Jumping forward at stop light

[14Mustang]

Anyone else have their truck jump forward like you’ve been rear ended at stop lights?
Started late June been to dealer 4 times with no resolution.
It only does it in electric about 15 seconds after coming to a stop.
Dealer ship figures trans aux cooling pump but I doubt that’s the issue, regardless there are no parts and the truck has been parked as it’s destroying itself.
They gave me a old Gen 12 rental that’s beat.
Not happy I’m paying over a grand a month for a truck that’s non operational.
Anyone have any remedies.

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[JerryLZ]

My old gen 12 did that when I stopped at lights. Apparently you had to keep the drive shaft greased good to prevent it. I never did that. I don't know if its the same issue but that's all I got. Shouldn't happen on a new truck.

I think that was isolated to the 6.5 beds too but that's just hearsay.

 

[14Mustang]

My old Gen 12 did that as well got the splines greased and all good, this is about 50 times worse and something to do with the EV system unloading into the motor uncontrollably

 

[hedge]

the thread below sounds pretty similar.

https://www.f150gen14.com/forum/threads/electric-motor-torque-hit-while-stopped.6984/

 

[Snakebitten]

Curious if your truck had downshifted to first gear when you came to a stop? Or was it still in a higher gear, like 8th?

 

[Viper]

Bruce (SB),
I have a service appt on Monday at 8am for the 8'th gear problem plus harsh down shifts. Do you have any more information on this issue?

 

[Snakebitten]

Bruce (SB),
I have a service appt on Monday at 8am for the 8'th gear problem plus harsh down shifts. Do you have any more information on this issue?

Honestly, I only know what all you good gents share here concerning. And I wait anxiously for you to get a remedy. That's not an issue that I would want my truck to experience ongoing. If there's a workaround while waiting, at least I wouldn't feel like driving the truck was harming it.

Good luck to you with your appointment.

 

[Viper]

Thanks, my work around has been to either use Tow/haul mode, or in Normal mode lock out 8-9-10, or if I forget and it happens, I shift to Park for a few moments when I can, if not I start a rolling take off going very slow as it will sift to 1'st then to 3'rd. If going slow enough it won't slam gears, but until I figured out the above, I thought the trany would fall out of the truck as it slammed extremely hard.

 

[PowerboostedF150]

Anyone else have their truck jump forward like you’ve been rear ended at stop lights?
Started late June been to dealer 4 times with no resolution.
It only does it in electric about 15 seconds after coming to a stop.
Dealer ship figures trans aux cooling pump but I doubt that’s the issue, regardless there are no parts and the truck has been parked as it’s destroying itself.
They gave me a old Gen 12 rental that’s beat.
Not happy I’m paying over a grand a month for a truck that’s non operational.
Anyone have any remedies.

I have had the same experience. New to me ‘21 PB with 64k on it. When stopping at a light, about ten seconds later, it moves a little with no change in brake pressure from me. Very much like a light rear end collision. If this is a powertrain issue the I would like to hear your resolution! One thing I noticed, If you turn on brake hold, it doesn’t do it. In fact I find I am holding the brake harder than I need to in my 2011 year explorer, both due to this issue and the forward pressure the truck has when stopped.

Since there are other issues with this transmission, hard shifts, etc… it would not surprise me if it was something to do with the electric drive motor disengaging from the torque converter (if that is the case, I don’t know if the motor is before or aft the TC.

 

[astrand1]

Yeah that other thread I think describes it but it’s a pressure change from the auxiliary trans pump. Other have got it replaced. Mine does this on and off. I’ve not been able to find out an exact situation to make it do it. I use auto hold so my foot is never in the brake once I’m stopped. It’s not a huge deal for me and I’ve got plenty of warranty so I’m going to wait a bit and see if maybe a future software update might fix it.

 

[ryanc111]

Yeah that other thread I think describes it but it’s a pressure change from the auxiliary trans pump. Other have got it replaced. Mine does this on and off. I’ve not been able to find out an exact situation to make it do it. I use auto hold so my foot is never in the brake once I’m stopped. It’s not a huge deal for me and I’ve got plenty of warranty so I’m going to wait a bit and see if maybe a future software update might fix it.

Replacing the aux transmission pump fixed the issue for me.

 

[thebigdu]

Replacing the aux transmission pump fixed the issue for me.

Just curious... Did replacing the aux trans pump fix anything else? Or was your only symptom the one described in this thread?

 

[ryanc111]

Just curious... Did replacing the aux trans pump fix anything else? Or was your only symptom the one described in this thread?

It fixed the lurch at a stop light and it fixed the chirp I heard when it switched between electric and ICE. It didn’t fix the coolant issue which was finally addressed with the heat exchanger replacement.

 

[14Mustang]

It fixed the lurch at a stop light and it fixed the chirp I heard when it switched between electric and ICE. It didn’t fix the coolant issue which was finally addressed with the heat exchanger replacement.

How long did it take for the dealership to get the pump, my truck has been down now for 4 months with no eta for parts, granted they put me in a beat up old rental but I didn’t buy a 90000 dollar truck to drive a 20000 dollar truck .
At what point should I be cutting my losses here?

 

[ryanc111]

How long did it take for the dealership to get the pump, my truck has been down now for 4 months with no eta for parts, granted they put me in a beat up old rental but I didn’t buy a 90000 dollar truck to drive a 20000 dollar truck .
At what point should I be cutting my losses here?

It was late spring for me and the wait was 4-6 weeks if I remember correctly. Regarding cutting your losses, I feel your pain (this was the first of two extended periods of downtime) but for me it came down to 'then what?'. I was offered the ability to apply for a buy back but it didn't make sense to me. Aside from the upgrades I had already done to my truck (i.e. lift, lights, etc) even if I got back what I paid for it I couldn't get in to a new truck for a reasonable price so the 'losses' in my case were too large to stomach. I bought an extended service warranty and am planning on riding it out.

Ford corporate did end up offering to cover a couple of truck payments and a maintenance plan as compensation which while not equitable in my mind it did help.

Good luck.

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