2018 F3T will not downshift automatically - any ideas?

[gjordon]

My wife’s 2018 F3T has decided to stop automatically downshifting. When starting cold it may downshift a couple of times but when it does work, it seems to downshift at the wrong RPM and will lunge pretty hard at the shift. Once it warms up, it will not downshift at all. You can come up to a stop in 6th gear if you don’t watch it. It will manually downshift as its supposed to.

I’ve also noticed sitting at a light you have to apply the brake pretty hard to stay stopped because it wants to go. The idle RPM has not changed since this started and stays at 800-900. It has also died a couple times at a stop but does start right back up.

When upshifting and running at highway speeds all seems normal.

There are no fault codes.

I know it most likely needs to visit the dealer but the closest dealer is 3 hours away and I haven’t been too impressed with their service so far.

I did replace the LH multifunction assembly a few months back for no reverse or manual downshift which resolved those issues.

I haven’t been able to find much of anything on this issue and hoping someone may have a suggestion.

[BertRemington]

will lunge pretty hard at the shift.

I’ve also noticed sitting at a light you have to apply the brake pretty hard to stay stopped because it wants to go.

You have a HCM failure of some sort. The TCM controls the HCM line pressure which control the clutch engagement points. They are obviously incorrect.

Because you are so far from a trusted dealer I would first try a complete oil, engine filter and HCM filter change. I would use the BRP 5W40 oil to establish a baseline. I recommend BajaRon for the filters to ensure you get the correct and complete kits.

After changing the oil and filters drive for at least 100 (200 better) highway miles if you can do so safely. You want to circulate the oil through the filters and through the clutch plates (they have cooling ports) therefore every few miles or so cycle through the gears 6-5-4-3-4-5-6 at least times.

If the symptoms mostly improve repeat the oil and filters change and thank your lucky stars.

If they don't you may have CANBUS problems, TCM firmware problems, TCM short/long term trim problems, dirty or worn HCM solenoids, or failing/disconnected HCM temperature and pressure sensors.

Hopefully someone can provide a better and cheaper diagnosis than mine.

Best wishes.

[gjordon]

Thanks for the reply and the suggestions.

It has right at 22k on it now and close enough for its next oil change. I didn’t have any idea about the transmission filter so I’ll take care of that as well.

Anything outside of that I guess I’ll be finding a dealer.

[EdMat]

This is strictly from memory and I can't find the video. Possible obstruction under a solenoid valve seat and BUDS was used to fully open the solenoid and flush it out. Don't remember if it threw a code but they used BUDS to check the pressure points in the system and found the problem.

[gjordon]

Thanks! I’ll add that and see if I can find anything.

[Yabbadabbadoo]

.... I’ve also noticed sitting at a light you have to apply the brake pretty hard to stay stopped because it wants to go. The idle RPM has not changed since this started and stays at 800-900. It has also died a couple times at a stop but does start right back up....

I had that exact problem. Posted about it last year. The clutch basket central nut came loose over time. Dealer took it apart and fixed it in one day. It's been perfect ever since.

https://www.spyderlovers.com/forums/...t-idle-problem

[BLUEKNIGHT911]

I had that exact problem. Posted about it last year. The clutch basket central nut came loose over time. Dealer took it apart and fixed it in one day. It's been perfect ever since.

https://www.spyderlovers.com/forums/...t-idle-problem

Well I guess you made it home safely ........Mike

[gjordon]

I had that exact problem. Posted about it last year. The clutch basket central nut came loose over time. Dealer took it apart and fixed it in one day. It's been perfect ever since.

https://www.spyderlovers.com/forums/...t-idle-problem

That sounds just like the issue and makes sense but you didn’t mention any issues with the auto downshift. I guess I could have two unrelated issues other than they both started at the same time.

I guess it’s time to find a reputable dealer who accepts my warranty.

Thanks for the tip!