Recently, at about 170,000 miles, the transmission in my 2011 MKX (in automatic mode) shutters when it needs to down-shift, typically when the road changes from level to going up a hill at highway speeds (50 to 60 MPH +/-). It will shutter a bit when the vehicle speed begins to drop due to ascending the hill, then it will finally down-shift and pull up the hill with no further issues. If I move the shift lever rearward into “manual mode” before I reach the hill, and down-shift manually when I begin to ascend the hill, there is no shuttering and the transmission properly (and smoothly) down-shifts from 6th to 5th and pulls the vehicle up the hill with no problems. This issue has not occurred at lower speeds (35 to 45), only at higher speeds. There have been no issues with down-shifting when slowing down or stopping, and no issues up-shifting during acceleration. No Trouble codes have appeared so far.
When was the last time you had your tranny fluid changed?
Since it downshifts ok in manual mode, that’s good news. Problem seems likely to be the downshift decision. Maybe it can’t quite decide, wavering on what to do before committing. Main downshift decision inputs are vehicle speed, intake manifold vacuum, and engine rpm. If I had that problem I’d be checking if any of those are out of spec or not being read by the computer accurately. Good idea above about the transmission fluid. Esp if the trans fluid replacement is behind schedule, if I had the same problem, I’d start there, fresh fluid.
You mean that’s actually a “thing”. But on a serious note I would guess the torque converter is having trouble unlocking under load. I would see an independent transmission specialist, at least get a diagnosis and estimate. I have heard via the internet that a product such as this may help. I do not condone or endorse it, I have never used it. Also note the warning about Ford type F fluid. You’d have to check on that.
Thanks for the insights, much appreciated! The last time I had the oil changed, my mechanic checked the fluids and everything was okay (at least at proper levels) but I’ve never changed the tranny fluid. I bought the car with 130k miles on it and I’ve put 40k on it to date. The torque converter sounds like the culprit to me, and that sounds like about the most expensive fix too (my luck)! But I’ll take your advice and locate a transmission specialist around here and have them check it out. I’m hesitant to take it to a Ford / Lincoln dealer because I doubt they would say anything other than: #1 - Can’t replicate problem… or: #2 - Yep, it needs a new tranny… I’m also hesitant to use the additive, simply because of the “Ford” warning! It’s got enough problems without ME adding to them! I’ll post updates.
It doesn’t use Ford type F fluid. This trans uses Mercon LV. Plus, I don’t think it has a high mounted dipstick that would allow you to easily add this product to the trans.
Get the fluid and filter changed, not flushed, changed.
Just changing the transmission fluid and filter serves absolutely no benefit.
So don’t bother wasting your money.
Tester
I disagree.
A fluid change will only drain a bit more than half of all the fluid. This is a 6R80 transmission. Dropping the pa will drain 8 of the 13 quarts inside it. Dropping the pan allows the filter to be changed and the pan cleaned to remove that 170K mile debris build-up. The resulting mix of old and new fluid is still better than no changing it at all.
A flush will swap all the fluid getting all the contaminants in solution in the oil out the debris in the pan an filter will remain.
That’s why I believe the first service should be a pan drop and change rather than a flush and this site agrees.
I agree with mustangman with that mileage. It would be like doing an oil change and not changing the filter.
Show me where I typed don’t drop the pan or change the filter?
Because when you also do that, it can be determined if it’s even worth flushing the transmission fluid.
Tester
I don’t think there’s one simple answer to the question.
Yes, when addressing a performance concern I like to see what’s in the pan. But there’s also a cost concern. Take a typical family truckster like a Chevy Tahoe. Labor to R&R the trans pan is something like 2.2 or 2.4 hours. At today’s labor rates, a simple pan service will be $600. If I can do a fluid exchange for half that much, that’s an attractive option.
And I’m not even talking about the Ford Transit vans that have a 5.4 hour trans pan service time.
Agree, you didn’t type “don’t drop the pan.” But it seems pretty clear from the statement above, especially the “don’t bother wasting your money part”…
That’s because I’ve seem so many people over the years just do a drain and fill on high mileage transmissions only to have the transmission fail a short time later.
Because the new transmission fluid with its detergents starts dislodging debris throughout the transmission.
Then they bring the vehicle to me to do a flush, but it’s too late.
Ergo, waste of money.
Tester
If the fluid change is not too expensive, you are only out maybe $200. And at least the technician can see in the pan and give the bad news to the owner. Or if it doesn’t look too bad, change it.
The 6R80 is pretty robust and quite expensive to replace. I’d spend the money for a fluid and filter chnage and take that chance.
If I was a shop owner, I might not advise that path since there is so much “you service it, you own it from here on out” out there.
BINGO!
Or in other words, do the job right.
Tester
Best approach seems to depend on the P& L fees for a flush-machine approach vs a pan-drop approach on this vehicle. Anybody know what those fees would be?