Hi, an update now with 8000kms on the car, and a question for any of you familiar with the Jag IRS.
Generally speaking its getting better and better as I work little bugs out. Steadily working on eliminating driveline vibration at higher speeds, and have had a CV drive flange and a CV stub axle made up for the driveshaft and Jag diff by Bettany Gears in Kapiti. I had over 4 degrees of working angle at the diff end which is now addressed by the CV, and now have a remaining 1.6 degree working angle at the front where I retain a standard UJ and yoke. I know around 0.5 degrees would be better at the front but that's as close as I can easily get. That has made a positive difference - it has raised the RPM where I get a pretty bad vibrating resonance with the car running up on stands, which now happens at about 95-105 mph then clears above that. Here are photos of the driveshaft mods.
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When I was testing the impact of this change I spotted that I have pretty major runout on one of the halfshafts in the jag IRS.
I'm wondering if the donor car these parts are from has been hit in the rear wheel where that load would have been absorbed by the halfshaft. When I use a stethoscope there is more noise going on in the rear hub on the offending side than the one running true. I'm assuming I need to swap in a known good second hand replacement before I chase the remaining issue any further. Anyone ever come across this in a Jag rear?
Cheers, Andrew