Motor swap - 3400rpm buzziness - MS mounts?
 

New motor and tranny are in and running great. When the original engine was pulled we found one of the stock motor mounts was broken in 1/2. Not uncommon. I had Mazdaspeed mounts put in with the new motor. Now from 3200 to 3600 rpms the whole thing is buzzy as hell. :vash: Rattles the hell out of everything. Under that and above that it's smooth as butter.

Is this typical with the MS motor mounts? Is something else going on? Did I screw up not having the stock crank balanced? This car's a daily driver. With the horsepower I'll be making I sure don't want to put the weak stock mounts back in but damn. It's simply not pleasant to drive around town or on the freeway in that RPM range. I keep finding myself leaving the 6 speed in 5th on the freeway to stay above that rpm range.

Any ideas? Normal and I'm just a puss?

Definitely not the motor mounts. My motor revs smoothly everywhere. Maybe they're not in correctly or the exhaust is hitting on something.
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I didn't hear/feel any major difference when I installed mine when I was N/A. I now have my downpipe hitting my steering column and get tons of nvr.

Thanks guys! I'll get it on a rack and see what I can find. Sounds like something ain't right. Hoping it's something external or not aligned right and not something I screwed up in my build!

Besides something contacting something else what should I look for? How can you screw up motor mount positioning? How would I know if they were wrong? I'll be looking for pics at mnet but any ideas of what else I should be looking for would be great.

I had a very similar problem when I swapped out my turbo. My downpipe would just barely touch the subframe when the car was moving, but you couldn't tell when the car was resting and jacked up. I got a horrible vibration from around 3500-4k that was just unbearable. I got under there and gave everything at least .5" of clearance, haven't had a problem since. I'm sure its something stupid like that.

God I hope you're right and it's that easy! That does sound exactly like what I've got. 3200-3600 the whole car buzzes and rattles.

There's one bolt on the transmission plate towards the middle. I left it out once and it buzzed a bit. Is there a chance you forgot that?

There's a good chance I missed all sorts of stuff! Remember too that AR put the engine in so I wasn't hands on with much of that part. Gotta get it on a lift and look around. I'll certainly add the trans plate to look at as well as motor mounts, exhaust/downpipe and other possible contact points.

You can't look at the trans plate unless you take the transmission off. At least for that one bolt.

Pardon me if I say...

SCREW YOU CURLY!

Don't mess with me...








I'm feeling fragile! :giggle:

;)

:laugh:

:ban?:

No seriously. You can see it in the picture. Ironically this is when I forgot the bolt until the next time I pulled it out, which is the period of time that I experienced the buzz. As loud as you say your buzz is I doubt this is it, sound like something bigger. I just had to prove myself right. You know how it is.
Attachment 196908

Hint: It's right between the #4 freeze plug and the freeze plug on the back of the head.

+1 Grinder FTW

I am suffering from this exact problem Jeff! My DP is just barely clearing the shelf. Actually doesn't vibrate at all until I'm not under load and around 3.5k rpm's . Would you happen to have pix of the things you did to address this? And is it impairitive to take the Turbo and Dp out to make the cuts?

The PO just put in FM mounts and thats wheen it started happening.

Curly,

It's not just a buzzing from one spot. The whole car buzzes and vibrates at those rpms. It's a major resonance issue. There's a whole bunch of buzzes and rattles from it. I'm guessing something funky with the motor mounts or hard contact with the motor/exhaust/tranny somewhere.

Open hood, rev by hand. Sound? Put a 2x4 between exhaust and car near cat. Rev. Sound? Etc.

Oooh! Testing methods to try. I like it. Thanks!

Leave it to a Nederlander to think logically.

Tracked down a couple of the problems. The upper bolt on the BEGI turbo brace for the S4 was missing. The brace was resting against the frame. Couldn't see that with all the heat shielding and such in place. Put the car on a lift and "Oh, would you look at that." Also had some brake lines that were buzzing against the frame at those rpms. Still have a couple other buzzes to track down but it's 80% better now.

Glad for the help, advice and that it wasn't the mounts!

Thought I'd touch base and update once while I'm suffering here in Cabo on Vacation.