Just as the title states. The shaking is not constant and it is very mild some may not notice but I notice this happens when the car is running in park. The rpms do not move at all when it vibrates. Is this possible that my recent trans service could cause this?

What's the engine's RPM at idle? Could be too low.

The MB trans service for the 273 engine does not do any work to the engine that would affect the idle. It does require the engine to run to get the oil warm and keep the trans pump in operation...that's it. That's not to say some ham-fisted tech couldn't pull off a vacuum line or electrical connector by mistake!

it is at 600 rpm which is normal I believe. I don’t think it is engine related.. can the trans cause minor shaking like if it is about to stall?

Its remotely possible that the torque converter is not full of oil (they drain it during get process) which could cause some vibration. Take it back and tell them to look into it.

My 2012 a207 E350 3.5 v6 idles when warm at 620 -650 rpm. Might be on yours the throttle body needs cleaning or toss some injector cleaner in the tank when fuel level is low..

Engine mounts or trans mount need replacing.

Thanks that seems to be what the shop said when I took it back they found a cracked trans mount but said my engine mounts were good. The dealer changed all 3 mounts 2 years ago but i'm surprised to see one fail so quickly. Would the trans mount cause vibration in park? I usually hear of vibration during acceleration caused by this.

Also they found a leaking crankcase breather valve which is probably the cause of the smell (also changed by dealer less than a year ago).

Vibration at idle is generally engine mounts. Bumpy roads, acceleration or gear shifting thumps point to transmission mount.

Yea this only happens when in park. But they inspected all the mounts and said the engine mounts were good. I asked the mechanic about it and he said it is because the engine positioning is different when in park. At any case I don't think it costs too much to have a trans mount put in so I'll give it a shot.

im wondering if maybe they did something wrong during the trans service. They said they drained the torque converter. Wouldn’t the new oil they put in cycle through the whole transmission and refill the torque converter too? The vibration I feel in the seat seems a lot like a misfire or about to stall but very mild most mechs don’t feel it and the rpm’s don’t fluctuate at all nor do I have any lights or codes indicating such.

So maybe the old trans oil was degraded and had less viscosity. New stuff up to snuff and takes a bit more power to turn. Rpm drops just a hair causing sl idle roughness that is not apparent when the engine is idling at 620 -640 rpm. Just saying..

yep change the tranny mount, cheap, you be surprised how much vibrations it can cause and at what speed and gear.

Did you ever fix your problem? I have the exact same issue as you described. It is a slight shake that I can feel at idle and I have no change in rpms when the shakes are felt so I don't think it is engine performance related....

I am thinking torque converter, transmission mount, harmonic balancer....one of those 3 but no idea how to test and confirm if they are bad.

Please update me if you fixed your issue.

Trans mount is quick and not expensive at all. I'd do that first. Another diagnostic for the trans mount is a vibration at 30-40 mph under steady speed condition. I think the bad t-mount allows the tranny to move slightly at certain speeds causing minor alignment issues on the driveshaft... causing the vibration.. Prolly the same at idle causing stress on the engine mounts

As far as testing the tranny mount...have the car on a lift and start the car, then place in drive and observe the mount as it gets up to speed slowly to about 40 mph...If it is bad , you will see it moving about.

One way of testing the engine mounts is having the car on the ground, placing it in drive with brakes on fully and parking brake engaged for safety, then slowly raising the rpm. The engine should not move much. if it does they probably need replacing.

Hope that helps

If the vibration started after a trans service it's very possible the trans support crossmember or the exhaust could have been loosened and moved to access the trans pan . Was other service done at same time that could be related? What needs to be done before throwing parts at it ,is to slightly loosen trans and motor mounts and use a pry bar to move and neutralize the engine and trans mounts to see if vibration gets worse or better.Motor and trans mounts rarely fail all of a sudden its a slow process as the fluid in the mounts leaks out . If it was a fluid issue that would be more prevalent under load ,shifting,forward ,reverse etc when fluid pressures would go from high to low.This is in park the trans fluid pressures are at max so its more likely that the trans /motor mounts have shifted causing the vibration and it should be neutralized .It doesnt have to move alot to cause vibration ,but it is not unusual for this to happen .If it moved a lot you should be able to see it by position of bolts on trans crossmember . Most techs would road test car before and after service if the mounts were suspect by road test and visual inspection it should have been brought to the customers attention ,its not that hard .