POWERBOOST transmission stays in 8th gear at stop

[Thunderchief]

This is a Powerboost problem but Admin moved my post to "transmissions" -- but it is a POWERBOOST problem.

In February 2022 I bought a F150 Powerboost Lariat. After 39-days the Exhaust Heat Exchanger failed and it was in the shop for 29-days. Today it has started staying in 8th gear when I come to a stop. It takes a bit of throttle to get it moving in 8th gear until I am about half way across the intersection where it will suddenly drop to 1st gear and literally leap the rest of the way across. When it was down for 29-days with the EHE, I mentioned to the dealer that I thought I had met the 20-business day requirement for the NC Lemon Law. He agreed and said he would support me for a buy-back. Next I hear from FMC that I must not have met the Lemon Law requirement since that is what the Dealer told him so no buy back -- it looks like the Dealer had his fingers crossed when he told me he would support me for a buy back. The FMC rep did say they were adding the Premium Care Package to extend my warranty. This is a nice gesture but no value to me since I trade every three years and the gifted extended warranty is not transferrable. Now that the transmission seems to be failing, I believe I am starting over again with the new truck back on the Dealer's lot for an extended period of time. These Hybrid trucks are really a nice vehicle but they don't seem to hold up well.

Does anyone have any ideas about why the transmission stays in 8th gear when I stop at an intersection?

Starting from a stop, like my stop at the Canton, NC traffic light, is normally done with the ELECTRIC motor. So, when you press on the accelerator and little happens, there is no engine noise to alert to a problem. With the transmission in 8th gear there will be a lot of power produced by the ELECTRIC motor with little movement of the vehicle. Suddenly, when the transmission decides to go to 1st gear, there is an enormous jump in the vehicle. Had the car in front not moved out and had I not been gentle on the throttle, I would have climbed the back of the vehicle in front.

This is a dangerous, very dangerous event, and ADMIN ignored that to simply look at it a nothing more than a transmission problem and move my original post to "transmissions".

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[Oxford_Powerboost]

I don’t see the issue with the admin moving the thread - this is a transmission problem, and you’d probably get more response in that section which is why it was moved.

Anyways, that’s not common. The reason for it is that it’s broken and needs repaired. I agree, sounds super dangerous

 

[Orlando150]

This is a dangerous, very dangerous event, and ADMIN ignored that to simply look at it a nothing more than a transmission problem and move my original post to "transmissions".

No matter what forum it is in this is just a fan forum. If you feel the issue with your vehicle is dangerous stop driving it and have it towed to a dealer or other qualified mechanic. No one here can diagnose or fix your issue via the internet.

 

[Snakebitten]

On the 10r80 MHT transmission it sounds like the leadframe isn't functioning properly and so it isn't downshifting in parallel to the speed sensor.
So as you slow down, the truck never downshifts at all? If you dropped from 60mph to 30 mph the transmission doesn't go change to a lower gear?

What about if you manually lock gear ratios out as you slow down?
Or if you put the transmission in manual mode, does it respond to your shift commands?

 

[Thunderchief]

This is a problem that has only occurred twice with both times unexpected. The first time I was stopped at a traffic light where I was puzzled about the vehicle not moving much after adding power. I only had time to check the instruments and watch it jump from 8th to 1st before leaping across the intersection. The second time was in a round-about when I added power coming out of the round-about, noticed little response, and watched the transmission suddenly drop from 8th to 3rd. I talked to the Dealer's Service Manager who said I should make an appointment for maintenance and they would check the codes. He had no idea, he said, about the problem nor did he have a TSB about the matter. I don't want to go through the ordeal of a service event when the expected result would be a CND -- Could Not Duplicate.

I have asked about quirky events with this truck on this site before and received good information. I was hoping that would happen here with my transmission so I had a better sense of the matter before starting the maintenance process.

I thought it a "Powerboost" Problem rather than a "Transmission" problem since the traffic light event transpired with the engine not running -- at least, I didn't realize the engine was running since it happened fast.

I apologize for the agro over my posting.

 

[Snakebitten]

It's a fair and good post. That's what forums are for.

I'd sure be curious about any codes being stored. It sure seems like there should be one or more.

 

[stealth000]

I had this same issue today and it has happened a couple of times over the last few months. I agree that it's a waste of time taking it to a dealer so they could say that they couldn't duplicate the problem.

You may want to consider logging a NHTSA safety complaint.

 

[Thunderchief]

I had this same issue today and it has happened a couple of times over the last few months. I agree that it's a waste of time taking it to a dealer so they could say that they couldn't duplicate the problem.

You may want to consider logging a NHTSA safety complaint.

I sent a note to NHTSA right after my first experience at a stop light. When the transmission finally dropped to 1st gear, I had a bit of power selected with the throttle so the truck literally leaped across the intersection. Fortunately the guy in front of me was far enough ahead that I didn't hit him.

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