Sarang

Hello all,
Decided not to sell my baby 2012 E350 sport after I got my vette but now i'm trying to resolve an issue I started having . I originally thought it was just the car bass that was making a bumping sound, but have now diagnosed it myself as to being an issue when the car is in 6th or 7th gear. When i'm in Gear 6 or 7 the car makes a sound as if im going over a bumpy road.

Checked the following:

• I've already had the rims and tires checked (not cracked)
• There is no loss of power and car idles quietly and is quiet driving, until I hit the gear 6. I tested this out numerous times by driving in paddle/manual mode and automatic where it starts happening at around 40-50mph. Shifting is not jerky at all and shifts just fine smoothly. I'm pretty definite its a trans issue though.
• When the car makes his bumping kind of sound the car does not shake, it just makes the sound. I've only put costco and shell 93 gas with periodic injector cleaner. I dont think it is a dirty fuel injector.
• Got spark plugs changed at 60k and transmission fluid at 40k. Car is currently at 98k miles. Never had an issue with the car except ripped seats which got fixed under warranty

If any of you guys have any ideas or want me to check anything please let me know. I tried looking at other threads and didn't see any like mine.
Thanks!

nc211

Have you ever had the transmission mount changed? Engine mounts?

I had mine done around 45k miles (currently 73k) back in 2019 (car is a 2014). Under a very light load, when the car would go into 5th gear, I would feel a quick rumble under the car. It wouldn't last very long, just a split second, but you definitely noticed it. When I had the mounts replaced, both the engine and especially the transmission mounts were notably compressed down after 5 years of holding the weight. The problem went away and has never returned. I think the issue was, when the transmission would shift its weight to engage 5th, it was just enough to compress the weakened transmission mount down to the point where metal on metal briefly touched.

If you do go this route, while you're at it, I would also replace the two rubber flex discs at the ends of the drive shaft, and might as well get that center bearing in the middle of the drive shaft while you're at it. I didn't do that back then, but think I need to now. When it comes to the rubber, it's just as much about the age as the mileage, if not more.

Sarang

I actually have not changed the engine mounts and I don't think i've ever seen it on the maintenance sheet
or a known issue in any threads here. I'll look into it

nc211

Mounts aren’t on a maintenance schedule. They just wear out over time and when they’re done, you get vibrations and noises. They are an issue for the 212 but not a major one. Do some searching on here and you’ll find sone threads about it. On the 212 for the engine mount, one of the causes for wear is the heat of tbe engine and it being a compact engine bay.

Honest on your car at this age, if its still on the original mounts, then I would absolutely start there before doing anything else.

Sarang

thanks thats very helpful! i'll call dealerships and indy shops on Monday to see. should I do transmission and engine both together?

nc211

I would certainly do them both at the same time.

easy way to check the engine mounts (two of them) is to pop the hood, start the car, snd habe someone hold the brake and shift the car between drive and reverse. If you see notable movement of the engine, its a clear indicator of the engine mounts.

i will say this too - once replaced, the car will feel wonderful to drive again. Tight, quiet and just great again. Made mine feel nee again!

Left Coast Geek

the transmission mount is effectively the 3rd engine mount. the engine+transmission assembly is held in place by 3 rubber/hydraulic mounts. the 'engine' mounts are on either side of the bottom of the engine, and the transmission mount goes across underneath the back of the transmission. IMHO, you should always change all 3 at once as if the engine mounts are shot, the trans mount isn't far behind, and its easier to replace anyways.

Sarang

Tried this and no movement at all. Still might just get them all replaced

nc211

Unless if it’s something obviously broken from the naked eye, I am willing to bet that any reputable mechanic who knows the brand, is going to point directly to the mounts first. Rumbles and grumbles such as this tend to be mount related, especially when the current mounts are nearing a decade of age. That’s really on many cars in general. I would certainly not focus on anything else as a first step.

Sarang

Thank you guys!!! I got both changed and I cannot believe the difference. Sounds are all good now. I cant believe how quiet is on crank now and driving in general. Hands down I had no idea how much these mounts did and how great it was to change them. I spent 950 on all 3 mounts with tax here in Atlanta and its worth every penny.

nc211

Excellent, glad to hear!!

Nothing ages a car’s driving experience faster than wearing out motor and transmission mounts!

W205C43PFL

Ah that explains why MB calls it the "Rear Engine Mount"