lingaraju.g

i recently brought a used 2014 gl450 and i am noticing a hard gear shift from 3 to 4 and the higher the rpm the harder the shift and i can also feel a small jolt to the car body at rpm over 5k and it only happens from 3 to 4 all others are smooth and at low rpm i feel little hard shift and i took to dealer for A service and asked them to check and they said its normal and have not given any clear explanation and i plan on reporting it to MB customer service later on, in the meanwhile i ask a friend of mine who is a retired mechanic and he says it looks like motor mounts, please advice on how to proceed, thank u in advance.

4everalone

Kind of hard to tell, but if it was indeed the motor mounts, you should feel it in other gears too, especially the lower ones. The only thing that comes to mind at the moment is a valve body issue, but that's a pretty rare problem on the 7G-Tronic transmission. FYI, if you can reproduce it at will and only in that one gear, it is most likely a problem and not just the nature of the transmission. I see occasional hard downshifts on mine, like maybe once a month, but I am yet to experience what you're describing.

fabbrisd1

So how many miles on your 2014 GL450 - for A service that would be 10K-30K-50K-70K - which is it ?







If it's 10K-30K you would have Mercedes New Car Warranty - at 50K-70K you would be covered under Mercedes Certified Warranty - if at 50K-70K miles if you bought from Private Party or Independent Dealer - you won't have CPO warranty - so which is it buddy ?

Before anyone gives you a experienced answer - don't you think you just might need to know the mileage on your rig - or do you think forum members have crystal ***** (a pun) or have a drone fleet ?

lingaraju.g

yes i can reproduce it all the time and the higher the rpm the harder the shifting and its only in shifting from 3 to 4 gear ( i am of the impression that because its 2014 model that it has 7gtronic plus tranny), and suv currently has 32490 miles on it, according to VMI all timely maintenance were done so far and its still under factory warranty, not sure if i should take it to an independent mechanic or another mb dealer who can verify my concerns.

fabbrisd1

If you have factory warranty as you clain - then take it to a dealer right away with your concerns - cost you nothing.

Don't be foolish..

lingaraju.g

i did and the dealer checked it when i took my car for A service and i was told its normal at higher rpm's, so i asked here for second opinion. the closest 2nd dealer is 160 miles away from me. before i take it again i wanted some clear suggestions so i can talk to them, thank you.

jlim

Maybe you can insist on riding along with the tech.

fabbrisd1

Bring it back into Dealer #1 - and tell them to diagnose and address the issue on a formal written Service Order - or you will call Mercedes Customer Care... say exactly that

Ancore

Hi!
I have exactly the same issue with the car I just bought. When decelerating from higher speed, on its way the transmission does the "hick-up" on 4th gear in particular.
My mechanic tells it could be solenoid issue, oil, valve body or worse - something mechanical.
I have an appointment on Jan 15th with the dealer, but not sure it's going to work out based on what other dealers were telling me over the phone.
So reprogramming (basically it's TCU) may help, but before they may need to clean the transmission, put new fluid, and then reset the adaptation. If that won't help, my mechanic suggested to take a look inside (particular solenoid may be the culprit).

This issue can be reproduced when there are higher RPMs (by higher I mean higher then 2K which very low I think). But here's a thing. On a Sport mode it doesn't do it when dropping gears, but still rough shifting to 2 or 3 sometimes in this mode. I'm driving in Auto. So I'm puzzled, but based on the symptoms it looks like the Adaptation reset should help.
The previous owner told this is the ECO mode where the highest possible gear is used to save on a fuel consumption. I turned it off and nothing changed. I found showing the steps to reset the adaptation but I'm not sure this does anything at all.

Did you fix yours?

Ancore

There is a thread where people suggest to replace the solenoid with the blue top if the transmission jerks off. Not sure if this is applicable to my case. Hope dealer with tell me exactly what has to be done, not just "let's try this first...".

Ancore

Got back from the dealer today. They were able to replicate the issue, but their diagnostics see no other code than P029900, which is low boost pressure of turbocharger (driver's side). Guided test showed Y77/1 valve does not have correct duty cycle. Vacuum tested waste gates and found the left side leaks down.
Offered solution - replace the left turbo, which is almost $4K, including everything. No TCU codes or anything related to the tranny. They explain that there's not enough air to provide smooth shifting and this is the culprit. I can buy this when I'm accelerating and it shifts down from 5th to 4th to have more power, but when I'm decelerating and it goes from 7th to 4th I'm wondering how it happens at all.

I doubt this is going to help, but who knows... The only concern now is the price. I saw some used turbos from junk yards are around $500 (up to 70K miles on them), plus labor. So thinking of doing that in a few weeks maybe. Any suggestions or thoughts?