Broken Motor Mounts

Hey guys, I wanted to add my experience. 2013 GMC Sierra.
Rough idle in gear, started around 96000. Finally fixed with motor mounts at 126000. I attempted spark plugs and wires twice in that timeframe, MAF, new evap parts, dealer fuel system cleaner. After reading up alot I decided to try the motor mounts. I first replaced the driverside with an H3 mount. I could then feel the shutter more and I could no longer shift to neutral to make things smooth out. Instead of attempting to do the other side with the H3 and risk being unhappy, I replaced both with the original mounts and I couldn't be happier. It's almost like a new truck.

Thnks you just convinced me to stay stock.

Just a FYI, pretty much every vehicle you’ve ever owned prior to the NNBS models with these fluid-filled engine mounts have used solid rubber motor mounts like the H3 mounts. And nobody ever mentioned or noticed vibrations from them. They’re in my 02 Denali. I have an 08 Silverado with the fluid filled ones. Can’t tell the difference. The rubber ones don’t fail. The fluid filled ones do, at a very high rate. Make your choice carefully. Replacing these isn’t easy.

Rocket Man said:

Just a FYI, pretty much every vehicle you’ve ever owned prior to the NNBS models with these fluid-filled engine mounts have used solid rubber motor mounts like the H3 mounts. And nobody ever mentioned or noticed vibrations from them. They’re in my 02 Denali. I have an 08 Silverado with the fluid filled ones. Can’t tell the difference. The rubber ones don’t fail. The fluid filled ones do, at a very high rate. Make your choice carefully. Replacing these isn’t easy.

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Wish I could double "like" this post.

Rocket Man said:

Just a FYI, pretty much every vehicle you’ve ever owned prior to the NNBS models with these fluid-filled engine mounts have used solid rubber motor mounts like the H3 mounts. And nobody ever mentioned or noticed vibrations from them. They’re in my 02 Denali. I have an 08 Silverado with the fluid filled ones. Can’t tell the difference. The rubber ones don’t fail. The fluid filled ones do, at a very high rate. Make your choice carefully. Replacing these isn’t easy.

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Same sentiments here. I went through a few fluid filled mounts. Perhaps I'm the strange one that doesn't like replacing my mounts periodically?

What little extra vibes you MAY feel will only be when idling and they're far easier to deal with than the cost and labor pains of replacing the hydraulic mounts time and again. They'll last a decent while as long as you don't tow much or give it hard throttle. Even then, their life is guaranteed to be shorter than the original style.

Rocket Man said:

Just a FYI, pretty much every vehicle you’ve ever owned prior to the NNBS models with these fluid-filled engine mounts have used solid rubber motor mounts like the H3 mounts. And nobody ever mentioned or noticed vibrations from them. They’re in my 02 Denali. I have an 08 Silverado with the fluid filled ones. Can’t tell the difference. The rubber ones don’t fail. The fluid filled ones do, at a very high rate. Make your choice carefully. Replacing these isn’t easy.

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Troof. When I replaced the mounts on my brother's 181K-mile '05 Sierra, it was mainly just cuz it's a 4WD and I had the motor out. They were worn from age and the rubber was cracked, but they were still plenty solid. IIRC, the ACDelco replacements I installed looked identical to the H3 mounts. I think the only difference may have been the heat shield.

A little bit more "solid" or "firm" is fine for me.

I am just a little apprehensive because I remember when I had my G8, everyone recommended the PPV struts and shocks and said they were just a little more firm than stock. Which was complete BS, it literally ruined the car. Got so many complaints about that thing after that with passengers.

I like the smooth ride it has so don't want to hurt that. If it's just a little more rocky at idle, that's fine. As long as there is no difference while moving, I don't care. It's going to rock a bit more anyway with my headers and cam going in.

ls1frc said:

A little bit more "solid" or "firm" is fine for me.

I am just a little apprehensive because I remember when I had my G8, everyone recommended the PPV struts and shocks and said they were just a little more firm than stock. Which was complete BS, it literally ruined the car. Got so many complaints about that thing after that with passengers.

I like the smooth ride it has so don't want to hurt that. If it's just a little more rocky at idle, that's fine. As long as there is no difference while moving, I don't care. It's going to rock a bit more anyway with my headers and cam going in.

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I've done fluid, H3, and solid atomic poly mounts. Trust me, H3 aint bad. To atomics parts, when moving it was smooth. Solid poly only suck at stop lights.

The only reason I chose to change the mounts was solely because of undiagnosed "rough idle", no clunking, and no problems while moving. I wouldnt have thought the vibrations I was feeling would be motor mounts. A lot of post on the "rough idle" subject state that this is normal for these trucks. I knew that was BS but almost accepted it.

A few people in this thread stated they had mixed mounts (H3 driverside with original hydraulic passenegerside), with no issues. After replacng the driverside with H3 mount myself and having that actually magnify my problem I elected to change both to stock. Not because I like or want to change them out again, but to get rid of any possibility that the mounts were a cause of vibration. I'm not saying that the H3 mounts wouldn't have worked had I done both sides. I just knew that I couldn't cross the mounts off the list completely if I ended up still having a problem. Didnt want to do it all again a week later. I saved myself alot of money and finally fixed a problem I'd been chasing!

I should've taken pictures of the parts I took out, but neither mount looked terrible. Driverside was obviously bad, though mostly intact, it had quite a few .5"-1" cracks and noticeable rust color hydraulic leakage. The passenger side looked 90%, with small cracks but no real signs of leaking. I should've cut it open to see what was left, but it was a long day. I'll never know if just a driverside original mount would have fixed it, but it's all new now.. trans mount too.