Aluminum Driveshaft / Conversion U joints

[His Royal Ghostliness]

then the Internet may be right (isn't it always? )

Yeah about that, wonder how many people dropped their diesel's valves down the cylinders following the Internet's advice on when each piston hits TDC - I chose to trust what I can touch instead of what I can read, turns out it was the right choice Measuring driveshafts is quite annoying tho, especially on low-riding cars like the Mk8 - quite often it's a case of you can see the shaft, but that's about it, can't even reach it let alone take some proper measurements off it. The Mk8 is also quite a rare car these days... so I'm thinking this is one area where we don't want the internet to be right, lol

[BlackVic_P71]

I thought I had seen the TC driveshaft swap mentioned by others but that was the thread I know how to find. I know another member went custom for his TC driveshaft.

[gadget73]

The 93 Mark VIII drive shaft is indeed a one year beastie. Don't recall if its because its aluminum or because it doesn't have the double donger universal joint but there is something particular and desirable about it. Those are extra fun because the drive shaft runs right above the fuel tank, requiring removal of the tank to extract the shaft.

Honestly at some point I think we're going to just have to go custom on these things, or just find driveshaft shops that can balance the steel one so it doesn't shake and quake. Personally I could give a damn what its made of, I just have no desire to roll down the road in a movable washing machine on spin cycle.

[knucklehead0202]

^^^Completely agreed. Are most of the vibration problems due to people re-gearing their rearends or is it just a fact of life? My car has 3.55's and drove like a dream at about 75-80mph. No notable vibration that I observed. Obviously I've never had it much beyond that, nor could I tell due to the 85mph speedo, but just wondered if this is a major problem.

[gadget73]

My original drive shaft with factory 3.55 was bad over about 60. The current one starts to pick up some noticeable shake around 75-80. The original had some known yoke damage, the current one I suspect the balancer ring is not really ideal anymore and it needs some service. No reason it shouldn't be smooth at any speed I would realistically drive at.

[His Royal Ghostliness]

Gears have no bearing on a shaft's balancing, altho numerically higher gears do require higher shaft speed to maintain the same vehicle speed so if the shaft is slightly off-balance the effect of that will be noticed at lower vehicle speed. Balancing a steel shaft is no big deal if the person doing the work cares about what they're doing, my driveshaft guy is quite meticulous and did a great job and I have no vibe at 90mph which is about where the engine defuels. I've had another driveshaft made by him, went into a friend's truck, he has not complained about vibrations so I assume all is well there also. Gadget's factory driveshaft will be going to that shop as soon as I locate a suitable yoke for it, that ought to take care of his TownCar's bad vibes hopefully forever.

[gadget73]

right, the faster the shaft spins, the more obvious balance problems become at normal speeds. I guess you might also make the argument for reduced rotating mass allowing for a fairly tiny improvement in acceleration but at our weight and power level I don't think thats an argument anyone can make with a straight face.

[sly]

the shop my transmission shop outsources drive shaft balancing to did a spot on job. There is NO vibration in my car at all up to at least 4300 driveshaft rpm (calculated).