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I'm retrofitting m279 engine mount arms to my m275
I'll be retrofitting w222's m279 engine mounts and arms to my w215's m275. I don't wanna replace mounts annually, and w222 mounts don't really seem to fail, from what I'm seeing.
Thanks to @JohnLane for the offhanded w222 comment in my other thread that got the gears turning.
No interest from manufacturers in making m275 poly mounts, and this may be easier than my initial plan of buying a CNC machine.
The mount's bolt holes line up exactly (verified by comparing the arms physically), minus one mounting point, which is still provisioned in the m279's arm... telling me the engineer(s) simply filled in the hole in CAD. If you compare then engine blocks, the m279 STILL has the m275's engine mount arm hole location, they just added another standoff to the block to accomodate the one mount hole they relocated an inch. I'd REALLY like to corner the engineer that approved this change.
I'll be comparing the other mount arm dimensions, and total dimensions with each related mount installed on each arm before moving forward.
The last magic trick will be attempting to have the vestigal mounting hole on the m279 arm machined back in at a shop. Do y'all think that's do-able? I'd just leave both pairs of arms with them for reference.
Also, any interest in buying pre-machined arms? Might as well make a couple more if things work out.
**New discovery, only one engine mount has the goofy relocated mounting hole... they only did that to one of the mounts for some reason. Even more confusing. I only bought mounts for one side to check dimensions. Guess it's time to buy the other.
Another early possibility was these transmission mounts from an AMG GTR, but they're expensive:
Mounting holes looked the same (top aluminum block is screwed into what looks like an otherwise non-altered base), but the mounting surface on the smaller end was not canted, which would require a couple canted aluminum shims on either side of the subframe to rectify.
Update: The arms and mounts appear to be virtually dimensionally identical, from arm mount distance to mount centerline (maybe 1/4* variance), as well as drop height from top of arm to bottom of the engine mount... Time to get a hole machined in the one arm!
The new mounts seem more robust/simple, and their failure mode (should they fail) is superior. The rubber diaphragm is completely encapsulated in the metal lower portion of the mount, so failure-mode engine travel should be considerably less than the 275 mounts. Looks like they took inspiration from the NLA aftermarket '275 mount designs. They do not appear to contain any fluid. They also have a hole in the lower portion of the outer mount, meaning you can fill the airspace below the rubber mount diaphragm with 2-part soft-shore polyurethane. Same with the space above the rubber diaphragm. Vastly superior.
The upper bolt that secures the engine mount to the mount arm is $36 at the MB dealership, which is a bummer. No biggie though.
Update: The arms and mounts appear to be virtually dimensionally identical, from arm mount distance to mount centerline (maybe 1/4* variance), as well as drop height from top of arm to bottom of the engine mount... Time to get a hole machined in the one arm!
The new mounts seem more robust/simple, and their failure mode (should they fail) is superior. The rubber diaphragm is completely encapsulated in the metal lower portion of the mount, so failure-mode engine travel should be considerably less than the 275 mounts. Looks like they took inspiration from the NLA aftermarket '275 mount designs. They do not appear to contain any fluid. They also have a hole in the lower portion of the outer mount, meaning you can fill the airspace below the rubber mount diaphragm with 2-part soft-shore polyurethane. Same with the space above the rubber diaphragm. Vastly superior.
The upper bolt that secures the engine mount to the mount arm is $36 at the MB dealership, which is a bummer. No biggie though.
The stupid expensive fastener is a torque to yield thing. I've been known to substitute grade 8 fasteners with washers and have had zero failures ever.
I expect you will enjoy the 279 mounts. I'm enjoying not needing to replace them annually.
I have an SL65, my motor mounts are shot and need to be replaced. I want to do it myself in my home garage (wish me luck). Do you think that your mods also work on the SL65, I see you have the CL65.
@drlc01 - Having swapped an M275 from a CL65, which came with CL65 mounting brackets, to my SL600, I can say the mount brackets are quite different.
I changed the mounting brackets with the engine completely out and even then it was a challenge as the turbos are in the way.
IIRC, to change the motor mounts you don't have to remove the mounting brackets, but need to raise the engine quite far up off the subframe.
As my picture shows, the top of the motor mounts are very close to the turbos, under the heat shield. Each mount has three bolts on top and you have to lower the mount as you loosed the screws, it is that tight a space. It will be crazy hard with the engine in the car.
mrvedit hit the nail on the head... The engine mount itself may or may not interchange with newer sl65 amg mounting arms, but you'll have to order and compare updated sl65 or sl600 engine arms and mounts to really know if they'll fit. I ordered parts in phases (m279 w222 left mount arm, m275 w215 mount arm), then compared them before ordering the next set.
@JustTXn Could you update with how everything went for you and the part numbers? Going to do these and all of the control arms and ABC lines in that area at the same time.
No updates yet... Bought yet another car, been doing pretty much everything except this because I'm also planning on renewing turbo feed/drain lines and probably rebuilding turbo seals when I go in for the mounts. Big PITA, so I keep putting it off lol.
Arms:
2792230204
2792230304
Mounts:
2222403400
2222403300
**pay attention, there seem to be 2 variants of these mounts. One variant has the removable base plate held in by 1 bolt, which enables installation in my car. The other is one solid piece, which is useless.
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