What are pitfalls of "hard mounting " tranny vs rubber mounts?

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Sublime one

Sublime one

72 Demon
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so I am at the point in Engine swap that the TR6060 has to fit in the Demon. I have to fabricate the tranny mount and am wondering what is down side of hard bolting the tranny support? I do not have a lot of room to create a vibration pad if you will. I have seen a lot of folks simply make the support bracket and bolt it up, but the factory always provides a rubber mount. Likely for a good reason? Any advice or experience would be greatly appreciated. The engine is a 6.1 Hemi backed with the TR6060. Virtually zero mods with exception of headers and CAI. Daily driver 72 Demon.

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The rubber mount is either for vibration dampening or to allow for engine twist/torque OR BOTH!! If the engine is hard mounted to the frame then you should be OK but if the engine can rotate (engine twist) like a stock motor then you might get some breakage around the trans mount brackets/bolts/etc.
 
its a 3 point mount: 2 motors and a trans. If you hard mount any without a pivot, your going to get cracks from torque flex unless you control it (3 hards or a torque strap) Using 2 flex on the motor and 1 hard point on the AL trans will end up cracking it back there. How about motor isolators on the mount where it attaches to the frame? So the whole yoke is isolated?
 
pishta said:
its a 3 point mount: 2 motors and a trans. If you hard mount any without a pivot, your going to get cracks from torque flex unless you control it (3 hards or a torque strap) Using 2 flex on the motor and 1 hard point on the AL trans will end up cracking it back there. How about motor isolators on the mount where it attaches to the frame? So the whole yoke is isolated?
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I am using one of Dennys HDK tubular K frames so I would consider the motor hard mounted? Plus I am using sub frame connectors? So in theory I actually need to hard mount it? Thanks a million guys.
 
I have a engine plate and still mount the trans in rubber. I know of to guys that had solid motor mounts and solid trans mount and still broke the tail shaft housing,
 
My 0.02 from what I've studied and found in forums is that you don't usually mount the transmission with solid mounts. I've read that its more common on more dedicated race car oriented automobiles. But solid motor mounts and rubber tranny mounts are safe.
 
Im not sure about your application, but every 727 iv seen folks use hard mounts to the cross member on end up breaking, whether the engine mounts are solid or not.
 
I would like to add, that small amount of cast aluminum is weak. If its rigid the vibration from driveline would be enough to cause a failure.
Im curious though, is there such a thing as a heavy duty tailstock?
 
White Lightening said:
My 0.02 from what I've studied and found in forums is that you don't usually mount the transmission with solid mounts. I've read that its more common on more dedicated race car oriented automobiles. But solid motor mounts and rubber tranny mounts are safe.
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this ! ^^^^^^^^^^^^^^^^^^
 
NVH
Noise, Vibration, and Harshness
If you have ever run a car with a wrecked trans mount and the trans sitting metal on metal, well there is alotta lotta racket and vibration sent into the floor. And on every shift POW!

That's a nice looking mount tho,
and I'm wondering about the two downlegs, below the hoop. Are those biscuit mounts?
But if you are keeping the T-bars, I see your point, you would need a massive hoop to pick up all the points. Have you considered suspending the trans from two side mounts? Or a top mount even...
There's also no reason you couldn't divorce the mount from the T-bar hoop and move it back further to the rear. The tail is aluminum right; you can weld a bracket on wherever.
Careful not to run out of seat-rail space,lol.
Yeah I see a bit of thinking time for sure. I'm very interested to see how this all plays out.
 
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AJ/FormS said:
NVH
Noise, Vibration, and Harshness
If you have ever run a car with a wrecked trans mount and the trans sitting metal on metal, well there is alotta lotta racket and vibration sent into the floor. And on every shift POW!

That's a nice looking mount tho,
and I'm wondering about the two downlegs, below the hoop. Are those biscuit mounts?
But if you are keeping the T-bars, I see your point, you would need a massive hoop to pick up all the points. Have you considered suspending the trans from two side mounts? Or a top mount even...
There's also no reason you couldn't divorce the mount from the T-bar hoop and move it back further to the rear. The tail is aluminum right; you can weld a bracket on wherever.
Careful not to run out of seat-rail space,lol.
Yeah I see a bit of thinking time for sure. I'm very interested to see how this all plays out.
Click to expand...
At this point I am looking at suspending from the four side mounts, the engineer geek in me says mathematically they will be more than sufficient. The racer in me says I am screwed if I do not go rubber mount. On plus side I am very handy at welding cast aluminum so I am going to mount it hard watch it close and regroup if she breaks. I am building car for wife and she typically doesn't thrash them like I do although she is not above donning a helmet and dropping the hammer at the track! Did I mention she drinks beer and loves to camp in a tent and hunt deer and elk for days on end? And she fishes better than I can? Oh yeah love me a redneck girl! And she patches me and the boys up after hockey games when we try to do things only young hockey players should do. All of which is why I am building the Demon for her as a daily driver.
 
Sublime one said:
At this point I am looking at suspending from the four side mounts, the engineer geek in me says mathematically they will be more than sufficient. The racer in me says I am screwed if I do not go rubber mount. On plus side I am very handy at welding cast aluminum so I am going to mount it hard watch it close and regroup if she breaks. I am building car for wife and she typically doesn't thrash them like I do although she is not above donning a helmet and dropping the hammer at the track! Did I mention she drinks beer and loves to camp in a tent and hunt deer and elk for days on end? And she fishes better than I can? Oh yeah love me a redneck girl! And she patches me and the boys up after hockey games when we try to do things only young hockey players should do. All of which is why I am building the Demon for her as a daily driver.
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And I forgot the two down legs will result in forehead gashs, I have removed them now as my bracketry evolves. I am starting to box it in now, I will try and get some pix today. The two down legs were remenant from OEM mounting plate. I really liked them but the ground clearance was becoming an issue. Thus the side mounts.
 
It will whine like a wounded cat in first and overdrive. She won't like it...unless she likes the sound of a gear drive.
 
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