Recommendations for where to buy Motor Mounts

Lacher

Original poster
Member
Sep 16, 2012
24
I just wondered if anyone had any recommendations on what site to buy new motor mounts from. I would like to get them cheap but still decent because I had heard the after market ones do not fix vibration problems. Anyone who has any expierence please let me know....Thanks.
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
The usual discount gm on-line vendor. parts4chevys.com
 

Lacher

Original poster
Member
Sep 16, 2012
24
Does any one know anything about rock auto? I seen them on there for $38 a piece....thanks
 

CaptainXL

Member
Dec 4, 2011
2,445
jeffro312 said:
Rock auto motor mounts aftermarket no good go dealer or roadies suggestion

Is there actually a defect of some sort in the design of the other non-oem ACDelco motor mounts? I am curious what the actual problem is. I would think that if the problem is that they are stiffer then to me that would be a good thing because they are made better.

And also, if there is some type of vibration at idle that is really bad then I would suspect an internal out of balance issue rather than engine mounts. I would be looking at compression, spark, etc... For instance, you don't see engines on test stands hopping around the room due to using no motor mounts.
 

jeffro312

Member
Oct 4, 2012
442
East Haven,Ct
Its a particular 10htz vibration when in gear that signal motor mounts and experience from people who have tried after market have proven factory gm mounts only fix.

Just not made the same probably a bad comparison but we use ac delco plugs because they've been tested and proven so why throw Bosch in if they are known not to solve problem. Get it
 

CaptainXL

Member
Dec 4, 2011
2,445
jeffro312 said:
Its a particular 10htz vibration when in gear that signal motor mounts and experience from people who have tried after market have proven factory gm mounts only fix.

Just not made the same probably a bad comparison but we use ac delco plugs because they've been tested and proven so why throw Bosch in if they are known not to solve problem. Get it

Hmm. At idle 600 RPM / 60 seconds equals 10 RPM's per second. A 10 hertz vibration is 10 cycles a second. I think what most people are describing is a 1 Hz vibration or once a second.
 

jimmyjam

Member
Nov 18, 2011
1,634
CaptainXL said:
Hmm. At idle 600 RPM / 60 seconds equals 10 RPM's per second. A 10 hertz vibration is 10 cycles a second. I think what most people are describing is a 1 Hz vibration or once a second.
what? :confused:
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
CaptainXL said:
Is there actually a defect of some sort in the design of the other non-oem ACDelco motor mounts? I am curious what the actual problem is. I would think that if the problem is that they are stiffer then to me that would be a good thing because they are made better.
The defect is that they are stiffer. Motor mounts are not for simply keeping the engine from departing the vehicle. They were computer designed to damp out a rotational oscillation that depends on the exact mass and resonant frequency of the engine/tranny/driveline/diff/axles/rear brakes. If the resonant frequency of that system is 9 Hz, but the idle RPMs are never below 600 RPM, then the natural resonance of the system is never going to be experienced. The reason that motor mount problems usually (until the mounts are really far gone, collapsed, and stiff) go away in NEUTRAL and come back in DRIVE is that putting the tranny in neutral changes the rotational mass of the system. It disconnects part of the tranny, driveline, and rear axle. So the resonant frequency changes and can't build up to a noticeable level at the 600 RPM idle. For a few weeks while I waited to get my motor mounts in, I just used EFILive to change my idle to 750 RPM and it made me feel better to not vibrate at lights. Not everybody has that tool, though.

The aftermarket vendors never seemed to "get it". That's why in this case, OEM GM mounts are the solution.
 

Lacher

Original poster
Member
Sep 16, 2012
24
This may sound dumb but yes I am a girl......how do I check it at 10hz?
 

Lacher

Original poster
Member
Sep 16, 2012
24
Also are there two or three motor mounts? I have read both just wondered so I can order them for my hubby to do the work.
 

jeffro312

Member
Oct 4, 2012
442
East Haven,Ct
Lacher said:
Also are there two or three motor mounts? I have read both just wondered so I can order them for my hubby to do the work.

You have two motor mounts left and right and a transmission mount. Motor mounts are usual culprit I'm sure it wont hurt to go mount crazy and get tranny mount while your at it although I think that one is more work but not 100%
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
Lacher said:
...how do I check it at 10hz?
The vibration is in the same axis as the crankshaft which runs front to back. The engine rotates more than it's supposed to at idle. If you have somebody sit inside with it in gear, and foot on the brake, the vibration should be at maximum. One good place to look closely at the engine is on the intake manifold, at the bolt noted by the yellow arrow. (not my engine - it's way too clean). See how much it looks like a hummingbird wing, moving back and forth. Have the driver put the transmission in neutral and see the amount of fuzziness go down as the amplitude of the vibration gets less. If I remember right, a good engine will vibrate around 1/4" while in DRIVE, and a bad one is 1/2" or more.

Bring a screwdriver near that bolt head, and as the engine vibrates, it will whack into the screwdriver at the 10 Hertz (10 times a second) that we're talking about. Like a mini machine gun noise.
 

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jaguarjoe

Member
Nov 22, 2012
73
Metalastic is/was a good isolator. My Jag had 11 of them- 4 front subframe mounts and 2 motor mounts attached to the subframe. This gave double isolation from the engine to the cabin. On top of that, the 12 cyl engine was naturally balanced so it ran smooth, very smooth.
The other 5 mounts were for the rear cage and xmission mount.
 

triz

Member
Apr 22, 2013
746
Anyone try GMPARTSDIRECT.COM ? GM parts at a reasonable price.
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
triz said:
Anyone try GMPARTSDIRECT.COM ? GM parts at a reasonable price.
Experience over the years on both forums shows that those guys will advertise parts at exactly wholesale price to sucker you into the purchase if you're only looking at the parts price. Then they rip you on shipping charges. Always compare the "as shipped" price on their stuff. I think they make the majority of their profit on the shipping charge.

The one I buy from is parts4chevys.com, which redirects to GmPartsShop.com - General Motors Parts - OEM GM Parts ? Chevy Silverado Parts - Factory GM Parts. They charge a little more for the part, and a bunch less on shipping, which I believe is a MUCH MORE honest business model that I prefer to encourage.

Compare the two and see if I'm still right.
 

Mooseman

Moderator
Dec 4, 2011
25,482
Ottawa, ON
I've dealt with GmPartsShop in the past, great customer service. They're a real dealership in Phoenix and have a real phone number to call a real parts counter person. Such good customer service that when I ordered a camshaft actuator, they emailed me to confirm that was what I wanted instead of the usual CPAS. When there was a delay in the refund for the core of the old actuator I returned, called them up and fixed it right then.

And they ship to Canada, unlike GMPartsDirect. $121 for the actuator vs. $300+ in Canada, well worth it.
 

jes1888

Member
May 1, 2013
25
so,... what about the tranny mount, is it necessary? mine is at 103k miles as of now and i have this vibration so i need to buy the engine ones, but what about the tranny one? does that one gives problems, fail or something?
 

jimmyjam

Member
Nov 18, 2011
1,634
nah, the trans one isn't going to cause vibration unless its torn. visually inspect it, see if the rubber has cracked and rotted however it should be fine.

The first one to go is the passenger side engine mount, the heat from the exhaust manifold cooks that one way before the driver side.
 

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