LBZ: Vibrations At Idle

[c20elephant]

720rpm seemed a bit to high, just recalibrated the ECM with a 710 rpm, I'll drive it a little longer this time.

Anyone know where you can purchase an EFI cable with a 90 degree connector and 9ft long short of buying one without the end.?


http://www.obd2cables.com/products/...les/cable-j1962m-right-angle-to-open-9ft.html

 

[c20elephant]

The Merchant mounts were designed to keep the engine in place under big power. With stock mounts and big power, the motor would torque over far enough it would rip the boots off the intercooler piping, and hit the hood. Or at least, that is what happened on my truck.

Once I put the MA mounts in, no more popped boots, and no more motor to hood contact.

http://www.duramaxdiesels.com/forum/showthread.php?t=27056

Dave, even with a 90hp tune and about 1500lbs in the bed (good traction) and a good pedal to the metal will pop the boots, no need to ask me how me I know. Just the design alone lends it tying the frame sections together...

Best place to find out is from the guy who designed them, right.?...

 

[DAVe3283]

http://www.duramaxdiesels.com/forum/showthread.php?t=27056

Dave, even with a 90hp tune and about 1500lbs in the bed (good traction) and a good pedal to the metal will do that, no need to ask me how me I know. Just the design alone lends it tying the frame sections together...

Yes, as a side effect, it ties the frame sections together. However, I don't believe that was the intent of the mount, just an unavoidable side effect. The frame strength still primarily comes from the cross member.

 

[c20elephant]

Yes, as a side effect, it ties the frame sections together. However, I don't believe that was the intent of the mount, just an unavoidable side effect. The frame strength still primarily comes from the cross member.

Dave, the 2x4 "cross member" is different than the 4x4 trucks which are tied together much better with the IFS than the 2x4 trucks, so yes it is a "side effect". The 2x4 trucks have a "strap" so to speak which ties the rear sections of the LCA's together and some call it a "cross member" which IMHO it is not. Try jacking the truck by it like Costco did on mine, so a cross member, far from it.

Their was a TSB about a clunking on the 2x4 trucks years ago about the four bolts that held this strap in place and I replaced them shortly after purchasing my truck although I never encountered the noise but did it any how.

After inspecting the strap and frame sections on the 2x4 trucks even with the hydoformed formed frame, built in three sections to be welded together to accommodate the different wheel base trucks it was obvious how the frame sections in the front could flex across a horizontal plane and the motor mounts removed the majority of that flex........

You may not notice the difference on the 4x4 trucks but on the 2x4 trucks a substantial difference....

 

[Chevy1925]

Mike, there is a giant crossmember spanned under the engine directly below and to the sides of the engine mounts. that dinky crossmember you are talking about is not what Dave is talking about.

as ive stated before, mounts do not stiffen the frame. why? cause they are not a solid mount. there is still give in those merchant mounts so they can not effectivly tie the frame in and stop the amount of flex you claim to feel. i can bet you, you felt the engine transferring its weight from the stock mounts flexing, changing where weight placement was. And even still, that change is very minor. it is not your frame flexing like you claim it is and the mounts are not stopping any kind of flex. the mounts would destroy that block if they were built to stop frame flex and any kind of flex occured.

merchant mounts were designed to take place of the stock mounts that continually rip apart from those that towed with a heavy foot or have higher HP and wanted a drop in replacement for stock mounts instead of bolting the mount together as many do here.

 

[c20elephant]

Which way would the frame or frame sections flex or twist across a horizontal plane if I were to remove this "crossmember" on a 2x4 truck.?

Would one side raise higher than other when going around a sharp corner.?
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[Chevy1925]

again, the engine is not stiffening the frame. if it is, you will be seeing a cracked block soon. talking about this crossmember is drawing away from what i am talking about with the engine mounts and block stiffening a frame like you have said.

 

[hondarider552]

Which way would the frame or frame sections flex or twist across a horizontal plane if I were to remove this "crossmember" on a 2x4 truck.?

Would one side raise higher than other when going around a sharp corner.?

Try it and let us know the results, I don't see you doing any road racing here anytime soon to prove this theory of how the motor mounts make the frame stronger lol :angel:

 

[c20elephant]

Try it and let us know the results, I don't see you doing any road racing here anytime soon to prove this theory of how the motor mounts make the frame stronger lol :angel:

Prior to and now the difference you can feel when I back the truck out of the driveway off the sidewalk/rolled curb onto the pavement I can tell the difference. Unless you had driven the truck before and after you would never know other than how stiff the front end is along with 1-1/2" front and rear sway bars, it does ride pretty stiff now in the front and even more so after removing the 4'x8' toolbox in the bed.
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Don't care much for the 1972 4 door Cadillac yacht ride, you guys may like it in your trucks and I can clip clover leafs and long curved freeway ramps at a very quick pace with no white knuckling. No road races just very good stability, safety in a panic (IF I ever do that) situation for a 7500lbs. truck.

I do need a rear track bar as the shackles I installed flex and new leaf spring bushings would help also, I have rub marks from the bolts on the frame....:woott:

 

[DAVe3283]

I switched from stock to MA mounts and noticed absolutely no difference in the front end. Changing shocks always has a noticeable change for me, but the MA mounts didn't affect handling for me at all. But I have a 4x4...

Sent from my FlashScan V2

 

[c20elephant]

Update:

The 4x4 has more mounting positions/bolts for the IFS pumpkin so that will make a difference. Also, the mounts have settled in so I have less rattles/vibrations in the cab with the idle reset to 710 RPM. The driveline clunk that is common on the 2001-2010 truck has not been present since installing the Merchant engine mounts and an Energy Suspension polyurethane transmission mount awhile back and this was expected.

So the combination of the polyurethane Merchant engine and Energy Suspension transmission mounts have done what I expected and then some....:thumb:

 

[N2BRK]

I swapped my driver's side to a MA tonight. The whole time I'm thinking that I need to find the 4 page thread where Mike swapped mounts on the Elephant Well, except for when I snapped a bolt and was bitching as I took out the mig welder, LOL. 5 min delay of game, hahaha.

Yeah mine vibrates the whole damned dash now, and it takes bumps better without the engine feeling like it's bouncing around up there. I'll find an idle that works for me, and I won't go roadracing with my new engine-as-a-stressed-member-NOT, LOL.

Miss ya', Mike! :beer2:

Wally