Drive Train Vibes

[joemark8]

I will be taking my 98Mark (not an LSC) into a Lincoln dealer for replacement of the driveshaft. At high speeds I get vibrations and it is not my tires. I bought my Mark about two and a half years ago and I have 53,000 on the odo. I have a Premium Care Warranty on the vehicle so it will only cost me $50 deductible. They will need the car for two days - First they will do analysis before replacing the drive shaft. If the analysis validates its the driveshaft they will order it and replace. They say the new driveshaft is balanced and it should be better than the original. While there I am going to ask them to check the Air Suspension System since that has been going on a lot. Is there anything else they should check out i.e. torque converter, transmission & fluid while I have the car there? Or - maybe these things will be checked out as part of the analysis??
Any sugestions will be appreciated.
Joe

 

[Roadie]

Don't let them put an original design shaft in the car or you will have the same problem again soon. The original is a shaft in a shaft "two piece". See if you can get them to substitute a metal matrix aluminum shaft from Dennys Drive Shafts or Dennis. If one of these is installed, the problem will not return. Check dennysdriveshaft.com or call Dennis.
Roadie
95 Champagne Mark VIII
00 Ford F150 Supercab 4x4
02 Mazda Protege
86 Chevy Monte Carlo SS
81 Honda CB900C

 

[TalkRadio]

I guess I'm fairly lucky in that I don't have that bad of vibes coming from my driveshaft. I understand that some Mark VIIIs are worse than others and I guess mine is on the good side of production tolerances.

Anyway, can anyone give me a good, technical reason why guys try to get '93 one piece driveshafts? For years, Ford and others (mostly GM) have used "tube in tube" driveshaft designs. Both Cadillac and Lincoln used tube in tube along with CV joints at both ends. As another example, a '72 Olds Cutlass has tube in tube but the Pontiac LeMans (or GTO) used a single tube. Identical transmissions. Identical rear ends. Identical wheelbases (driveshaft length). Clearly, as GM was going up in their car lines, they applied different techniques to clear up problems.

I guess I'm thinking that a tube in tube design was a practice used by factories to clear up any menacing issues, that the same train of thought would also apply to a Mark VIII. It seems to me that the tube in tube driveshaft would be smoother. The rubber ring separating the two acts as a harmonic balancer. Each tube would have its own natural harmonic and they could very well act to cancel each other. BTW, it was common in Ford products to see an actual harmonic balancer on the front yoke.

Technical thoughts? Technical explanations?