Now, I may just be crazy, but I just installed a B&M shifter into my 1986 Mustang, and for some reason the cabin noise seems to be a lot louder. I installed everything as per the instructions and common sense, but still this problem arises. Not only does the car seem louder from the inside, but I get a metal-on-metal clacking sound at high RPM and it's almost as if I can hear the friction of the clutch. As well, I can feel the vibrations from the motor when my foot is on the pedal, which is something that I don't recall.
Also, the idle is quite erratic; it idles fine (at ~1000RPM) some of the time, but others when I'm stopped or shifting gears it climbs up to around 2000RPM without touching the gas.
Is it possible that the shifter now sits higher and is hitting the floorboard? happened in my '93. There will usually be a slight increase in cabin noise but nothing major, is the rubber boot still in place? on an '86 you would have had to remove the whole console to remove the boot. As far as the idle is concerned, it's likely a dirty or faulty idle air control motor, or IAC.
As for the rattle.... when you adjusted the positive stops.... did you back them off just a bit? When the shifter handle is in gear, they should not touch the bolts.... It should be a hair away from it. I have found in the past that if the handle touches the bolt it vibrates and causes a rattle.
Also, are you using the stock handle? The stocker has rubber on it to quiet it down. I have used a piece of inner tube between the handle and the shifter (where the two bolts are) and that sometimes helps.
What shifter **** are you using... if it is a solid one, they can transmit sound more than the stock type
The interfearence between the shifter and the body could be an issue also.
Also note.... that I have tried almost every shifter there is on the market and I always found they are louder than stock.
Yeah, I'm usin the stock boots, and ****. I'm using the handle that came with the B&M kit. I kind of figured that the stops shouldn't touch, so they're ~2mm away from the shifter.
I took everything apart and tightened everything down, so now the rattling has stopped.