First of all an needed update is in order. I am the guy whos mechanic accidentally drained the front diff oil and replaced with 75w-90. I corrected this the next day by sourcing some 75w-85 Synthetic gear oil and having the 90 drained and replaced with the correct weight.

Today though I am having issues.

I live in KY and today the weather was pretty cold this morning. I didn't check the temps, but it was probably in the low 40s. I was late for work because it is my birthday and I felt that I deserved an extra snooze on my alarm. So I went outside and started my car up and put it in reverse. Normally I will start it and go inside and drink a very quick cup of coffee whilst it heats up for about 5 mins. However, today I simply did not have the time. Upon Dropping it into R and releasing the brake the car began to reverse as normal as I backed out of my garage. Upon applying the brake to slow myself down as my mirror got close to the garage door framing, the car 'jerked' backward quite hard but with not much force about three times; causing me to fully apply my brake and bring the car to a full stop, stopping the jerking. That worried me but I was late and gave it a second and then released the brake and continued to back out and leave with no more issues. Mind you temps on the trans via the AMG dash menu said the temps were around 13C. So on to the interstate I went about 5-7 mins later. Car seems fine. That is until I came up on a slow mover in the right lane and needed to get around them quick. I pressed the throttle to about the halfway mark, and got over to the left simultaneously, when the car dropped the trans to 7th gear from 9th. The car seemed to shift hard almost doing a "lurch" or like the gear slipped. I almost feel like there was a quite sound it made like a pop from the trans but I can't be sure. Like I said I was in a hurry. The transmission was reading still cold at the this point at 49C with blue numbers. However changed to 50C directly after this issue. I attempted to replicate the same problem twice whilst still on my commute, and was unable to do so.

Anything I should be worried with/ concerned? Or is this normal cold temps causing hard shifts?

Sorry to bother you guys with a long winded post. I have been worried for over an hour about this after arriving at work and it is all I can think about (worry-wart type person.)

Vehicle info:
2018 W205 C43 Sedan
7500~ ish miles
Imported from Canada to US as a used vehicle at 6800 miles.
(I am second owner and yes this car is brand new to me so I am still getting used to the nuances)

 

The diff oil is not the same as the ATF. Maybe you’re overthinking all this.

 

Thank you for your reply, I realize this yes, but was more or less worried that I was experiencing an issue with the diff, and mistaking it for the trans, or maybe experiencing a different a new trans issue. Also wasn't sure if it was normal performance. I read about the "bunny hops" and was considering I may possibly need the update to the TCU and fuel pump that correct it. I am sure there is a capacity that I may be over think something and there is no issue at all, but wanted some more experienced thought since I have only owned the car for about 700 miles myself.

 

Remember too, that letting a cold car idle to 'warm it up' is only going to heat up the coolant...engine oil, trans fluid, etc. is still going to be essentially cold...best method to safely warm things up is to drive it gently for the first few miles.

 

happy birthday

 

This seems to especially applicable to this car, more so with transmission and the first few shifts after going in to gear. At overnight "cold" temps (meaning ambient), the first 2-3 shifts after I get in to forward gears are always a bit more abrupt, especially if you're applying any throttle beyond enough to get to 25mph/neighborhood speeds. After that, the rest are smooth.

As far as your highway experience, I haven't personally had the 7 to 9 gear issue, but I do get the occasional pedal/shift lag when I abruptly need to pass or accelerate more than my cruising speed. I will say I've somewhat been able to narrow it down to happening on hills and when the car would already be naturally downshifting to 7 or 8 from 9. If I do it in the middle of one of those natural downshifts, it's like the tranny says "hey I'm already doing that..great! Oh way you want more? Hold on let me finish getting to 7 or 8 and I'll think about it." Too much throttle and it go all the way to lowest gear, not enough and it's lazy and doesn't know what you want...very narrow gap between the two.

No experience on the reverse issue - that's a new one

 

Letting a cold car idle to warm it up is widely recognised as the worst thing to do for your engine.
All your doing is letting the engine run whilst cold, viscous- poorly lubricating oil is circulating around the engine..
This only wear all the moving components faster.
The best and most efficient way to warm the engine is to drive off immediately and place the engine under light load.
The load is what warms the engine faster not idling with no load.

 

Noted. I guess I was always taught wrong. This is something I will cease immediate.

 

I noticed this to now that it’s getting cold. Normal I guess. They are probably using a higher thickness viscosity in the fluid. It will protect better at higher temperatures but will take longer to warm up in colder weather. This will make the first few miles of driving a little rough with the shifts. Drive in Confort until it warms up. Not as noticeable then. I usually drive in Sport after that. Sport + only on highway or open road with nobody around. Definitely warmed up. Can’t wait to see what Slippery is like when I see some snow for the first time. I’ve only had the car a few months.