In 5th and 6th gear under light throttle I get a feeling in the pedal and seats that feels like driving over a rumble strip, sort of a shudder/vibration. This thread describes exactly what I experience:

https://www.f150ecoboost.net/threads/16-rumble-strip-shudder-vibration-when-accelerating.80261/

Lots of people in there saying they did a transmission flush - I thought that was generally a bad idea? I have 125k miles and don't want to ferk it up worse than it already is.

What say you oh wise auto board?

I've driven a few of these ( company trucks).

I think it's a torque converter shudder. Or something related to lock up.

Engaging 4wd doesn't change any thing.

U joints look and feel ok. Mounts ok. Pinion angles ok. No looseness in front or rear differential housing mounting points.

Not a misfire. Only on tip in throttle ( which is typical engage and disengage of tc clutch).

Happens in 6th no matter temp. Occasionally 5th.


Edit:

Options are to do fluid exchanges to remove old fluid or swap TC.

If the TC clutch is damaged a fluid exchange would not do much.

Yeah I'm reading a fair bit about torque converter shudder. Seems like a fluid exchange can help but in the end might require a new torque converter eventually.

If the issue is related to fluid condition a fluid exchange would be obvious.

But if the clutch is damaged it may not help much if at all.

GarlandAg2012 said:

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Yeah I'm reading a fair bit about torque converter shudder. Seems like a fluid exchange can help but in the end might require a new torque converter eventually.

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Are you at 125K on original trans fluid? If so change the fluid and filter and see what happens.

Ford says to change at 150K which is preposterous. I've seen anywhere from 30K-60K intervals suggested. I waited until 81K but I'll likely do every 60K from here on out.

I have a 2015 F150 5.0 4x4 and I just changed all the drivetrain fluids at 81K (Trans, Front Diff, Rear Diff and Transfer Case). It definitely smoothed out my shifting.

Good to know. Was just going to do transmission but I will have them do the rest of the drivetrain as well. Have you had the 5-4 downshift issue? There's a TSB for it but it doesn't happen often in mine.

GarlandAg2012 said:

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Good to know. Was just going to do transmission but I will have them do the rest of the drivetrain as well. Have you had the 5-4 downshift issue? There's a TSB for it but it doesn't happen often in mine.

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I haven't noticed the 5-4 downshift issue in mine. We were in the mountains in Colorado back in July though and mine was shifting rough on the 2-3 upshift/downshift but only in sport mode when going through the passes. I could notice it just barely in normal mode but once I changed all the fluids I haven't had it happen again (knock on wood).

Sidebar --- I really like the FordTechMakuloco guy on youtube. His yankee accent is annoying but his Ford expertise is spot on. I was going to change all the fluids myself but it seemed like a painful and time consuming process so I punted to a shop.

Anyone got a shop recommendation in Dallas? Here are my two experiences from today trying to get it taken care of:

Independent shop I trust a decent amount: We can do a drain and fill but you probably need a full fluid exchange, we don't have the machine. Sorry but don't want you to waste your money

Ford Dealership: With 125k miles I wouldn't change any fluid. We need to diagnose to see what's really wrong. Diagnostic is $119 to start.

Feeling frustrated at getting two polar opposite answers.

You can get by without a flush machine.

You do a drain and refill about 3-4 times with about 5-10 minutes of going through gears on lift or stands. Then change filter and top off.

Went to TX Transmission Repair in Dallas this afternoon. Nice guy and good service but wanted to do a full rebuild for $2850. I guess it's possible I will end up there but I still want to try the fluid first. Ag for Life sent me a rec, I will try them next I guess.

Is it only at certain RPM/gear/speed?

We had something similar in our work 2015 and it turned out to be an issue with the 4x4 trying to engage due to some sort of compression issue via the electronical signal.

Some stuff about it on YouTube's.

Just my opinion, but I wouldn't do a flush, just do a drain and fill.

GarlandAg2012 said:

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Anyone got a shop recommendation in Dallas? Here are my two experiences from today trying to get it taken care of:

Independent shop I trust a decent amount: We can do a drain and fill but you probably need a full fluid exchange, we don't have the machine. Sorry but don't want you to waste your money

Ford Dealership: With 125k miles I wouldn't change any fluid. We need to diagnose to see what's really wrong. Diagnostic is $119 to start.

Feeling frustrated at getting two polar opposite answers.

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Just tell the dealership to shut up and do the fluid change. Of course they want to throw parts at it for an eternity and keep ringing up the $$$.