After replacing my driveshaft with a Mazdatrix aftermarket, I noticed a lot of rattle-y, grumbly gear noise and what I thought was U-joint noise. Trying to troubleshoot this, I figured it may have been a slightly imbalanced shaft, a bad transmission tail shaft bearing, or something else causing the problem, but for starters I noticed that the shifter boots had been cut at some point probably to facilitate removal of the trans for clutch work. I ordered the following 2 boots from Mazdatrix and installed them last weekend, and they made a SUBSTANTIAL difference for interior noise. I had no idea what a difference new rubber boots would make to keep out the noise coming from the driveshaft and shift lever, and now the majority of the noises come from the back of the car, just like they should.

This boot has a metal cover plate that must be removed and repositioned over the replacement, but the effort it takes to get this done is totally worth it;
http://www.mazdatrix.com/Pictures/g-...hiftBush10.jpg

This outter boot helps to keep noise, water, and road grit from making it's way to the interior of the car. When I took my shifter cover out, I could literally see down the side of the transmission, the driveshaft, and the heatshield that's under there;
http://www.mazdatrix.com/Pictures/g-...ShiftBush7.jpg

If you wanted to be extra thorough, the shift tower boot helps to keep debris out of the shift lever mechanism, and I didn't purchase it when I did the work, but may order one and install it for peace of mind;
http://www.mazdatrix.com/pictures/g-...A-WM-small.jpg

These 3 parts are about $140 shipped, and if yours are torn you're definitely getting noise and vibration transmitted to the passenger compartment. What finally made me pull the trigger was that my shift lever was rattling in 5th gear enough that it annoyed the hell out of me. I am sure glad I changed these, as the car is so much quieter now, I can't begin to describe.

 

I wish I could get them. The SA pieces are NLA anymore. Mine aren't bad but the lower one could use replacing.

 

You could probably fashion something up from heavy, thick neoprene - like a wetsuit is made from - maybe doubling it up. The purpose is to keep out road noise and vibration which is located right under there, as the trans, front U-joint, and of course the exhaust header / collector is right about there, so it's a nexus of sound. I actually slowed down yesterday on the way home just to enjoy the nice quiet ride a little longer.

Driving it again today, I'm realizing all new creaks and squeaks that I never noticed before! Seriously, it's worth doing.

 

SA - boot fun fact (can't speak to FB)
If you leave the gear shift in SECOND when parked, this is the position that LEAST stresses the rubber boots. In neutral, the boots are actually stretched, ironically...

Stu Aull
80 GS
(w/new boots)
AK>AZ

 

I would not be surprised if it was designed that way. I was always taught to leave a manual vehicle parked in gear anyway, for safety reasons eg collision into vehicle while it is parked.

PS good post and reminder to put in new ones while I've got my transmission out.

 

Awesome thread, thanks for posting the info. I agree, running without the inner boots is a serious no-go. I need to refurbish both of my boots for next season.

 

Here's the url: https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F28 2737696429

If ANYONE GETS THIS TO FIT AN FB, LET ME KNOW, MY FLOOR PLATE HAS FOUR CORNER HOLES, THIS LOOKS DIFFERENT...

 

Many places., including Mazda... also has the insulation that lays over that whole assembly.... I believe that helps a lot with the road noise...
Just my .02.

Sam