I'm hopeful Mark will see this and have some insight and suggestions as I address what I believe is signs my 4R100 is failing.

The issue: when I reach 37-40mph I have a new sound which I believe is the transmission. It sounds like a flat spot on a tire, or the sound tires make when they leave the sticker on them. The cadence of the sound is slower than the rotation of the wheels.

If I let off the accelerator, the sound stops, as soon as I add load by pressing the accelerator the sound returns. If I shift to Neutral the sound is gone.

If I coast at any speed the sound is gone. It is only audible when under load at speeds above 37-40 mph. The cadence does increase as I speed up, but it doesn't sound as fast as the motor is turning (~1900 rpm's).

I monitor the truck with torque pro using the PIDs defined here on FTE. I can see lock-up in 3rd and the shift to overdrive. When in lock-up, I see 1-7rpm TCSlip.

Watching transmission temp as reported by torque, the hottest I see is 183* pulling an enclosed 6x12 @ 75 mph. Ambient temp is 95*. Excursion currently has 240k miles on the clock.

This sound was first heard by my wife two weeks ago. I thought I had tire issues and they needed to be rotated. The sound is still present, and now identified only when the truck is in drive, and under load, regardless of me pulling a trailer.

Yesterday on my 500 mile trip, the truck hiccuped several times which I believe was around the time I was either moving in or out of overdrive. Detsils in a different thread: https://www.ford-trucks.com/forums/1397139-truck-stutters-on-road-after-long-drive-help-still-driving.html#post15636354

Anyway, I've looked at all culprits and can't find anything with the motor, or electrical system. I can't get to a transmission shop until Monday, and won't have my AE until I get home Sunday night. I have a 500 mile run tomorrow.

I checked the transmission fluid and it's at a good level, pink, and doesn't have a bad smell.

Any suggestions or thoughts?

 

Im no tranny expert but ill throw my 2cents
No foul smell from the oil or burnt looking, means your tranny is still salvageable . Does it sound like a low pitched humming sound? If so seems your torque converter is on its way out. You should be fine, just dont go smashing on the throttle on the stop lights, that would surely make things worst.

 

How did you reach this conclusion? Maybe I missed something, but I don't see anything in the original post that would let me determine anything. What did you see that I missed?

 

"It sounds like a flat spot on a tire"
Maybe let me to believe it sounded like an MT tire with cuppin problem, im just throwing it out there. When a tc is starting to fail you get this low pitch humming sound.

 

When my TC started going out it sounded like marbles in a metal coffee can rolling around. If its your TC you will likely be ok so long as it hasnt grenaded like mine did. I didnt realize what was going on until it was too late and my trans temps hit 250+ one night.

So long as metal hasnt gone through your transmission like in mine u can get away with replacing the just TC.

 

I'm not sure I have a transmission issue. That's my problem. I have a noise that I've pinned down to a specific repeatable process, but I don't know if that's means transmission or something else.

The sound reminds me of a tire with a flat spot, or the sound new tires make when the paper tag is left on the tread.

Anyone ever hear something like that? Temps and TC slip are all normal.

 

I spent nearly 2 weeks tracking down a sound i couldn't figure out. Mine didnt sound like that. But i discovered finally that my transfer case was engaged even though I had no 4x4 indicated on my dash. The plug had come loose from the esof motor and my hubs were not engaged so it never felt like it was in 4x4. I have no clue how the tcase got engaged. I doubt your having the same issue, but the check is simple, climb underneath w truck off and see if your front drive shaft will turn. If it doesnt, the tcase is engaged.

 

Thank you, I'll try that out.

To confirm, hubs unlocked and Transfer Case disengaged, spin the front drive shaft. I'll check it out.

 

I am not a transmission expert. About 35mph is when my TC locks up (one of my tunes locks it and keeps it locked above that speed).

Perhaps that is your problem, going into TC lockup? Can you feel it "shift" into lockup, or does the transmission seem to stay in a "lower gear"?

I have a difficult time telling TC lockup from gear shifts, unless looking at TorquePro with the gear number display, so that's how I described it- with quotes

 

Well an update after anothe 550 miles today. The sound is still there and I have two videos where you can hear the noise. Please note I held my iPhone at 35-40mph so there is some wind noise.

A few notes: I check all the tires and no cupping. The air pressure is equal in all 4 tires. The sound is very consistent and easy to replicate.

Videos:

 

Mark, I guess nothing here points to the 4R100 as an issue? I'm heading to my local Ford Mechanic this morning to see if he has any insight. I firmly feel it's driveline as the sound is only audible when the driveline is under load.

It's more pronounced in the rear and with my wife's help, we think drivers rear.
Just wanted to check with you as the authority on the 4r100

 

I'm not very good at diagnosing noises, especially ones that I can't hear, but nothing here stands out as pointing towards the transmission.

 

Have you checked the UJoints?

Block the wheels and crawl under there and give the driveshaft a good yank and see if there's any u-joint play.

While you're under there, it would be a good time to make sure the transfer case and rear end fluid is good too.

Also, I think someone suggested that you make sure the front DS spins freely. That would be good to do as well...

Do you get any kind of clunk when just starting off or going between drive and reverse?

 

First thank you Mark for visiting this thread and commenting. I completely understand your comments, the good news is nothing posted has sparked your interest as a transmission issue.

We are moving past the transmission and to the rear differential.

Yesterday, I confirmed the T-Case was working correctly and the front drive shaft isn't spinning in 2wd mode. I didn't feel any movement in the U-Joints, but that was before the last 500 miles of Sunday.

A video I was able to make today, leads me to a broken or damaged tooth on the Ring/Pinion in the rear end.


My Ford mechanic will give it review and a run with IDS to see if anything is uncovered. I had a whine from the rear end that we've known about and planned to fix. I'm wondering if that time is now.

Today we'll pull the rear diff inspection cover and check for damage. If so, it's a complete rebuild with a Eaton Trutrac diff and new gears, bearings, etc.. Not cheap but I'm ready for the worst.

 

The driveshaft/u-joints would be very good to check. I don't believe you can check them with the driveshaft installed in the truck. I've seen some REALLY bad u-joints that didn't feel bad at all until the driveshaft was removed. Then it was obvious that they were bad.