Ok, just need some ideas here. When I get above 40 mph I am getting a deep bass sound from the car (throttle on or off) and a vibration. Here are the things I was thinking it might be, please let me know if I am missing anything. The car drives fine, just this weird vibration and noise.

1. Wheels need balancing
2. drive shaft imbalance
3. something weird in the rear end
4. transmission wierdness

Any other ideas? I am just going to work down the list and see what kind of things I can find wrong.

 

I hate to ask but do you have a video?

 

I would say its likely option 1 or 2. If either of those dont fix it its possible you have a slightly warped wheel or hub. Common thing to happen on old cars where the wheels are likely to be taken off and reinstalled without proper torquing techniqe. This is more prominent on steel wheels however which in my experience are more prone to warping. I am unsure is any balancing method can take the vibration out of a warped wheel. Maybe a roadforce balancing will help with that one.

 

5: Failing rear u-joint
6: dragging rear brake shoe/pad

First step: check your diff fluid level and condition.

 

Tires rotated/balanced. That was most of it. Found that the front hub is loose, so I will fix that tonight. Good idea on the Diff fluid level. I can knock that out at the same time.

 

without seeing or hearing the car i would suspect a faulty front or rear u-joint on the driveshaft. remove the driveshaft and check for play at the u-joints. also check and ensure your transmission mount is still serviceable, lacking cracks and breaks.

 

^ Same thing happened to me, was worn uni joints

Easiest way to check uni's is put it into 1st, get underneath and try to move the driveshaft by hand at both ends... any play is a bad thing and means they need replacing

 

From mazdatrix.com

http://mazdatrix.com/g2.htm

Transmission / Differential Troubleshooting

This chart is not meant to be complete, or 100% accurate (there are too many variables), but it should give you an idea of what to look for.

SYMPTOM Probable Problems / Solution

Clutch pedal feels weak/dead. Won't go into gear easily. Clutch hydralics. Replace slave and/or master. Possible pressure plate, but be sure of hydralics first.

Very hard to get into first or reverse. Check hydralics first. If was ever accompanied by noise when in gear (pedal on floor) then pilot bearing is not good. If no noise it may still be pilot going bad.

Grinds when going up or down in any one gear. Synchro going bad. Rebuild or replace transmission OR just shift slower and it might last a long time yet.

Grinds in shifting pairs - 1st/2nd, or 3rd/4th Slider hub/shift fork worn out or bent. Rebuild or replace transmission.

Bearing or gear noise in 1st, 2nd, 3rd, and 5th but gone or very less in 4th. Bearings are worn out. Rebuild or replace transmission.

Rattling/grinding noise when stopped, engine idling, transmission in gear, clutch pedal on the floor. Pilot bearing is bad if noise stops soon after transmission is put into neutral.

Rattling/grinding noise when stopped, engine idling, transmission in neutral, clutch pedal on the floor. Throw-out bearing is bad if noise stops soon after clutch pedal is let up. Bearings are worn out if noise gets worse when pedal is let up.

Metallic "Rumbling" or grinding that increases in frequency / noise level the faster you go. Probable rear wheel bearing if noise seems to come from back of car. Possible front wheel bearing(s) if noise is from the front.

Vibration in drivetrain when starting off in first gear, and decreases once car is moving. Front U-joint is bad.

Vibration in drivetrain that gets considerably worse the faster you go. Rear U-joint is bad.

Vibration in car when not moving that increases / decreases with engine RPM. Bad transmission mount.

Really bad noises from drivetrain that change dramatically between acceleration, light throttle cruise, and deceleration. Ring and Pinion are bad. The 3rd member must be rebuilt or replaced.

With Limited Slip Differentials, a "Chatter" on slow speed acceleration AND turning at the same time. We usually can cure this by changing the differential oil to a good grade, AND adding the Limited Slip Additive listed in this web section.


I thought it was a good read. -nick-