Odd question about replacing motor mounts...

[Maximal]

I can only comment on the solids but vibrations aren't really that bad and only at idle. I have rode in a few cars with Poly's and thought they were solids to be honest.

I would suggest replacing all 4 with whatever you go with as leaving 2 rubber ones will still give the motor more movement than what's productive.

[Chris@Rvengeperformance]

Leave the sides stock. Poly sides drove me nuts.



The front and rear mount to rubber mounted subframes. The sides mount tight to the chassis.






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[sergechronos]

Is anyone 100% convinced about it being less strain on the drivetrain? If anything, wouldn't it be more as you are now transferring more torque (and subsequently more vibration) through the system?

And I'm in Michigan, I think there are 4 people who's cars still run and they are probably still using stock mounts

Compared to cracked/worn mounts, it is less movement. I think the type of torque and stress you are are concerned about would be torsion, however compared to worn/busted stock mounts I would imagine that it is significantly less of a concern to the engine being able to move around in all 3 axis. The vibrations and movement of the engine are still on the engine with factory mounts, even in perfect shape, the rubber and oil just reduces how much of that makes it to the engine bay.

Consider: The engine and transmission are mounted transversally. So with the rotation of the motor and torque, most of the movement is front and back when accelerating and braking. While the front and rear mounts are roll stopped, the tranny and driverside mounts (which are supporting the weight of the engine) are what are absorbing most of the vibrations from the engine running. This is why you could swap to solid mounts front and rear and not feel a bit of it, there really isn't much weight on the front or rear mounts except during the acceleration and braking as they are really just roll stoppers. Factor in the rubber bushings connecting those subframes to the actual chassis and there's just not much to feel. This is also why it is the driver and tranny mounts that are oil filled and not the front and rear, since they have to soak the vibrations up.

Polys will allow less movement forwards and back compared to the factory rubber, and the solids will obviously allow very very little front to back movement. It is this movement that I'm more worried about since any vibrations and such in the engine are just that, in the engine. Polys and solids just allow that to transfer to the chassis (and therefore the cabin). I see no worries about that.

If you have time later, you could search for a study on fluid filled mounts and how they compare. I read it a couple times before, and maybe someone else on here has it bookmarked or similar, and the conclusions were basically that mounts filled with fluids did very little compared to non-fluid filled mounts. My only concern with full solids is that with rubber carrier bearings and rubber bushings on the rear subframe and diff that the front and rear flexing differently could POTENTIALLY do damage (which would be more drivetrain stress as you pointed out) however it doesn't seem to have happened to many people running full solids. Or any people running full solids that I'm aware of actually. I would imagine that if you were to swap all the front subframe and motor mounts with solids you may run into issues, but who knows. The front subframe isn't really designed to move, and the bushings are just rubber to help dampen vibrations and bumps since this is supposed to be a GT car.

It would require a large sample size to know for sure. Although I'm sure if someone running solid or poly mounts up front had resulted in damage they would've already shown up to tell you about it.

If the vibrations are a concern for you, again you could either pour your own mounts, or just get new OEM driver and tranny mounts and replace the front and rear with poly or solids and probably have the best of both worlds.

[aaronatstate]

Is anyone 100% convinced about it being less strain on the drivetrain? If anything, wouldn't it be more as you are now transferring more torque (and subsequently more vibration) through the system?

Think of it this way. When the engine moves in the engine bay, the trans, transfer case, and drive shaft all move with it. By reducing the movement of the engine, you are most definitely putting less strain on the drivetrain.

[j2k4]

Is anyone 100% convinced about it being less strain on the drivetrain? If anything, wouldn't it be more as you are now transferring more torque (and subsequently more vibration) through the system?[\QUOTE]

Think of it this way. When the engine moves in the engine bay, the trans, transfer case, and drive shaft all move with it. By reducing the movement of the engine, you are most definitely putting less strain on the drivetrain.

A stouter leash, as it were.

I think we need to go further with this conversation and define - however anecdotally - the qualities of the different mounts in sets or combinations, by whatever consensus weighs in.

I'm interested in hearing more about an OEM/R&L - poly/F&B set-up, as this is the first time I've heard proper reasonings for it.

I might hesitate at solids, but my wife has RLS, and vibes bother her sometimes.

Since I've been trying to get her in the car for a decent road trip, this is a weighty decision for me.

I've been leaning towards new OEM all around, given I'm BPU and driving the car GT-style, but I kinda like the idea of locking the rocking.

[aaronatstate]

I have Maximal Solid Mounts for the front and rear, and stock side mounts for the engine and trans. My reasoning is the torque of the engine makes it roll clockwise looking at the timing belt side, and I wanted to stop that movement.

[j2k4]

As an aside, I wasn't aware the R & L mounts were oil-filled until now.

Do any of you engineering types know if these share a lineage with the original Hydramounts?

A good friend of mine did most of the development and field-testing for them back in the early '80s.

One of the cooler rides he had to test them on was an early T-Bird Turbo Coupe whose 2.3 4-banger had been swapped for a 5 cylinder Mercedes diesel w/turbo.

He used to lay rubber with it leaving the parts store I was working at - big black cloud trailing behind...

[j2k4]

I have Maximal Solid Mounts for the front and rear, and stock side mounts for the engine and trans. My reasoning is the torque of the engine makes it roll clockwise looking at the timing belt side, and I wanted to stop that movement.

Understood, Aaron.

Translate that into a precis of comparative cabin-comfort for me.

[sergechronos]

A stouter leash, as it were.

I think we need to go further with this conversation and define - however anecdotally - the qualities of the different mounts in sets or combinations, by whatever consensus weighs in.

I'm interested in hearing more about an OEM/R&L - poly/F&B set-up, as this is the first time I've heard proper reasonings for it.

I might hesitate at solids, but my wife has RLS, and vibes bother her sometimes.

Since I've been trying to get her in the car for a decent road trip, this is a weighty decision for me.

I've been leaning towards new OEM all around, given I'm BPU and driving the car GT-style, but I kinda like the idea of locking the rocking.

Almost every transversely mounted engine is the same: Mount on either side by the shock towers and at least one more either on the front bumper side or on the cabin side to triangulate them. Mitsubishi went a step farther and put one in the front and in the back, and did fluid filled rubber mounts for the sides. The front and back are just roll stopped, you should have little (if any change) to interior vibrations from swapping the front and back. The mounts on the driver and transmission side are where all the vibrations go because as Forrest (and others) have said that is directly to the chassis and again, that is along the axis that the engine is rotating.

If you stay OEM L+R you will still have rocking for sure, can't be helped, the rubber just isn't strong enough to lock it down on it's own (not sure even solids could just due to the forces involved). But if you use solid or poly Front and Rears, you are limited the range of motion that it can move front and rear, thus reducing the wear and tear from it.

[sergechronos]

As an aside, I wasn't aware the R & L mounts were oil-filled until now.

Do any of you engineering types know if these share a lineage with the original Hydramounts?

A good friend of mine did most of the development and field-testing for them back in the early '80s.

One of the cooler rides he had to test them on was an early T-Bird Turbo Coupe whose 2.3 4-banger had been swapped for a 5 cylinder Mercedes diesel w/turbo.

He used to lay rubber with it leaving the parts store I was working at - big black cloud trailing behind...

Not sure about lineage with it. OEMs have been trying to years to minimize the vibrations from I4s and V6s due to how they fire, fluid filled mounts was just one of the many iterations that most manufacturers tried at one point or another..

Can't compare a 3000GT and the T-Bird Turbo Coupe though, regardless of the 2.3 4cyl or the 5 cyl turbo diesel, because it was a front engine rear wheel drive lay out. The engine and transmission are mounted longitudinally with a mount on each side of the motor and one between the tranny and frame.