Thanks to those who assisted regards my questions on the 88 sov IRS diff..took the plunge and drove 600 miles to look at it, turned out to be a 3.54 ratio and an lsd !! Nice to have a win sometimes!! The guy selling it was a true gentleman, there was no tag on the cover alluding to  ratio etc but he stuck to his listed price  ( $ 175 aust ) and was really helpfull getting it loaded up with me. At this point it is trial fitted to my modified 47 buick chassis, it is looking like its going to mount up fairly easily and give me the ride height and travel i need and room for exhaust etc that was compromised with the cage type IRS . Im using all the factory mount points in both my front and rear Jag installations to minimise NVH . Now to track down some rear shock absorbers on this side of the pond and get to fabricating.


 

Hi guys, im in need of some assistance re an xj40 irs..i have a 47 buick that im rodding, i have trial fitted an earlier cage type jag irs but its marginal for width, and the cage is going to cause problems re exhaust and brake servicing short of dropping it all out. I have had a look at some picks of the xj40 unit, looks to be a better option, i live way out in the sticks and i don't have access a unit to measure up..my key areas of concern are the width between calipers ( buick chassis is super wide) and also i am trying to ascertain if i can move the coil/shock assy from forward of the arm to the rear of the arm as that would suit my chassis and floor layout far better. Also, i need a overall axle width at ride height..the buick is running an earlier xj6 front crossmember soft mounted and i am keen to take advantage of jags work in minimising NVH ..hence i wanted to run the earlier  rubber mounted cage type irs but as i said, not very amenable to my floorpan and chassis .My intention is to utilise the xj40 mountings and crossmember as it is. The buick rear rails taper outward just forward of the upsweep, i think calipers are going to be close to outer rails, maybe i could swap uprights from side to put calipers at rear..chassis doesn't sweep down after axle centreline so i may be able to gain clearance at full travel that way. The car is an Aust Holden bodied 400 sedan, running a  mild Holden 308/th700 , so a ratio in low to mid 3s would be nice..its kind of a luxo rod and i want it to ride nicely and not be harsh. Any help appreciated ! cheers James