ALSFB loud vibration

[sholoveplus]

hey all, I recently installed alsfb's in my 90 sho. The car also has notsoslowsho's reinforced motor mounts, tokicos, and moogs. Right after putting these in, I noticed a pretty loud vibration that fills the cabin, starting around 3500 rpm and continuing right on through to about 6500. let me put it in perspective: you can barely hear the secondarys kick in--it's loud..... So, I've had this combination of ALSFb's and motor mounts on my 91, and my friend has had them on his 95, neither of which had this vibration... I'm stumped......any ideas are greatly appreciated--i don't really mind the sound, I just want to make sure I'm not harming my car
THanks

 

[Ishodu]

Sounds about right, IIRC he had the same issue when he put in those solid mounts. If everything is solid from the engine to the body its pretty common sense that the vibrations will make it to the cabin.

 

[somedude_001]

I refuse to run solid engine mounts just for that reason. don't blame the ALSFB it is mainly in your engine mounts.

 

[NotSoSlowSHO]

These are not solid urethane mounts.

He has a set of my stage 1 mounts. Factory rubber, compressed, and filled with urethane. They are stiff, but not THAT stiff.

In my experience, the rear motor mount contributes at least 75% of the noises and vibes that potentially reach the cabin. So to rule out any other problems, Id remove the rear mount in favor of a stock mount, and see what happens.

If the noise is still there, then you have some other problem that needs to be addressed. If it goes away, then it is nature of the beast. ALSFBs + stiff mounts does = cabin noises.

And yes, my mounts will soften a bit over time. Not a whole lot, but they will soften a bit as they break in.

 

[sholoveplus]

these mounts were actually taken from the 91 and put on the 90; therefore, they have about 3000-4000 miles on them.... the 91 didn't have any where near this amount of vibration--so I'm thinking somethings up with this car.....but I will try the stock mount as soon as I can......I appreciate the advice

 

[tauruswithheart]

hi everyone....im sholoveplus's friend, ive installed 4 sets of of bmalchs alsfb's...including this car.....this is not your normal NVH. its as if something is resonating at mostly between 3500 and 5500. Ive always done the bushings according to shopheonix's website and have never had a problem...im going to slightly lower the subframe (properly of course) and realign and torque to 100 ft lbs and see if the helps, because originally when we did the bushings i forgot my long 1/2 extension to align the subframe so i made do with the end of my tire iron which is not as precise as the 1/2 extension

 

[qiksho]

I have the ALSB's on one of my SHO's and I noticed I needed to torque the bolts that hold them on higher than spec to get them to be "tight". This is/was not an issue when installing new factory bushings or Gen III (which I prefer).

 

[NotSoSlowSHO]

this is not your normal NVH. its as if something is resonating at mostly between 3500 and 5500. I

Check your firewall to rear exhaust manifold clearance.

It sure sounds like it is rubbing somewhere.