strange downshift when going down hill.

[double07]

This happened to me few times. I was going 35- 40mph and during the down hill, I let go the gas. With in the few second, my 06 M35x down shift automatically and the rpm rev up to 4-5k. Is this normal? it only happens when I am going down hill and let go the gas. Thanks for any info and advice.

[ken in az]

yup it's the computer kicking in. gotta keep the foot on the gas or pop it in nuetral like i do

[palincal]

It is the grade logic that is kicking in.

[M4T5]

That sounds like a newer four wheel drive truck/ SUV or ATV 4-wheeler drive train. Is that only for the X model M's? Mine doesn't do that unless you place it in manual mode and downshift it to a few lower gears.

It sounds like automatic decent control using engine braking.

J

[ken in az]

I'm pretty sure that all do this no matter the engine or drivetrain. I know that the ECU and TCM have learning prfiles which depending on driving styles could cause it to happen more or less depending on the user.

[ArbitrageMan]

Theres a spot on my commute every morning where I come over the crest of a hill, the speed limit is 35, and the car downshifts as I take my foot off the gas. Ive gotten used to it, but I used to shift into manual mode right before I got there so it would just stay in the same gear.

Our lexus does this as well, but its not as aggressive as the M.

[NightWatch]

wow, Lexus and Infiniti.... They don't fight when you put them in the same garage do they?

[M4T5]

Better question would be, do they both get to stay in the garage or do they both have to fight for that amenity?If so, which one of them gets all the privileges?

J

[ArbitrageMan]

The lexus is my fiancee's. Guess who gets the garage...

Its funny actually because I washed my M on sunday when it was nice here. Last night it was supposed to rain and snow so I told her I'm taking the garage and I'm taking your car to work today because I'm tired of mine staying clean for one day.

[double07]

Thanks everyone for the info. I did use semi-auto mode to prevent this from happen. I sometime drive it with auto trans mode. That is when I forgot and it happened. I just want to make sure that there is nothing wrong with my trans and it's normal behavior.

[M4T5]

Sorry, but I have never experienced this in my 07 M45. Maybe you guys are noticing this at slower speeds? When does it happen exactly?

J