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Truck jumps like I got hit after coming to complete stop.

ryanc111

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Just some clarification of the auxiliary pump and its role/purpose


Screenshot_20220713-171209_OneDrive.jpg
Great information, thanks. While I was told replacing the 'transmission aux pump' fixed the issue I for the life of me couldn't figure out why my transmission even had a pump in it. This makes a ton of sense now.

And since my fix was done a couple of months ago I have had zero issues since.
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Snakebitten

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Yea, most of us never considered all the components of a normal ICE truck that need to be addressed if the engine was off for lengthy amounts of time.

The Powerboost is remarkably electric.
The Air Conditioner has an electric compressor. The brakes and other components that rely on vacuum get vacuum from electric pump. Coolant loop for Hybrid battery and multiple converters uses electric water pump. And as pointed out in the image, the transmission line pressure is maintained with an electric transmission fluid pump.

It's a dauntingly complex vehicle that looks like a plain old F150. :)
 

Viper

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Are you describing the truck not downshifting while the engine is running?
Or has the truck already switched to EV mode while it's decelerating, yet not downshifting?
yes and even though it will switch to EV while coming to a stop it is still in 8'th gear. I have even put it in park then back to drive. When I do that it will show 1'st gear until I proceed to take off it switches back to 8'th gear and will go REAL slow for 10-20 feet then a loud bang as it down shifts to 1'st or 3'rd and feeling like I got rear ended
 

Snakebitten

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yes and even though it will switch to EV while coming to a stop it is still in 8'th gear. I have even put it in park then back to drive. When I do that it will show 1'st gear until I proceed to take off it switches back to 8'th gear and will go REAL slow for 10-20 feet then a loud bang as it down shifts to 1'st or 3'rd and feeling like I got rear ended
I'm no automotive technician but it wouldn't be out context that a faulty auxiliary pump is a role player in your symptoms.
 

Viper

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Seems to be a known problem after reading this thread
 

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Singblaze

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Dropped my truck off on Monday morning - got an update this afternoon (Wednesday). They replaced a thermostat on my transmission (wasn't ever running hot - but maybe something they saw on their end or replaced if they were servicing that area versus putting old back in). That wasn't the main cause of the issue, it was the aux transmission pump that wasn't working properly, which is causing the jumping/banging/lurching that happens on occasion a few seconds after stopping in electric mode. Part is on national backorder - said may have it within 2 weeks if lucky, but I could continue to drive the truck in the meantime until it comes in, so I'll pick up tomorrow. Just sharing for those that have the same issue or will have same issue - someone else in this thread posted it was their aux transmission pump and that is what mine was as well.
I really appreciate your update. I have to wait until Aug 8th. for service
 

TINY5521

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2021 F-150 Limited Powerboost build in July 2021 (late Job 1 truck), just under 8k miles. This issue just started, I'll be in normal drive mode and when I come to a complete stop, within 2-3 seconds I get a bump feeling like I got rear ended and if you don't have your foot smashing the brake pedal, the truck will jump forward a bit, it's quite scary and really gets your attention. I tried putting my truck into sport mode the last two days and it happened less (updating this section of my post), I thought it stopped it but it happened again in sport mode. I'm now trying tow mode to see if I can keep it from happening until resolved. (update - seems to not happen at all in tow mode, if engine is running when I brake and stop, doesn't happen. I can make it happen just backing up out of garage in ev mode and putting into drive and holding brake - I don't have brake hold on and never use this feature as it's hard to ease up a couple inches in electric mode when pulling in garage).

Could this be a software change from a recent OTA update? I just went from 2.8.1 to 2.8.2 (actually happened while we were visiting family and updated on way home as I got the bluecruise message on ford app and finally got to use it on the way home). Since that update, this has happened each time I drive it. UPDATE - now on 2.8.3 and still have issue, so if software related it didn't resolve in next release.

I have a video of it doing the issue in my driveway - not sure if it will pay here if I attach, but attaching in case its viewable. It happens 7 seconds after I go from reverse to drive. You can hear the clunk and if you look closely, you can see the truck jump (i have the brake pushed down hard).

The same type of thing just started with my 2021 Powerboost. Sitting a a stop, after about 3-10 seconds, the truck lunges forward with a loud bang, almost like getting rear ended. I also have a aux trans pump failure code that has come up as well. I'll be heading to the dealer tomorrow for them to check out.
 

bball3

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Not sure if others are experiencing this, but Ford is now saying they have no idea when they can get the part in. I’ve been without my truck for 3w while they troubleshoot/order parts already. In a rental right now while they try and figure out how long this is going to take.
 
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Infidex

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The same type of thing just started with my 2021 Powerboost. Sitting a a stop, after about 3-10 seconds, the truck lunges forward with a loud bang, almost like getting rear ended. I also have a aux trans pump failure code that has come up as well. I'll be heading to the dealer tomorrow for them to check out.
Would get in soon as you can, it's a long wait for the part. I'm still waiting, think I'm going on 6 weeks.
 
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Infidex

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Not sure if others are experiencing this, but Ford is now saying they have no idea when they can get the part in. I’ve been without my truck for 3w while they troubleshoot/order parts already. In a rental right now while they try and figure out how long this is going to take.

I'm at about week 6. When I first had it, no code or check engine light. They allowed me to keep driving it and Ford claimed it won't hurt anything. I've been driving it in Tow mode as the issue isn't there when the engine is running as the aux pump isn't needed then. My check engine light finally came on after about 500 miles of driving and it realizing that the pump is not working. I actually called to check on status and they said they had the part, dropped truck off and got call that they didn't have the part, so I have it back again and still waiting. Ford has these parts as they are building trucks with them, just prioritizing what they have on new builds versus servicing us with issues. This aux pump is going out more and more for folks, even seen another forum where someone had the issue and dealer is claiming its not covered as part of drivetrain warranty because it's bolted on the outside.
 

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Infidex

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I really appreciate your update. I have to wait until Aug 8th. for service
No problem, good luck. I just started on week 6 of waiting for a part. Dealer ordered it and gave truck back, said it's fine to drive until it comes in. Keeping it in tow mode as I don't trust that the big bang in other modes isn't going to harm anything. They also probably know that if they were to keep it, they'd have people lemon lawing these all day long since they can't get the parts within 30 days, have no loaners, and the local rental companies have limited inventory to rent out.
 

bball3

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No problem, good luck. I just started on week 6 of waiting for a part. Dealer ordered it and gave truck back, said it's fine to drive until it comes in. Keeping it in tow mode as I don't trust that the big bang in other modes isn't going to harm anything. They also probably know that if they were to keep it, they'd have people lemon lawing these all day long since they can't get the parts within 30 days, have no loaners, and the local rental companies have limited inventory to rent out.
they’ve had mine for almost 30 business days with no end in site. I am in a rental (they also have no loaners), but I’m beginning to wonder about options for invoking the lemon law.
 

Singblaze

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they’ve had mine for almost 30 business days with no end in site. I am in a rental (they also have no loaners), but I’m beginning to wonder about options for invoking the lemon law.
I am waiting on the same part. I am still driving mine, but only in tow mode. Same here with the lemon laws.
 

bball3

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I am waiting on the same part. I am still driving mine, but only in tow mode. Same here with the lemon laws.
I’m on the phone with Ford now. FYI you can put in a request for the buyback plan with no effect on your existing parts and warranty work. And it’s your choice whether or not to accept their offer should it be approved.
 

Litebulb

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Glad to join in, mine has done it 3 total times, the first I didn't know what happened. The second and third time I looked at the dash and saw at a dead stop it was still showing in 8th gear. I have also had a lot of hard downshifts starting in the last 2000 miles. I'm at 31700 ish miles. while getting an oil change yesterday I was chatting up a service writer and the trans tech was up front, they were aware of the issue and apparently, there is a TSB for this issue now that's a "Programming" issue. I go in Monday to let it sit a day
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