vailG63

Has anyone experienced transmission issues with their 2019/2020 G63? A couple days ago I was on the highway and went to accelerate up a steep hill at roughly 60mph. I was driving in comfort mode and saw that the car was automatically in 7th. The car tried to drop into 6th gear and made a very loud grinding noise for about 15 seconds. The entire time it made the noise the screen showed it was still in 7th and the revs seemed to stall. The engine never shut off and no warning lights appeared so when I got to flat ground I tried shifting manually. I shifted up into 9th and tried accelerating and the engine lost power. The live read out of torque and horsepower remained at 0 when I floored the gas and the revs stalled at 1200rpm. I managed to drive it home carefully and bring it into the service department at my dealership yesterday. When I brought it in it appeared to be running properly and they said that no fault codes appeared so they are unsure where to look for the problem. Has anyone experienced or heard of a similar issue?
Any help is much appreciated.

streborx

In Comfort mode the engine start/stop function is active. Maybe the G thought the engine was stopped and tried starting it - thus the knashing gear noise. I always set mine to Sport mode as I dislike the engine start/stop "feature". I plan to ask the dealer to shut this feature off. If he won't, I'll figure out a way to hack it.

JetRanger

IMHO, if this was my G63, no way would I take that car home until it is properly diagnosed, and repaired. Otherwise, if it's a 'no trouble found' situation, yipes, and good luck! You could find yourself in the middle of the Mojave dessert with the car broke down. For a $200k car, no way would I drive her home without positive diagnostics, and subsequent repair. Might be OK with an $11,000 import, but not with a $200k Merc!

JM2C, IMHO, and YMMV

Bob Z.

iTrader: (1)

That would not be ok in any car in the Mojave regardless of the cost! But problems that are not problem when one takes it to the dealer are hard to diagnose.

vailG63

I was in the mountains when this happened and luckily I was able to exit within a couple miles otherwise it would have been about a 20 mile stretch before I could turn around. At the moment I'm being told there is nothing they can do to identify or fix the problem. I'm hoping to find a thread discussing a similar issue on a different model with the same powertrain that identifies the issue. Otherwise I'll have to hope it doesn't break down on me and bring it back in if it acts up again.

300SE1993

Keep your phone handy to document with a video.

Floobydust

Hmmm, seems to me to be something more like a firmware bug in the TCU/ECU because an actual hard error/failure - even a short term one - should have set a code(s) visible to the Star/SDS system.

hard top

Take it to a dealer that has troubleshooting skills. If they drop the transmission pan they would find metal shavings. There is 15 seconds worth of shavings in there.

fabbrisd1

Look... with a copy of that Dealer Service Invoice in hand - which calls out your VIN# - Miles - Date of "Service" (actaully non-Service.

Monday morning call (800) 367-6372 and give them that info - and politely/professionally tell them you have a HIGHWAY AFETY ISSUE that your dealer did not resolve at all - you LOST POWER ON THE HIGHWAY - and you are FEARFUL it will happen again !

Forget the well meaning Armchair Voodoo Wizards here - you a HIGHWAY SAFETY ISSUE - you are a GREAT GUY - and your Dealer Service Dept are sh*tbirds..

Mercedes Customer Care will give you a Report # - and Mercedes Customer Care will take that report and contact Upper Dealer Management for resolution - within 48 hrs you will not believe how nice your Dealer Service Dept will be when they call you to bring your G back in.

Your Dealer Service Dept - their Tech's don't get paid by Mercedes Warranty for diagnosis when you walk in - but UNDER Mercedes Customer Care Inquiry that changes for the Dealer - and that changes it more importantly for YOU !

300SE1993

Now that's some great advice right there. I'm going to keep a mental note of this in case I ever need it in the future. I had no idea about the warranty diagnosis bit, and those keywords are brilliant!

vailG63

Thank you for your advice! I will definitely look into this. The car is still with the dealer and I'm waiting to see if they are willing to drop the transmission and physically look at the gears. If they don't look into it any further at the moment then I think your suggestion is the best course of action.

streborx

Inasmuch as they'll have the truck lifted, have them yank the starter and check the teeth on its gear and on the flywheel.