2017 lurching in and out of 8th gear after long drive cycle

teamster

Member
Joined
Nov 17, 2021
Posts
45
Reaction score
38
Location
Left Coast
Hey folks, I have a weird issue that has come up a few times now, so it's time to do some digging. I've searched through as best I can and can't find anything that speaks to this specific issue.

After about 8-9hrs of driving, of which about 5-6hrs is uninterrupted engine running time (i.e. straight interstate driving, no auto-off or other engine stops), my 2017 transmission starts to run into power and shifting issues going in and out of 8th gear.

Context:
Issue only appears when vehicle has been operating without break for several hours at highway speeds. Shorter interstate trips of less than 4-5hrs does not seem to induce the issue. Long trips with interruptions where the vehicle is power cycled seem to forestall the issue. Issue only seems to present after segments of 4-5hrs without break.

Behavior:
Truck will be driving steadily at 70-75mph, and accelerator is depressed (e.g. to pass a vehicle). The truck pauses a moment before hard shifting down into or past 8th, with a distinct "bump" or lurch feeling before power is applied. The acceleration is not even, and is noticeably reduced compared to regular acceleration. The bump/lurch can be replicated by manually shifting in or out of 8th gear, both up into 9th and down into 7th.

Temporary Resolution:
Stopping the vehicle and cycling the ignition with a short (less than ten minutes) break before resuming operation seems to resolve the issue. This issue has come up twice, both times in the last two weeks.

Any thoughts on what this might be? The fact that I can get temporary resolution by cycling the ignition suggests to me that it's likely a software issue. This is a frustrating issue to try to troubleshoot because it only comes up after several hours of uninterrupted driving.
 

smurfslayer

Be vewwy, vewwy quiet. We’re hunting sasquatch77
Joined
Dec 16, 2016
Posts
12,533
Reaction score
15,010
Not that this is a fix, but if you change to sport does the behavior change at all? I’d think about doing the transmission re-learn process and retest as it sounds like this would be an exceedingly frustrating issue to track down.

If you don’t have FORSCAN, get it and the adapter and pull your DTC to see if that sheds any light on things.

The 2017 programming was not brilliant. As delivered, my truck would refuse to downshift at highway speeds - 50 or over. Once in 10th, in normal mode, unless it went under 50 and I floored it, she wouldn’t do it. I got revised TCM programming that addressed it rather well. I’d consider a stealership visit for that - I think there’s a TSB for it - rough shifting or erratic shifting.
 
OP
OP
teamster

teamster

Member
Joined
Nov 17, 2021
Posts
45
Reaction score
38
Location
Left Coast
Yeah, I booked an appointment at the dealership - closest date is October 3rd. I'll grab the DTCs tomorrow morning and report back, see if anything comes up.
Not that this is a fix, but if you change to sport does the behavior change at all? I’d think about doing the transmission re-learn process and retest as it sounds like this would be an exceedingly frustrating issue to track down.
Great idea to check if switching to Sport changes things. Next time this comes up I'll give it a shot.
 

smurfslayer

Be vewwy, vewwy quiet. We’re hunting sasquatch77
Joined
Dec 16, 2016
Posts
12,533
Reaction score
15,010
Yeah I can say I’ve not had that, but only had about a dozen or so driving sessions that long. It sounds really odd. I would definitely push for the most current TCM programming and make sure you verbally or in writing voice the complaint - My truck has erratic and sometimes harsh shifting, in addition to any other details of your specific problems. The reason is that Ford will only update the TCM code if there is an actual customer complaint AND the complaint matches the TCM. If you don’t raise the complaint and only say ‘please update the TCM’ they will connect and report back “TCM code is current” or some similar ‘soft language’. It took me 2 visits to get the update because they kept hooking up the scanner and reporting back the code was current. It was not MOST current.

I understand this but it is one of those frustrating policies that underwhelms customers.

Good luck.
 
OP
OP
teamster

teamster

Member
Joined
Nov 17, 2021
Posts
45
Reaction score
38
Location
Left Coast
So I just picked my truck up from the dealership, having provided them all these details. They flashed the TCM, but gave me a *very* hard time about the modifications I've made to the truck. Specifically, they called out the ADD intercooler I installed, claiming that it is blocking the transmission and A/C radiator and likely caused the issues due to boiling off the fluids. The advisor even said "I'm surprised you even have working A/C."

Now, this doesn't make a lot of sense to me. Transmission overheating was my top hunch, and as I experienced the issue while driving, I checked the gauges and saw only normal temps across the board. The A/C also works like a charm, and has never struggled to cool the cabin.

The advisor also stated that I "must have a tune or other software loaded" because the technician was having an issue accessing the PCM software. I have never installed any tunes on my truck, though I have made changes in ForSCAN. Is this nonsense, or is there something I should look further into?

Anyway, here's hoping that the new TCM software fixes the issue. I won't know till my next long road trip, but I'll update with anything I find out.
 

djevox

Active Member
Joined
Sep 24, 2022
Posts
100
Reaction score
177
Location
MD
So I just picked my truck up from the dealership, having provided them all these details. They flashed the TCM, but gave me a *very* hard time about the modifications I've made to the truck. Specifically, they called out the ADD intercooler I installed, claiming that it is blocking the transmission and A/C radiator and likely caused the issues due to boiling off the fluids. The advisor even said "I'm surprised you even have working A/C."

Now, this doesn't make a lot of sense to me. Transmission overheating was my top hunch, and as I experienced the issue while driving, I checked the gauges and saw only normal temps across the board. The A/C also works like a charm, and has never struggled to cool the cabin.

The advisor also stated that I "must have a tune or other software loaded" because the technician was having an issue accessing the PCM software. I have never installed any tunes on my truck, though I have made changes in ForSCAN. Is this nonsense, or is there something I should look further into?

Anyway, here's hoping that the new TCM software fixes the issue. I won't know till my next long road trip, but I'll update with anything I find out.
Any time there’s a modification anywhere near related to a condition, a dealer will use it as an excuse. I’m not saying all of the dealers do it, but it’s an easy out where the dealer can point a finger at your mods and not have to back up their claims with any evidence.
 
OP
OP
teamster

teamster

Member
Joined
Nov 17, 2021
Posts
45
Reaction score
38
Location
Left Coast
Any time there’s a modification anywhere near related to a condition, a dealer will use it as an excuse. I’m not saying all of the dealers do it, but it’s an easy out where the dealer can point a finger at your mods and not have to back up their claims with any evidence.
Yeah, that's my thought too. It was somewhat surprising in this situation. In my past experiences with this same dealer, they were curious about the various mods at worst, and more often were enthusiastic about them.
 
Top