Trying to find source of metal grind on first acceleration after replacing motor mount.

[RickSelest]

I have and 2007 tahoe, as I was first driving it I notice several noises both a clunk and some metal grinding as I I first accelerate, so I checked the drivers side motor mount and it was bad. One of the tests I did was to accelerate in place with the brake on and it did indeed shift the motor to the right pretty badly. This motor mount was replaced and did fix the shifting to the right problem , motor no longer shifted itself to the right. But after I replaced the drivers side motor mount and began to drive I noticed there was still what seems like metal on metal grind/clunk as I accelerate from start which is strange because I thought I had fixed that issue. Doing the accelerate in place while braking again does show any motor shifting and seems normal. So I am confused as to what this sound is, questions I have are:

if the passenger side motor mount is also bad does this also shift the motor aggressively say to the left like the drivers sides did? Because mine is not doing that..
Does anyone know what this sound could be or have experience with something similar? Other mounts that could be bad?

 

[OR VietVet]

Can you duplicate the noise if you hold the brake and accel or do you have to move when accel to hear it. IMO, I would always change both mounts when doing them. It may also have nothing to do with the noise. I would check the transmission mount as well. If you can power brake it and get the noise then have someone you trust do it and you look for source of noise under the hood or under vehicle. Do you have one of the most essential tools you can have,,, the mechanic's stethoscope?




We recommend that you put all your rig(s) info in your signature so we all don’t have to guess at year, make, model, engine size, trans, rear axle locker…….etc. While you may have posted pertinent info in your first post, you may forget to do it again and the info is needed by us anyway. Makes it way easier on all members that attempt to help, to have that info right up front. It is also recommended that you take a pic of your RPO codes, on the inside cover of the glove box, and post that image in your signature. All this info will greatly help those that will try to help with a problem.


If there is any other info, like upgrades, mods or recent mechanical/maintenance work done, that would be helpful in any post as well. Too many times a question is asked by the poster and after about 10 responses we find out that the poster has done recent work to attempt to fix the problem or work that was done that SEEMS not related to the problem.

 

[RickSelest]

Can you duplicate the noise if you hold the brake and accel or do you have to move when accel to hear it. IMO, I would always change both mounts when doing them. It may also have nothing to do with the noise. I would check the transmission mount as well. If you can power brake it and get the noise then have someone you trust do it and you look for source of noise under the hood or under vehicle. Do you have one of the most essential tools you can have,,, the mechanic's stethoscope?




We recommend that you put all your rig(s) info in your signature so we all don’t have to guess at year, make, model, engine size, trans, rear axle locker…….etc. While you may have posted pertinent info in your first post, you may forget to do it again and the info is needed by us anyway. Makes it way easier on all members that attempt to help, to have that info right up front. It is also recommended that you take a pic of your RPO codes, on the inside cover of the glove box, and post that image in your signature. All this info will greatly help those that will try to help with a problem.


If there is any other info, like upgrades, mods or recent mechanical/maintenance work done, that would be helpful in any post as well. Too many times a question is asked by the poster and after about 10 responses we find out that the poster has done recent work to attempt to fix the problem or work that was done that SEEMS not related to the problem.

Thanks, I will fill out all the details. As fas as the truck is concerned. The noise only happens when first in motion, not during the brake and accelerate test. Wouldnt the brake acell test show a bad pass motor mount?

 

[OR VietVet]

Yes, the same test is done for the passenger side mount. But not for the trans mount. That is a "get your ass under there and look test". When laying under there, push up on the tail shaft of the trans , not with a floor jack-use your muscles and hands. If it separates, you have a bad mount. If you have a 4x4, it will be heavier but doable depending on strength. If is a 4x4 and want to, you can use the floor jack to check but go VERY VERY SLOWLY about it. A good light and eyesight will get you there.

I am thinking you mave have something that is rotating under the hood that is hitting. May also be the calipers and pads releasing when you accel after releasing the brakes.

 

[RickSelest]

Yes, the same test is done for the passenger side mount. But not for the trans mount. That is a "get your ass under there and look test". When laying under there, push up on the tail shaft of the trans , not with a floor jack-use your muscles and hands. If it separates, you have a bad mount. If you have a 4x4, it will be heavier but doable depending on strength. If is a 4x4 and want to, you can use the floor jack to check but go VERY VERY SLOWLY about it. A good light and eyesight will get you there.

I am thinking you mave have something that is rotating under the hood that is hitting. May also be the calipers and pads releasing when you accel after releasing the brakes.

Thanks for taking the time to answer... I thought of the calipers but the sound is very distinct. also the slower I accel the less noise it makes. It even happens when I have slowed down not stopped, to make a left turn... as I am turning you can hear this metal shift. It does not do it when I am slowing down.,

 

[OR VietVet]

Based off of what you just said, it does sound like something shifting and very well could need the trans mount.


4WD: https://www.rockauto.com/en/moreinfo.php?pk=9353704&cc=1433255&jsn=2368

RWD: https://www.rockauto.com/en/moreinfo.php?pk=9353684&cc=1433255&jsn=2369&jsn=2369

 

[R3cord303]

I did the H3 motor mounts put in mine- they’re not oil filled, all rubber. Doing that actually fixed the engine shifting issue, and several dash rattles all went away because of how much it shook

 

[OR VietVet]

Good call on the H3 mounts.

 

[RickSelest]

Yes, the same test is done for the passenger side mount. But not for the trans mount. That is a "get your ass under there and look test". When laying under there, push up on the tail shaft of the trans , not with a floor jack-use your muscles and hands. If it separates, you have a bad mount. If you have a 4x4, it will be heavier but doable depending on strength. If is a 4x4 and want to, you can use the floor jack to check but go VERY VERY SLOWLY about it. A good light and eyesight will get you there.

I am thinking you mave have something that is rotating under the hood that is hitting. May also be the calipers and pads releasing when you accel after releasing the brakes.

Thank you for the all suggestions, it helps a lot. I did get under there and shook it around the best I could. I do have a 4x4. The sound was pretty close to what I hear with how much I could move it but couldn't tell excactly if it would be something I would hear from inside the truck. It squeaked when rocked side to side, couldn't lift it hard enough to see if it will lift up but noise was easy to produce by simple rocking of the trans. Have to assume that may be the culprit, its a cheap part so I will go ahead and replace it.

Can you please recommend the best place I can lift the trans up so I can get this replaced? I don't have a trans jack just a regular floor jack.