Transmission Thud
Thread Starter
Newbie
Joined: Nov 2019
Posts: 4
Likes: 3
2015 GL550
Transmission Thud
Hi All,
Newbie here. Just got a 2015 550. Very happy except for one thing I am hoping to get some advice on.
When accelerating quickly away from a standing start, I am getting a sort of "thump" or thud from what appears to be the transmission. Best way to describe it is as if the car was in 2nd, and kicked down to 1st as I started accelerating, but not a smooth kick down. Or another way to describe what it is like is if you had the revs at at 1500rpm and then dropped it into drive, just a slight thump or thud. It doesn't happen if you pull away gently or any other time during driving. For example kicking down a few gears to overtake is smooth.
I am still under dealer warranty for another month so want to get it sorted, but any tips of what I could be so I can be certain to get it resolved before my warranty is up?
Thanks in advance
Newbie here. Just got a 2015 550. Very happy except for one thing I am hoping to get some advice on.
When accelerating quickly away from a standing start, I am getting a sort of "thump" or thud from what appears to be the transmission. Best way to describe it is as if the car was in 2nd, and kicked down to 1st as I started accelerating, but not a smooth kick down. Or another way to describe what it is like is if you had the revs at at 1500rpm and then dropped it into drive, just a slight thump or thud. It doesn't happen if you pull away gently or any other time during driving. For example kicking down a few gears to overtake is smooth.
I am still under dealer warranty for another month so want to get it sorted, but any tips of what I could be so I can be certain to get it resolved before my warranty is up?
Thanks in advance
Junior Member
Joined: Oct 2018
Posts: 31
Likes: 11
2013 GL 550
My 2013 Gl550 does the "thud" too during quick acel from start . My engine mounts have been replaced recently, so i don't its related to that. I though initially it was a downshift form 2nd to 1st , but it not that. Feels more like the toque converter locking up to eliminate slippage during acel? Since you're still in warranty I'd take it into the dealer and ask them to diagnose...please update us with what they find.
Junior Member
Joined: Oct 2006
Posts: 32
Likes: 2
From: Treasure Coast, FL
2001 CLK430, '13 GL550
My recommendation is to have the dealer fully inspect/test the transmission and get any data out of the transmission control module...I believe they have to send this data to MB Germany for diagnosis. I may be jumping the gun, but we also had a slight thud on our GL that then became slight "shudder" when lightly accelerating at speed, and ended up requiring a new transmission / torque converter. The thud was exacerbated by worn engine mounts, but it was still there after we replaced those as a first measure. Our GL had 29,000 miles on it but was 1 year out of warranty by age. It was a complete nightmare. The lead tech at our MB dealer was the one who mentioned that he could see that the length of time between gears during a shift, RPM, etc. was out of whack in the TCM data...unfortunately, those measurements were not part of the Pre-purchase inspection we had done at another dealer. After a month at the dealer, we picked up the GL and the tech told me an E-class just came in with the same issue as our GL.
I'm not trying to alarm you, but I thought I had a solid truck...always dealer serviced, clean CarFax, PPI passed, 28,000 miles on it, no tow package so strain on the drivetrain should have been minimal, etc. Just get all of the diagnosis you can while it's under warranty...keep ALL of those records as well for when that warranty expires.
I'm not trying to alarm you, but I thought I had a solid truck...always dealer serviced, clean CarFax, PPI passed, 28,000 miles on it, no tow package so strain on the drivetrain should have been minimal, etc. Just get all of the diagnosis you can while it's under warranty...keep ALL of those records as well for when that warranty expires.
Thread Starter
Newbie
Joined: Nov 2019
Posts: 4
Likes: 3
2015 GL550
Thanks all.
I will get it inspected and sorted under warranty and report back when I can.
I did some testing with a more mechanically inclined mate who suspects it might be a U joint or something else in the driveline. Primarily because the rest of the shifts are clean, and if you pre-load the drive train before heading off (brake torquing) there isn't any thud.
I will update when I get the official report.
I will get it inspected and sorted under warranty and report back when I can.
I did some testing with a more mechanically inclined mate who suspects it might be a U joint or something else in the driveline. Primarily because the rest of the shifts are clean, and if you pre-load the drive train before heading off (brake torquing) there isn't any thud.
I will update when I get the official report.
Member
Joined: Feb 2021
Posts: 139
Likes: 47
2014 GL550
Thanks for following up on the repairs. I found the thread looking for some answers. My truck GL550 has the thud and I knew it was engine mounts since the engine can be seen lifting when torque braking. I am waiting for the shop to take me in for the repair. But the 2nd to 1st kickdown coasting to stop, with the right timing pressing the accelerator gave it a thud. Hoping the mounts will solve the issue on mine too. Do they sell heavier duty motor mounts?
Last edited by Ricardoa1; Feb 23, 2021 at 10:39 AM.
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MBWorld Fanatic!
Joined: Aug 2012
Posts: 1,047
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From: Florida
Too many german broads
Thanks for following up on the repairs. I found the thread looking for some answers. My truck GL550 has the thud and I knew it was engine mounts since the engine can be seen lifting when toque braking. I am waiting for the shop to take me in for the repair. But the 2nd to 1st lockdown on coast to stop with the right timing pressing the accelerator gave it a thud. Hoping the mounts will solve the issue on mine too. Do they sell heavier duty motor mounts?
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Member
Joined: Feb 2021
Posts: 139
Likes: 47
2014 GL550
I’d be ok with solid ones if they last at least 100k a little vibe has to be better than changing these every 50k. If towing, forget about it.
MBWorld Fanatic!
Joined: Aug 2012
Posts: 1,047
Likes: 174
From: Florida
Too many german broads
Yeah seems they don’t last past 50k, what’s the wires on some of them, is it a service sensor? Mine is not throwing codes. Dealer just called to grab my truck back the mounts are on back order, surprise surprise. I’m hoping for the thud mentioned on the thread when downshifting 2 to 1 at coast, highway vibrations 60+ and a suspension clunk (maybe shock) to be resolved with just mounts, before moving to those other areas.
I’d be ok with solid ones if they last at least 100k a little vibe has to be better than changing these every 50k. If towing, forget about it.
I’d be ok with solid ones if they last at least 100k a little vibe has to be better than changing these every 50k. If towing, forget about it.
Member
Joined: Feb 2021
Posts: 139
Likes: 47
2014 GL550
I took a look under and removed the belly shields to prevent the shop from loosing the screws or damaging them. While down there The exhaust mid pipes with cats need to be dropped, then the intermediate shaft from transfer case to front diff needs to come out, there is a cross member supporting the transmission and transfer case that probably needs to me moved to give access to removing the intermediate shaft, But not sure If overly necessary. The aluminum cats/exhaust shields needs to be removed, those looked easy. That should give you access to the mounts. The two bottom bolts you can see from through the K support and are easy. The top seems to be tricky. you have to lift the engine somehow, Either an engine hoist or carefully from the pan with a jack.
DYI doable but since my trucks is still under lemon law guidelines the dealer will need to pick up the cost.
I avoid dealers at all cost and like to do things myself, likely will need to when I get to 150k
Last edited by Ricardoa1; Feb 26, 2021 at 01:08 PM.
