O High Priests of the Rx7,
I have a vibration that is coming from the rear end as far as I can tell. Probably from the middle or right side. I thought it was tires or a bent rim so I just put some used rims and tires on and it still shakes. It is a very minor vibration and it is directly proportional to the speed of the car. Engine can be at 7000 or idling. I don't know what else it could be. The drive shaft and axles seem to spin nice and smooth from running it on the rack. This is my first second gen and I'm totally out of ideas

Please Help

 

How many kms on the car? I had a 83 RX7 that did that and it ended up being the bearings. Im not sure if that is your problem because i could very easly be wrong, but just a guess.

 

Could be many things but here is a quick list of things to check.
1) Bad u-joint on driveshaft or axle
2) bent driveshaft or axle
3) loose driveshaft or axle
4) Worn bushings on rearend
Hope this helps!

 

does it make any noise? Does it change with throttle setting? (ESPECIALLY if it changes dramatically going from light throttle to deceleration)

Probably your driveshaft. It's a very common failure. The u-joints in a stock one are NOT replaceable, but the Mazdatrix aftermarket ones are. Check to see which you have of course.

 

How can I tell if its a drive shaft or axles. I have grabbed onto the u-joints and tried to jerk them around and they won't budge. The car only has 80,000 miles on it as far as the odometer says. The idiots at Midas told me it was a bad differential. Is there any possibilty of that? I have access to a shop and a lift but I don't really know what I'm looking for at this point.

 

rx7ragtop:

Are you talking about light throttle and then letting off?


when I am on the highway I will be cruising around 3500 - 70-75 and when I let off the accel it makes a loud harsh rubbing noise? What is this ?

 

just b/c your ujoints are not loose on your driveshaft doesnt mean it cant be messed up. i just fixed and INSAINE vibration in my car. while acclerating the whole car felt like it was aobut to fall apart, and even with the clutch in the car would vibrate pretty bad. i happen to have a spare drivshaft, so i swaped out driveshafts and it fixed the problem completly. the ujoints on my driveshaft are perfect, absoltly NO slop. I have no idea what caused it to go bad.. maybe it threw a weight off or somthing, i have no clue...

 

how much would it be to replaced the driveshaft, and whats the best way to go about it as cost goes... not meanin to be cheap, but yet effective? i can feel it vibrating in my car also... when i hit higher speeds like 80+ my car gets shakey, and i just had my tires balanced and aligned about 3 months ago... i dont think it could get outta realignment that quick.

 

Does it come from the front of the car or rear? If it is front, check the balanciing again

Townfair tires claimed they ddi my tire. I checked the leds on it, guess what, still the old ones

 

Mine was a bad CV joint. Pick up some rebuilt rear axles. It's not too tought to replace them.