89mulletbird

iTrader: (1)

Everyone with an S60 should immediately buy one of these:

https://www.markwilliams.com/39014.html
and these:
https://www.markwilliams.com/39112.html

I'll send you my paypal address so you can buy me a beer when your vibrations go away. I had strong vibrations coming through the floorboards above 80MPH. I put the car on jack stands and I could feel the vibrations in the rear end and torque arm. When I flipped the driveshaft 180 degrees the runout at the rear of the driveshaft would change by 0.004" which tole me my cast S60 pinion yoke had between 2 and 4 thousandths runout. I just put this billet yoke on and all of my floorpan vibrations are pretty much gone. I still have a touch of vibration in the shift handle, but I'm going to send my driveshaft back to the builder for a rebalance and I should be all good.

z-maro

iTrader: (18)

Did you ever got your vibration issues resolved? Sounds like I have about the same setup (T56, MWC long T/A, S60 rear). I started with ~3.5° operating angles, and a bad vibration above 55 mph. I added shims under the trans mount (must have compressed the rubber bumper in the trans tunnel a bit). That got my operating angles to 3.2° (trans 2.85 down FtR, DS at 0.35° FtR, and pinion 2.85° up FTR) and helped reduce vibrations a bit while shifting them above 60mph. It is still very noticeable as the rennonance causes the rearview mirror to vibrate and rattle. Obviously most sources say to have to have the operating angles at 3° or less (but greater than 0.5°).

I have looked at many of the other recommendations here (and many other threads) but can't determine what action to take next other than just guessing and checking on the pinion angle. As you mentioned the most logical thing seems to be a need to space the rear end down (raise the rear ride height), but that doesn't seem like the most desirable. The rear has a billet pinion yoke, so the above recommendation hopefully isn't needed. Also DS appears to be phase correctly, as when using a digital angle finder on the slip yoke and rotating the DS to get 0° LtoR, the rear end pinion also is 0°.

I have been measuring from the slip yoke "ear" and did notice that has ~0.3° slop if I push up on it. I also have been checking angles by only jacking up the rear of the vehicle and then setting the axle tube on jack stands to load the suspension. The measurements above are taken by subtracting the angle of the car (SFC angle was validated to be 0° with the car sitting on the ground). It is not a very fun process without a lift.

I also noticed the vibrations increased when I switched to the MWC TA and trans X-member with the original 10 bolt years ago, but nothing this bad. Now I'm unsure if I had the pinion angle was my issue then, or if there is a possibility of misalignment from left to right of the trans output causing issues.

98cherrySS

iTrader: (2)

Man, I know this battle well. I did the following to eliminate my vibrations.

Rubber LCA bushings
Rubber panhard bushings
Rubber (AC Delco) trans mount
Seals-it elastomer heim joint used at TA
Denny's driveshaft
100 tiny drive line angle adjustments until I hit the sweet spot.

z-maro

iTrader: (18)

Thanks for the reply, it is not fun or fast making all the adjustments without a lift. Were you able to completely eliminate the vibrations with those changes?

I have the "stock" SLP firehawk Bilstein level 2 bushings (which I understand should be "1LE" versions) for the LCAs and panhard, same for the trans mount. I have the seals-it end for the torque arm but haven't gotten the linkage modified to be able to use it, I'll give that a try. Driveshaft is brand new from MWC (they subcontract out to PEM) with the sonnax yoke.

Any idea on your pinion angle and operating angles for me as a starting point?

98cherrySS

iTrader: (2)

No lift here either. Honestly, I tried to make the driveline angle as straight as possible to start with and just added pinion angle one small adjustment at a time. Eventually I found the sweet spot. The seals it end eats up 95% of the audible clunking.

z-maro

iTrader: (18)

Interesting. Oddly enough the clunking I used to get from the MWC TA/X-member went away after my S60 install. My big issue is the vibration starting around 60 MPH causes a resonance so bad that my rear view mirror rattles, along with the console/dash at times.

JohnnyBs98WS6Rag

iTrader: (1)

No, I've not made any progress on this. I just set it at what seem to be the quietest setting across the upper speeds and rarely go that fast. I do hear some new noises from the trans that I didn't before the S60 swap. I have a stinking suspicion that my new DS is cut just a 1/4" too long and is causing some binding in the trans under nominal conditions. If so, that can't be helping the vibration issue. I plan in taking a closer look at this next year when I have more time.