2019 GT Premium Convertible driveline issue

Hey guys!
I am an old Mustang guy (All Foxes and one 1970 sharknose). Retired Army.

After years and years of deliberation and saving, I have purchased an incredibly low mile 2019 GT Premium Vert in Ruby Red. To me, the cars color and interior is absolutely beautiful.
It is a 10R80 car.
It has 22,000 miles on it.

Minor Necessary Info: Vehicle was sold to me under the pretense and advertisement of a clean Carfax, no accidents. An autocheck return a week later showed a "minor accident". I paid the vehicle off in full at time of purchase. VA law may permit me to force them to take the vehicle back, but I would prefer not to do this as the combination is precisely what I was looking for.

The Problem:

When in Normal or Sport+ at approximately 45-70mph, and at higher speeds in more aggressive throttle regimes, (75%-100%) I am getting a "clunk" that sometimes presents as a "shunting" noise around the 3rd to 4th change that seems to originate in the rear end and slam into the transmission tunnel. This is sometimes accompanied by a driveline "wobble" or "vibration" of about .5-1.5 seconds.
The vehicle also feels "loose" at the rear end on aggressive braking and is leading me to believe the rear geometry is not square on weight transfer. It seems to pull straight on throttle, then "float" on deceleration or hard braking.

I do have my mechanic looking at it right now, actually, so I will probably know for sure soon, but just in case they turn up nothing, what do you guys think this might be?
Any other S550 owners run into this on their 10R80 cars?

It's weird because sometimes I can drive it around all day and it won't do it, then all of a sudden it does it all day in the specified conditions.

Any advice is greatly appreciated.

Thank you!

LILCBRA said:

Welcome to the site!

I can't help much with anything newer like this, but I'm sure someone will be along soon to give you some ideas.

And, as will surely be requested by someone - be sure to post pics of your ride! Everyone here loves pics!

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I will do so indeed! Thanks for the welcome, it is appreciated!

Here is a nice side profile of it.

Performance shop did the diagnosis with no charge, so that was nice.
All of the bushings and undercarriage looks spotless and well-representative of a 22,000 mile car.
They are not specialists on the 10R80 so told me a guy at a Ford dealership in town definitely is, so that's my next stop.
They think it's probably a shift instruction or solenoid or the like.

90sickfox said:

My 2019 10r80 had a bump sometimes when decelerating and easing back in the throttle. I bought my car brand new from Ford and it did it from day 1 until I sold it with just under 60k miles. The Ford dealer can flash the adaptive learning strategy for the tramsmission and it will help. I learned to let off the gas pedal completely when coasting and gave the car a split second to get its act together between 3-4 and 4-5. Once i learned the car it rarely happened. At fist i though the transmission ir rear was trying to fall out. Smh. Drove several other new cars ( on test drives ) and issue was there with all of them. Dealer checked mine out, reflashed it but said it was normal.

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This is helpful in perspective, thank you.

For me it is right at the 75%-100% throttle at that 3-4 or 4-5 shift.
It shunts hard *knockknockknock* like it's beating on the tunnel, then rarely has a brief vibration following it.

After the reset yesterday I drove it around today and it seems to be much much softer on that 3-4 shift.
The knock I have heard since is subtle. More like a door closing gently than someone smacking a drum. No vibration.

I haven't kicked it too hard since.

Thanks again for the feedback, it is appreciated!

I Bleed Ford Blue said:

I have the 10R80 in my 23 mach 1, ford tuning/shift strategies suck on the 10R80. That trans was jointly developed with GM and their version is perfect. Instead of chasing your tail trying to get ford to make it right, which will never happen, get a custom tune if for no other reason than to improve the shifting.
I went with https://wengerdperformance.com/ they come highly recommended over on the other mustang forum I'm on.

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Appreciate the heads up.
The issue I'm having sounds pretty "mechanical" and the shift adaptations have been zeroed out and reset already.
It literally sounds like someone whacking the transmission tunnel with a ball peen hammer 2-3 times rapidly.
The car is still under warranty so it is at Ford right now.
If they can't figure it out/repair it, I will simply seek out an individual tuner like you suggested.

My prior understanding is that these transmissions are pretty good mechanically but that Ford included some modes/instructions that GM does not.
So it's cool that that echoes your experience here.

Again, I appreciate the heads up!

Update:

Dealer says the tech struggled to find it at first, could not repeat on drive.
Last attempt to repeat showed the symptom.
When it happened as described in my OP, he immediately suspected some driveshaft issue.
When looking at the driveshaft yoke he said at the U-joint it had signs of wear but you had to look close and put it under pressure.

I kind of find this odd. Has any other wrench had this sort of thing happen?

Where the driveshaft U-joints misalign in only one small gearchange window?

I guess I could hypothetically see it, but it seems odd.

When I get it back next week I will immediately try to reproduce it and try to remember to post the results here.

Update as stated:

Car no longer knocks three times on the transmission tunnel. I've driven it for several days through all throttle inputs and modes.

Technician stated that the wear on the yoke itself was so bad the u-joint cups could float around and grease was flung everywhere.
When torqued on it would "rock off of centerline" causing driveline stress and popping. The occasional wobble being a result of being out of balance.

Calling it good.