'02 RWD 8.8 Howling Sound ... how much time do I have left??

[FordRangerFan777]

In the last 60 ish days I've noticed a howling sound coming from the rear of the truck. It's getting worse. How much time do I have left before it becomes a catastrophic failure? And how bad can that be if that happens?

Background (context): Around July (2023) I noticed some fluid on my tailgate & rear bumper. In November (2023) I learned this was an indication of a pinion seal going bad. I confirmed the seal was going bad and replaced it (in November). When I did, I checked the fluid and it was a little low (only took about a quart of fluid), but didn't seem low enough to cause concern. I did notice some metal on the bottom of the fill plug. About 60 ish days ago, I began hearing a howling sound from the rear of the truck and in the last week or so it's gotten worse. The truck has ~225,000 on it but the rear axle is a junk yard axle. When I bought the truck, I saw the paint markings on the diff cover and the gear ratio is different than stock for my truck. When I bought the truck (with about 135,000 miles), I drained and put new fluid in the diff. I also noticed metal on the fill plug then too.

I checked the fluid level last week and it was full. Right now I drive about 200 miles / week. I have plans to do an explorer axle swap but had not planned on doing that for another few months.

Couple questions.
1. Am I right to think it's the rear axle causing the sound? Or am I way off? And if so, what do I do to confirm the source of the sound?
2. If it is the rear axle, is there anything I can check? Either what I have already checked or something else?

 

[superj]

When you drive, do some slow S turns back and forth on a straight road and see if the sound is louder when turning one way. If so, its a wheel bearing, not one in the diff

 

[02FX4]

Chances are high that it's your pinion/ring gears. The fastest way to analyze is pull the diff cover and capture the fluid in a smooth bottom catch pan and examine for metal residue. Then check the gear mesh surface and backlash. That will be more conclusive that anything else. Depending on whether or not it's an open/LS or helical diff also means you may or may not have to swap out for new parts in the guts as well. Open diffs do pretty well under pinion/ring wear.

 

[FordRangerFan777]

When you drive, do some slow S turns back and forth on a straight road and see if the sound is louder when turning one way. If so, its a wheel bearing, not one in the diff

That's a great idea. I haven't done that but will try it and see if there is a difference in sound.

Chances are high that it's your pinion/ring gears. The fastest way to analyze is pull the diff cover and capture the fluid in a smooth bottom catch pan and examine for metal residue. Then check the gear mesh surface and backlash. That will be more conclusive that anything else. Depending on whether or not it's an open/LS or helical diff also means you may or may not have to swap out for new parts in the guts as well. Open diffs do pretty well under pinion/ring wear.

This makes sense and is kinda what I was thinking but not hoping for. It's an open diff. When I capture the fluid, what types of things should I be looking for? Am I just checking to see if it has metal in it? Or am I looking for chunks of metal? Any insight would be helpful.

My assumption when checking backlash / gear pattern, it's probably easier with the axle shafts pulled? Or am I over thinking it?

 

[02FX4]

That's a great idea. I haven't done that but will try it and see if there is a difference in sound.



This makes sense and is kinda what I was thinking but not hoping for. It's an open diff. When I capture the fluid, what types of things should I be looking for? Am I just checking to see if it has metal in it? Or am I looking for chunks of metal? Any insight would be helpful.

My assumption when checking backlash / gear pattern, it's probably easier with the axle shafts pulled? Or am I over thinking it?

You can check backlash if the wheels are off the ground (tires off) fairly easy (though axles out would be easiest) and as for "chunks" of metal in your gear oil, that is a sure sign a tear-down/replace job is at hand because broken ring/pinion/spiders is the source. If there is glitter, it depends on your wear pattern and if your spiders are tight. Some glitter is expected over time, but You'd have to clean everything with brake clean and then paint your gear mesh to see the wear pattern between ring and pinion and recheck backlash. Anything obvious should stand out like a sore thumb.

 

[02FX4]

That's a great idea. I haven't done that but will try it and see if there is a difference in sound.



This makes sense and is kinda what I was thinking but not hoping for. It's an open diff. When I capture the fluid, what types of things should I be looking for? Am I just checking to see if it has metal in it? Or am I looking for chunks of metal? Any insight would be helpful.

My assumption when checking backlash / gear pattern, it's probably easier with the axle shafts pulled? Or am I over thinking it?

Also, I'vee seen instances where the pinion nut has loosened over time and the pinion seal is worn out and leaking oil. Sometimes you can get away with simply re-torqueing your pinion nut and replacing the pinion seal and you're go to go for another 20k miles+.

 

[FordRangerFan777]

You can check backlash if the wheels are off the ground (tires off) fairly easy (though axles out would be easiest) and as for "chunks" of metal in your gear oil, that is a sure sign a tear-down/replace job is at hand because broken ring/pinion/spiders is the source. If there is glitter, it depends on your wear pattern and if your spiders are tight. Some glitter is expected over time, but You'd have to clean everything with brake clean and then paint your gear mesh to see the wear pattern between ring and pinion and recheck backlash. Anything obvious should stand out like a sore thumb.

Also, I'vee seen instances where the pinion nut has loosened over time and the pinion seal is worn out and leaking oil. Sometimes you can get away with simply re-torqueing your pinion nut and replacing the pinion seal and you're go to go for another 20k miles+.

Thank you! This makes a lot of sense. I checked out a few videos and realized when I replaced the pinion seal, I just put on the pinion nut and never torqued it. When I dig into it, I'll pull the pinion nut and torque correctly. A video I watched said they are only to be used one time. How necessary is it for me to get a new one?

 

[02FX4]

Thank you! This makes a lot of sense. I checked out a few videos and realized when I replaced the pinion seal, I just put on the pinion nut and never torqued it. When I dig into it, I'll pull the pinion nut and torque correctly. A video I watched said they are only to be used one time. How necessary is it for me to get a new one?

Yes, but you'll be ok using the old one one more time. People get a bit too anal about it, but I've done it and ever other backyard mechanic has as well. The most important thing is to get the pinion drag (pre-load) set properly. It's like 18-22 inch lbs.

 

[FordRangerFan777]

Sounds good! Thank you. And that's the answer I was hoping to hear.

 

[Ramcharger90]

3. 2. 1.

 

[sgtsandman]

If it's the pinion that is howling, it's going to be a real roll of the dice on if you can just tighten the nut and be good. Look at the fluid first. If there is a lot of sparkels in the oil, I would look at replacing the pinion bearings. But Murphy's Law has a history of bitting me in the but at the least convienent time. So, I may be just being overly cautious.

 

[02FX4]

If it's the pinion that is howling, it's going to be a real roll of the dice on if you can just tighten the nut and be good. Look at the fluid first. If there is a lot of sparkels in the oil, I would look at replacing the pinion bearings. But Murphy's Law has a history of bitting me in the but at the least convienent time. So, I may be just being overly cautious.

Chances are, if there is a ton of glitter, it would be more than just bearings and a new ring and pinion may be needed as well. If bearings are too far gone they quickly wear the ring and pinion from misalignment.