[goatwgn]

I talked about doing this in 2014, but now I am going to bite the bullet and go ahead with it, I believe. I have a Gear vendors overdrive in my '66 Tempest Custom wagon, with mild 455, TH400, and 3.42 axle. When i first installed the GV unit, I had some issues with driveline vibration around 45-55 mph. I had Denny make me up a new 3.5 inch aluminum shaft, and installed adjustable rear upper control arms. The vibrations were mostly gone at this point. But lately, it seems like people travel at higher speeds on the Interstates, as in the 75-80 mph range, and I that speed, the vibration still occurs. Not overwhelming, but still there. I have this car set up to handle well, with Bilstein shocks, rear airbags, a tight gearbox, tall ball joints, custom alignment, and large stabilizer bars. I am now considering a custom aluminum shaft, with the front CV joint, from The Driveshaft Shop. I sent them measurements for a quote on one today. Have any of you ever used one of these shafts in a similar situation?? And how do you like it? I PMd AndrewB back some time ago, and he seemed to have good luck with them, This car has a Trans Go shift kit, and I do drive it aggressively from time to time.

[Schurkey]

The old "Big Block" Toronado/Eldorado used CV joints on the front axle shafts. They were very durable until the boots tore. Those vehicles had ~500 ft/lbs of torque x 2.x for the converter multiplication x 2.48 for low gear multiplication x 3 for the ring and pinion gear--about 7000 ft/lbs or more altogether; but of course this was split between two half-shafts at about 3500 ft/lbs each, and at wheel RPM.

You're going to put all your engine/transmission torque through a single CV, but without the torque multiplication/speed reduction of the rear end gears--less overall torque but higher RPM than the FWD applicaton.

I notice that when The Big Three put "CV joints" in the driveshafts, they didn't use the same style as the FWD axle shafts got, they used "ordinary" U-joints in a closely-spaced assembly; and they tended to do it at the axle end rather than the transmission end.

These are the sort of "CV" joints typically used on driveshafts--and nearly always NOT mounted at the trans end. (Lower two shafts, all three from '60s Cadillacs with center bearings.)
Photo 1. Stolen from http://6364cadillac.ning.com/profile...d-in-1963-1964

[62posbonny]

I have a Driveshaft Shop CV joint driveshaft in my 71 Cutlass. The car is lowered 2", and after swapping in a LS/4l60e combo the driveline angles just wouldn't agree and after rebalancing the driveshaft and adjusting pinion angles half a dozen times I couldn't get rid of a vibration starting at about 65. The CV shaft really is a work of art, and should be for the cost, but after throwing it in the car is smooth as glass to 115 (too old to do too many shenanigans on public roads). It's a tough pill to swallow, but I consider it the best money I have spent on that car.

Just to add, the engine in the Cutlass is an iron block 370 with ported 243 heads, forged pistons and a decent street cam, trans is really well built and have a custom built 2800 stall and 3.73 gears with 285 Nitto NT555G2 tires. Most recent dyno tune was 425hp/400tq at the wheels and I do beat on it up to 75mph quite often. No issues from the driveshaft in the 3 years since I installed it.