supersnake67

Ok , well if they dont settle in and the vibration goes away over time then I'm going back to rubber. For now they dont feel that different especially with the added headache.

cliffyk

I think you may be just finding out what polyurethane motor mounts are like. If you want to lose some fillings in your teeth try solid mounts. I had a drag, rigid frame Harley many years ago that could get you off at certain rpms...

supersnake67

Well thanks cliffyk . Thought maybe someone else would second the fact that poly mounts are prone to horrible shakes or RPM specific vibrations, but I guess not. I'm sure there are more important threads to answer like which gears will give me more horsepower 3.73's or 4.10's or what brand spark plugs will get me into the 12's ..........

cliffyk

Funny...

But back to the issue at hand,

Like all systems of joined components the relationship between the engine/transmission mass and the chassis will have harmonic resonances at certain frequencies. The automakers go to a lot of trouble working to minimise these, and/or move them to less perceptible bands, this is NVH, Noise Vibration Harshness, engineering.

Often this requires compromising what we enthusiasts call "high-performance". The arguably over-compliant rubber motor mounts are a good example of that...

supersnake67

I figured NVH would come with the territory and I was okay with that going into it. It just has me confused how it feels like I'm trying to take off in 3rd is the only way I can describe the 1-1,500 rpm vibration I'm getting. Bought them used and even asked the guy if he experienced any vibrations and he said no ....... That's why I'm curious if it's the mounts or other issues. Or he could just be saying no to cover himself . Who knows? I like the power transfer , but I'm just going to get some rubber "anchor" brand mounts to put back in and see if it goes away. Thanks again cliffyk

cliffyk

That is exactly what I found when I had them in my Miata, installing new OEM mounts made it go away.

Some advice from a geezer: do not believe anything someone trying to sell you something says.

Unrelated but good to remember is: "When you buy the cheapest there is there is a very good chance you will get the cheapest there is..."

supersnake67

Very good point. I thought I would beat the system and pay the cheapest price for the best product, but that didn't work either. Live and learn

supersnake67

On a side note just searching for prothane mounts and if others had problems with them. I stumbled on to his screen name (same as his EBAY) on another forum and I guess he was pretty heavy into drag racing his car before it blew up and he started parting it out. Just made me think the mounts were probably WELL USED when I got them.