Drive Train Vibration

[Thumper13]

The problem: I am getting a drive train vibration at 60 to 70+ mph. I had the Hunter Road Force balance done,an alignment ( to my specs ) and double checked tire pressures but the vibration is still there. I happened to wander into BSI ( BIG Miata Spec builder ) and asked Stu about it. He told me that there is a fairly heavy harmonic balance weight on the drive shaft behind the yoke that can separate and cause the vibration. He also said they checked with Mazda engineers in Japan because they had seen this on some of their own Spec cars and on some of their track day rentals. Mazda told him it was for "customer convenience " and only helped eliminate some inherent vibration problems to begin with. BSI then removed this weight from every car they own. They are getting my car next week as I don't have the capability to pull the yoke and do the repair myself.

I have not seen anything written about this condition so I thought I'd post this up for future reference. Stay tuned for pics and a write up. If anyone else has had experience with this please chime in.

[kung fu jesus]

I am ambivalent about those. You mean the Maltese cross-looking piece on the pinion flange? I know move NVH will go right to the pinion gear in the diff, which can lead to failure. What sort of bracing does your car have? Just asking if it isn't the 65mph shimmy...

[Thumper13]

I am ambivalent about those. You mean the Maltese cross-looking piece on the pinion flange? I know move NVH will go right to the pinion gear in the diff, which can lead to failure. What sort of bracing does your car have? Just asking if it isn't the 65mph shimmy...

The vibration is a recent thing. I put about 70k on her and she just started this about 500 miles ago. Cross bracing...just the standard for a 00 base model.

Yes,the Maltese cross looking thing is a steel weight with a rubber core that rides on the drive shaft. According to the guys at BSI these things can separate from their rubber mounting.

[GatorXTi]

Very interested in the results and any DIY input. Mine has been shaking violent at times and with a PDX next Month Im not looking forward to an earthquake simulator go down the fast bits of Daytona.

[Thumper13]

An update. It seems that the OEM driveshaft's universal joint has gone bad. I have a new drive shaft that is balanced ( OEM shafts are not,maybe that's why they need the counter balance weight ) and has a rebuildable universal joint coming in from Miataroadster. It will be interesting to see how much of a difference it makes.....once I get my car back.

[SM16RMSM]

I didn't know there was an replacement option for our drive shafts.

[Thumper13]

I didn't know there was an replacement option for our drive shafts.

949 and Miataroadster both sell drive shafts that ARE balanced with Spicer u joints and they're about half the price of the OEM drive shaft. I believe FM sells one as well but even though they are a GREAT company I think they are a wee bit too proud of what they sell.

Mazda doesn't balance the Miata drive shaft,

[Pfunk]

I've the 949 balanced/rebuildable shaft in my NB; it is noticeably smoother than the old OEM unit it replaced. Whether that's due to it being new or balanced I cannot say but suspect it's a bit of both. Either way, it's nice.