Need help bad

[91SE]

I just bought a 91 240 (it has hicas because the hicas light has been on constantly) I'm not sure if that makes it the hicas edition. The car has 326 000km(195 000miles) on it hence the reason I paid 900$cdn for it. The problems I'm looking at are the following, when I go over a series of bumps the rear end flops around like crazy(at a stand still the rear is perfectly solid so I don't think the problem is bushings or ball joints) , this leads me to believe that this is why the hicas light is on I'm thinking the canceler will remedy this but if the problem isn't too serious I wouldn't mind keeping the system active. I just noticed tonight that my p/s fluid is a little low but the front steering is smooth and quiet. Also the muffler before the last muffler is falling apart at the seams, I would like to know the diameter of my stock exhaust my engine being the KA24DE. I've tried a search on this but it left me with about five different possibilities. Finally I would like to change the fluid in my diff. apparently it's supposed to be a vlsd and I can sort of vouch for that since I'm yet to see just one wheel spin and spinning they have been. I would just like to know what fluid I should be putting in, I was planning on just going to nissan but if there's an aftermarket fluid that's equivalent or better I'd get it. Otherwise I'd like to say this car is simply amazing I've owned it for only two days and I've already smoked an IS300. I'm glad to finally belong to this club officially and I thank you in advance for the advice.

[Nismo_Freak]

Low P/S fluid will trip the HICAS light in 300Zs... you also could have a rear HICAS P/S rack failure with the milage being that high.

The VLSD requires a LSD additive in the fluid... I'd suggest a good Redline LSD Fluid, but if your on a budget your typical gear oil is fine w/ an LSD additive.

Your rear end wobble issue could be a number of things, unrelated to HICAS.