Can't tell you more without more info. imp

 

[TechGuru]

Differential needs rebuild just like mine. There is even a TSB on this issue: http://files.mediahost.cf/DIFFERENTIAL_NOISE_TSB.pdf

I've put about 8000 miles on like that, drown it out with big stereo, lol.

Here is the kit I plan to get for my 3.73, if yours is a different ratio they should have that at the same price.

http://www.ebay.com/itm/171179716852

Here is a good 2+ hours worth of video on how to do the rebuild, the main difference is a IRS does not have c-clips:

 

[shadowless127]

if it's a hum, it's typical of these 3rd gens. Had it on my Silver 03 when I purchased it at 60K miles, never had an issue. My mom has had it in her Aviator since 65K miles, and she's at almost 130K.

Now, if it's GRINDING, then it needs to be rebuilt.

 

[rocco123]

My last rear end hum on my 02 was the right rear bearing. I pressed in a new one and hum is gone. Looked at the old bearing and found the inner race was beginning to rust.

 

[Hugh Janus]

If it hums during a load, quiet during coast, then most likely the carrier bearing are worn.

 

[plasticseng]

If it hums during a load, quiet during coast, then most likely the carrier bearing are worn.

Mine has been doing that for 100,000 miles. I changed the fluid out for the synthetic that the TSB prescribed, and it helped a little. It doesn't seem to be getting any worse, so I'm driving it.

 

[Hugh Janus]

Mine has been doing that for 100,000 miles. I changed the fluid out for the synthetic that the TSB prescribed, and it helped a little. It doesn't seem to be getting any worse, so I'm driving it.

The ring-pinion backlash gets large, which is usually the source of the sound.

 

[TechGuru]

The ring-pinion backlash gets large, which is usually the source of the sound.

Can one get away with just re-shimming the carrier to bring the backlash into spec or is a rebuild a must?

 

[imp]

Can one get away with just re-shimming the carrier to bring the backlash into spec or is a rebuild a must?

Surprised by your question. Gear teeth rarely wear enough to increase clearance. Same for bearings properly preloaded. UNLESS foreign material becomes present, metal particles, OR the axle is run low on lubricant. That causes much higher temperatures, which alone can kill gears.

Re-shimming: Condition of the gear teeth faces would determine suitability for readjustment. If they are scored the least bit, chipped anywhere, or not generally shiny in appearance (satin-like surface), or burned, indicated by brown or even bluish-brown discoloration, they will make noise forever after.

As a general rule, when setting up a ring and pinion set, I like to go towards the high-end of backlash allowed, so long as contact pattern, especially on the drive side of the teeth, is acceptable. Unacceptable contact pattern would be if way off-center, especially out towards the outside diameter of the ring gear. FWIW, contact pattern is always observed on the teeth of the ring gear; pattern on the pinion teeth is largely meaningless. It should be understood that the contact pattern observed while manually turning the ring gear, while applying constraining force against rotation on the pinion (I use a rag wrapped around the yoke), covers only a small portion of the entire ring gear tooth, perhaps 30% of the entire area. Under load, due to deflection of the parts involved, as well as elastic compression of the tooth surfaces themselves, the entire tooth is under contact with the mating pinion teeth. imp

 

[TechGuru]

Surprised by your question. Gear teeth rarely wear enough to increase clearance. Same for bearings properly preloaded. UNLESS foreign material becomes present, metal particles, OR the axle is run low on lubricant. That causes much higher temperatures, which alone can kill gears.

Re-shimming: Condition of the gear teeth faces would determine suitability for readjustment. If they are scored the least bit, chipped anywhere, or not generally shiny in appearance (satin-like surface), or burned, indicated by brown or even bluish-brown discoloration, they will make noise forever after.

As a general rule, when setting up a ring and pinion set, I like to go towards the high-end of backlash allowed, so long as contact pattern, especially on the drive side of the teeth, is acceptable. Unacceptable contact pattern would be if way off-center, especially out towards the outside diameter of the ring gear. FWIW, contact pattern is always observed on the teeth of the ring gear; pattern on the pinion teeth is largely meaningless. It should be understood that the contact pattern observed while manually turning the ring gear, while applying constraining force against rotation on the pinion (I use a rag wrapped around the yoke), covers only a small portion of the entire ring gear tooth, perhaps 30% of the entire area. Under load, due to deflection of the parts involved, as well as elastic compression of the tooth surfaces themselves, the entire tooth is under contact with the mating pinion teeth. imp

I'm just getting desperate thus dumb, lol. It was quiet when I got it then it got loud suddenly after flooring it from a stop one time if that means anything... (squeezed the shims?) no idea.

I can't begin to consider a rebuild until late fall/winter. It's 100 outside and 120+ in the garage.

 

[imp]

I'm just getting desperate thus dumb, lol. It was quiet when I got it then it got loud suddenly after flooring it from a stop one time if that means anything... (squeezed the shims?) no idea.

I can't begin to consider a rebuild until late fall/winter. It's 100 outside and 120+ in the garage.

Ah! Sudden high load from a stop, if anything had gotten slightly out of whack, due to any one of a number of things, the critical alignment of the two gears was lost, resulting in gear hum. Squeezing shims won't make it. Cracked outer race of Differential Carrier bearing, either one, or pinion bearing, though that's much less likely. The torque applied to the diff carrier is driveshaft torque times
the gear ratio, can be several thousand foot-lbs, when transmission is in lower gears. If the hum is tolerable, not getting worse, and just a "singing" hum, no radical grinding-like sounds, you just might get by driving it with care for quite awhile. After all, some of the guys here say they have tolerated and driven with it for thousands of miles. OTOH, hum which develops gradually is the more likely type to allow use much longer than your type of problem, sudden gear noise.

Keep in mind that, if any gear teeth are chipped, or other hunks of metal debris is present, a corn-kernel sized one suddenly lodged between teeth can break off the ring gear tooth, which then lodges between the next two, which breaks another: like shucking corn off a cob. I've seen ring gears with half their teeth broken off, and one can only imagine the noise it made, and the stress it put on the center-section. Matter of fact, my buddy who raced a brand-new 1963-1/2 427 Galaxie, broke his center section clean in two! 9-inch Ford. imp

 

[TechGuru]

Ah! Sudden high load from a stop, if anything had gotten slightly out of whack, due to any one of a number of things, the critical alignment of the two gears was lost, resulting in gear hum. Squeezing shims won't make it. Cracked outer race of Differential Carrier bearing, either one, or pinion bearing, though that's much less likely. The torque applied to the diff carrier is driveshaft torque times
the gear ratio, can be several thousand foot-lbs, when transmission is in lower gears. If the hum is tolerable, not getting worse, and just a "singing" hum, no radical grinding-like sounds, you just might get by driving it with care for quite awhile. After all, some of the guys here say they have tolerated and driven with it for thousands of miles. OTOH, hum which develops gradually is the more likely type to allow use much longer than your type of problem, sudden gear noise.

Keep in mind that, if any gear teeth are chipped, or other hunks of metal debris is present, a corn-kernel sized one suddenly lodged between teeth can break off the ring gear tooth, which then lodges between the next two, which breaks another: like shucking corn off a cob. I've seen ring gears with half their teeth broken off, and one can only imagine the noise it made, and the stress it put on the center-section. Matter of fact, my buddy who raced a brand-new 1963-1/2 427 Galaxie, broke his center section clean in two! 9-inch Ford. imp

Mine is a loud gear noise like when you reverse with a manual transmission, louder under acceleration or up hills, quiet somewhat if let off the gas.

I have changed the oil and inspected the ring though the drain hole as much as I could. May have had some fine metal particles in the old oil, I cleaned the magnet on the fill plug which had a bit of build up on it. Gone about 9000 miles on it now I think (or 6000 I'd have to check) has not gotten any worse as far as I can tell.

 

[imp]

Mine is a loud gear noise like when you reverse with a manual transmission, louder under acceleration or up hills, quiet somewhat if let off the gas.

I have changed the oil and inspected the ring though the drain hole as much as I could. May have had some fine metal particles in the old oil, I cleaned the magnet on the fill plug which had a bit of build up on it. Gone about 9000 miles on it now I think (or 6000 I'd have to check) has not gotten any worse as far as I can tell.

Eventually, if my guess is right, the condition will gradually get worse, the noise will be frightening before any catastrophe happens. Guessing the "drive side" of the ring gear teeth are probably scored. The pic below shows how the pinion mates with the ring gear, in a 9-inch Ford set, all are essentially like this. If you look at the ring gear tooth shape to the right of the pinion, you will see that the tooth faces have different slopes. The wider tooth face is the "coast" side, the narrower, which is almost straight up and down, is the "drive" side. I understand removal of the cover of Explorer's solid-mounted center section is difficult. To really see the drive side faces, the surfaces have to be wiped clean of oil. Good teeth appear nice and shiny, mirror-like.

If it were me, and the noise is not too scary, I would keep driving it. imp