For what it's worth. I also strongly believe Jag Specialties (Andrew) is a great choice. I worked with him exclusively for early advice on a suitable donor vehicle, for conversion parts, for technical guidance, and for follow-up smog testing (in California). Would do it over again in a heartbeat.

Andrew helped me put an LT1/4L60E from a 1994 Buick donor into my 1987 VDP. Part of the conversion was building a custom one piece driveshaft manufactured precisely to his specs.

I routinely drive the vehicle at 70+ MPH and have not experienced any vibrations whatsoever. At speed, it's as smooth as I remember the original drive train (but idles much, much, much more smoothly).

 

This has been said many times before and I often wondered why. It just dawned on me. You and many others most likely have 2.88 gears. I've always run 3.54 gears. You'd have to drive about 90 MPH to for your drive shaft to turn at the same rate that I start feeling a the hum.

Conversely a driveshaft in a car with 2.88 gears at 70 MPH turns the same as a car with 3.54 gears at 55 MPH. At 55 I dont feel anything... so I guess that accounts for the difference in experiences.

Since the Sedan was designed with 3:31 and higher gears it stands to reason the Jaguar engineers experienced the same thing as I do at speed and fixed it with a 2 piece shaft.

 

My prior S1, LT1/700R had 4:09 gears... I never felt any vibrations with the one piece driveshaft (nor in any other of my Lumps with various gear ratios). It had engine vibration problems due to the worn out John's rubber mounts that I replaced with Dodge parts... then no vibrations at all..

All my Jags have "seen" over 100 MPH... but, I see no reason one could not do as you explained above and retain the two piece shaft with a conversion = just in case!

 

Seems to me that both ways can work just fine. Seems like, indeed, they do.


My conversion kit was sourced from Johnscars. Mostly because I was working and it came with more bits. Less time to shop up the stuff. Still had to do that, though.


But, Andrew helped me a lot. Some of his stuff is in my car or awaiting installation!


My kit included a one piece drive shaft in steel. Modified from a GM shaft of some model. Clearly not scratch made. Merely a Jaguar type rear to mate to the Jaguar IRS.


I've driven fast. Perhaps 90 MPH or so, not over a 100 as some. But, smooth, no vibrations.


A lot depends on the guy that "make" up the shafts as to being straight and balanced. Spun on a lathe, yes, but how fast!!!!


Carl