Anyone mix and match poly with rubber? Runnin poly motor and trani mounts for first time,u definitely feel the 454 rumble thru chassis. Heard some run poly motor and rubber trani Or rubber motor and poly trans or just all rubber? Wont b drag racing, just a once in awhile heavy foot cruiser. Wife doesn't like the teeth chatter.
My experience is once you commit to polyurethane mounts, it's all or nothing. I think most end up mixing and matching due to the fact that all three (or four) mounts aren't always available in poly. I have always changed to poly when I can, and despite feeling a bit more vibration, I never felt it was too much that I wanted to change back. Having every other system in order and no additional vibrations (exhaust, suspension, etc.) helps, too. Like anything else, it's a compromise, but if comfort and the lack of feeling the engine's vibrations is near the top of the list, you should probably stick with all rubber mounts.
Well...sorta. My comment sort of answers your question. Many years (early / mid 80's or so) back, the drag racing class, of "Pro Gas" came to be. I had a short wheelbase Anglia, with a small Chevy in it. In the beginning, about 3/4" of the cars being set up for this class did. At the time, few had big Chevy's. Anyway, Most cars (all engines) had solid (steel) mounts for both the engine AND trans. I...did not. I ran with solid mounts at the engine, but OEM style "rubber" at the transmission. Interesting fact, almost ALL of the cars, at one time or another, had problems with breaking their trans. cases. My car...NEVER broke a trans. case, and I was running as fast / quick as the rest of the cars at the time. I sold the car about 13 years later with...the original trans. in it that I built it with. So...does this answer your question ? FIRST hand experience ! If I were you...I'd run the urethane at the engine, but...rubber at the trans. Mike
Most transmitted vibration comes from the motor mounts not the transmission. Poly is an extremely poor vibration isolation material, which is why its hardly used for motor mounts outside the automotive aftermarket.
Yup. Poly trans mount is only going to increase noise transfer. Poly engine mounts and a rubber transmission mount are fine. Any give in engine mounts will transfer down the powertrain, if transmission mount is as stiff or stiffer than the engine mount that will induce twisting stresses in the transmission. At best, you may get some hang ups in shifts. At worst, cracked or broken case. Unless the chassis/frame is stiff enough, using solid conventional engine and trans mounts will cause case cracking issues. Your competition was using the transmission as a fuse, too bad for them.
With the engine mounted solidly at 3 points, it becomes part of the frame. Any frame distortion or twist will break the weakest point. The aluminum transmission case!
I had a vw rabbit years ago with a nasty little tri carbed motor . I did all poly suspension and motor / tranny mount . I did not like it you felt like the engine wanted to jump out from under the hood !, swapped the motor and trans mounts back to stock and the car drove amazing !
I used solid engine mounts and poly trans mount on street strip car. In the current rebuild - using poly at engine / subframe / trans. If you're not drag racing or road racing - just use rubber all around. Stiffer or solid mounts are really to limit deflection of the mounts to put all power to the ground - particularly on a launch, or hard accel / decel.
Those cars have a torquearm from rear end to either trans or trans mount - don't recall - could be something to do - if the trans mount is seeing that shock load.
I have solid in front with poly rear in two cars and solid front with rubber rear in another, I don't feel any difference and honestly don't feel the rowdy engines either. Maybe you just need better springs and padding in your seat ???
Cool!! thanks for all the whys and why nots, very much appreciated...going to keep the poly motor and install rubber trani. Hate to see any damage inflicted on a mint m20.
Like most unibody cars of the time, the chassis on those are a bit on the flexible side. Those cars basically have no roof structure to keep the car square. Even with subframe connectors T-top and convertible models really need a cage to keep them square. If the engine mounts are solid or poly, those will keep the powertrain from rotating under load. Transmission mount is used to support the tail end of the transmission and not to leave it hanging in space. Rubber trans mount is fine.
I have seen a lot of poly mounts fail in short order, not a fan of them. Saying this I'm note sure where one can buy good rubber mounts.
I've used quite a few poly mounts made by Energy Suspension. They used to make them with the metal portion chrome plated. Looked good on a dressed SBC in a deuce highboy. I never had any problems with them but most of those cars moved on down the road.
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