thank you to all in the forum who help me so much in fixing my caddy, really saves me time and money. I have a noise in my 1992 brougham that starts at about 20mph it is somewhat of a groaning noise and gets a little louder and changes to a whirring/howling sound. I'm thinking rear differential , the tranny shifts fine and engine runs good also. I bought the car and had a leaking pinion seal so I replaced that and changed out with proper recommended fluid.(dont remember but whatever gear oil service manual said) 80w? I had no noise for six months or more. now I have above. any ideas on what I can do? is it worth just putting in an additive ? what is avail? what would be next step if that doesnt work? thanks for the help steve

DON'T DRIVE IT! Check the rear end oil ASAP!! I lunched my rear axle in my Suburban that way. Pinion seal was leaking and the oil wasn't dripping, it was stuck under the truck.

It had less than 1 qt when I pulled the cover.... The gears were blue in places from heat. It got driven maybe 50 miles at that point from the time noise started.

yeah, I am going to check today, I stopped driving car, I changed pinion seal and it looks dry under car now, I was thinking of using amsoil severe gear 75w synthetic oil if there is plenty of fluid . maybe that would quiet it down some. any comments? or how about the additive for limited slip, even though mine does not have that option, could that help with noise? thanks

I am using the Amsoil regular 75W90 in my Cad. Mine had the factory wrong diff cover gasket, (known issue on many 8.5"s) that restricted oil to the axles. I swapped with correct design gasket and added the Amsoil, and now I get axle bearing noise in corners.

I'll dig into it deeper when I do my differential posi swap soon. It is getting cold, so I need to do it ASAP, I have that crappy Lucas oil in it now, it is worse than having honey in your gears.... (I was desperate, ok? I won't do it again....)

Did any 93's have the wrong cover gasket? I replaced the right rear wheel bearing and axle in wife's 93 FWB not long ago. How would the wrong cover gasket keep oil from getting to the wheel bearings??

Likely ok if you have replaced the gasket, it will get the right one. Look for small rectangular holes on the sides. The wrong gasket (or incorrectly made one) had the holes blocked.

I don't know what years were problems, but in the 90's....